MIKEBASIN_UserManual

MIKE BASIN

MIKE by DHI 2009

28 January 2010 6:24 am

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Please Note

CopyrightThis document refers to proprietary computer software which is protectedby copyright. All rights are reserved. Copying or other reproduction ofthis manual or the related programs is prohibited without prior writtenconsent of DHI. For details please refer to your 'DHI Software LicenceAgreement'.

Limited LiabilityThe liability of DHI is limited as specified in Section III of your 'DHISoftware Licence Agreement':'IN NO EVENT SHALL DHI OR ITS REPRESENTATIVES (AGENTSAND SUPPLIERS) BE LIABLE FOR ANY DAMAGES WHATSO-EVER INCLUDING, WITHOUT LIMITATION, SPECIAL, INDIRECT,INCIDENTAL OR CONSEQUENTIAL DAMAGES OR DAMAGESFOR LOSS OF BUSINESS PROFITS OR SAVINGS, BUSINESSINTERRUPTION, LOSS OF BUSINESS INFORMATION OR OTHERPECUNIARY LOSS ARISING OUT OF THE USE OF OR THE INA-BILITY TO USE THIS DHI SOFTWARE PRODUCT, EVEN IF DHIHAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.THIS LIMITATION SHALL APPLY TO CLAIMS OF PERSONALINJURY TO THE EXTENT PERMITTED BY LAW. SOME COUN-TRIES OR STATES DO NOT ALLOW THE EXCLUSION OR LIMITA-TION OF LIABILITY FOR CONSEQUENTIAL, SPECIAL, INDIRECT,INCIDENTAL DAMAGES AND, ACCORDINGLY, SOME PORTIONSOF THESE LIMITATIONS MAY NOT APPLY TO YOU. BY YOUROPENING OF THIS SEALED PACKAGE OR INSTALLING ORUSING THE SOFTWARE, YOU HAVE ACCEPTED THAT THEABOVE LIMITATIONS OR THE MAXIMUM LEGALLY APPLICA-BLE SUBSET OF THESE LIMITATIONS APPLY TO YOUR PUR-CHASE OF THIS SOFTWARE.'

Printing History

January 2009

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C O N T E N T S

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MIKE BASIN User’s Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.1 About MIKE BASIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.2 About this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111.3 Adding and Removing the MIKE BASIN Extension from ArcMap . . . . . 12

2 MIKE BASIN OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132.1 The Graphical User Interface . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.1.1 The Toolbars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162.1.2 Overview of MIKE BASIN drop-down menu . . . . . . . . . . . . 182.1.3 Property dialogs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.2 Quick overview of MIKE BASIN building blocks . . . . . . . . . . . . . . . 232.2.1 Rivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.2.2 Catchments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.2.3 Water Users . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242.2.4 Reservoirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252.2.5 Hydropower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.3 Starting up MIKE BASIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262.3.1 Illustrating how to create a simple model . . . . . . . . . . . . . . 27

2.4 Running a MIKE BASIN Simulation . . . . . . . . . . . . . . . . . . . . . . 302.5 Result Presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.5.1 MIKE BASIN Result Groups . . . . . . . . . . . . . . . . . . . . . 32

3 TIME SERIES IN MIKE BASIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.1 The Engineering Unit Managenemt (EUM) System . . . . . . . . . . . . 353.2 Time series recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373.3 Constant values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373.4 Adding time series to MIKE BASIN . . . . . . . . . . . . . . . . . . . . . . 383.5 Item type editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.6 Table editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.6.1 Copy / Paste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.6.2 Importing time series . . . . . . . . . . . . . . . . . . . . . . . . . 40

4 RULES IN MIKE BASIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5 RIVER NETWORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455.1 Creating a river network . . . . . . . . . . . . . . . . . . . . . . . . . . . . 455.2 General River Reach Properties . . . . . . . . . . . . . . . . . . . . . . . 47

5.2.1 Flow losses (optional) . . . . . . . . . . . . . . . . . . . . . . . . 485.2.2 Flow capacity time series (optional) . . . . . . . . . . . . . . . . . 49

5.3 River Hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 495.3.1 No routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 505.3.2 Linear reservoir routing . . . . . . . . . . . . . . . . . . . . . . . . 50

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5.3.3 Muskingum Routing . . . . . . . . . . . . . . . . . . . . . . . . . . 515.3.4 Wave Translation . . . . . . . . . . . . . . . . . . . . . . . . . . . 535.3.5 Water level calculation . . . . . . . . . . . . . . . . . . . . . . . . 535.3.6 Rating curve approach . . . . . . . . . . . . . . . . . . . . . . . . 545.3.7 Manning formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545.3.8 Head Loss (Hydropower) . . . . . . . . . . . . . . . . . . . . . . . 55

5.4 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

6 RIVER NODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 596.1 Simple Node Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

6.1.1 Priority of Downstream Demand . . . . . . . . . . . . . . . . . . . 606.1.2 Minimum Flow Rule . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.2 Bifurcation Node properties . . . . . . . . . . . . . . . . . . . . . . . . . . 63

7 CATCHMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657.1 Schematic Catchments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 657.2 Delineated catchments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

7.2.1 Importing catchment shapes . . . . . . . . . . . . . . . . . . . . . 667.2.2 Delineating catchments . . . . . . . . . . . . . . . . . . . . . . . . 67

7.3 General catchment properties . . . . . . . . . . . . . . . . . . . . . . . . . 717.4 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

7.4.1 Linear Reservoir model . . . . . . . . . . . . . . . . . . . . . . . . 737.4.2 Groundwater Model Tab . . . . . . . . . . . . . . . . . . . . . . . 74

7.5 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 767.5.1 WQ in Groundwater tab . . . . . . . . . . . . . . . . . . . . . . . 77

8 WATER USER NODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 798.1 General Water User Properties . . . . . . . . . . . . . . . . . . . . . . . . 808.2 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848.3 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

9 RESERVOIRS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 879.1 General Reservoir Properties . . . . . . . . . . . . . . . . . . . . . . . . . 889.2 Rule Curves Reservoirs and Lakes . . . . . . . . . . . . . . . . . . . . . . 919.3 Rules specifically for Allocation Pool reservoirs . . . . . . . . . . . . . . 1019.4 Spillways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049.5 Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

10 HYDROPOWER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10910.1 Hydropower - Formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

11 IRRIGATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11311.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11311.2 Node and sub-model relationship . . . . . . . . . . . . . . . . . . . . . . 114

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11.2.1 Editing sub-model menus . . . . . . . . . . . . . . . . . . . . . . 11511.3 The Irrigation Node . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

11.3.1 Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11611.3.2 Surface Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11911.3.3 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

11.4 Sub-Model Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12011.4.1 The Climate Sub-Model . . . . . . . . . . . . . . . . . . . . . . . 12011.4.2 Reference Evapotranspiration . . . . . . . . . . . . . . . . . . . . 12111.4.3 Soil Water Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 12211.4.4 Irrigation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12311.4.5 Crop Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12411.4.6 Yield Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12611.4.7 Crop Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

11.5 Simulation output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

12 FEATURE SYMBOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12912.1 The Classic Symbology option (default) . . . . . . . . . . . . . . . . . . . 12912.2 The Advanced Symbology option . . . . . . . . . . . . . . . . . . . . . . . 130

13 RESULT PRESENTATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13313.1 MIKE BASIN Result Presentation Wizard . . . . . . . . . . . . . . . . . . 13513.2 Result Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14013.3 Animated maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

14 MACRO PROGRAMMING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14314.1 Overview of interfaces and enumerations . . . . . . . . . . . . . . . . . . 14414.2 Macro Assistant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14414.3 Adding references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14614.4 Editing the Macro . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146

15 OPTIMIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14915.1 Theoretical background (brief) . . . . . . . . . . . . . . . . . . . . . . . . 149

15.1.1 Lack of sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . 15115.1.2 Local vs global optima . . . . . . . . . . . . . . . . . . . . . . . . 15115.1.3 Ill-defined problems . . . . . . . . . . . . . . . . . . . . . . . . . . 15215.1.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

15.2 Working with Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . 15215.2.1 Optimization Problem Dialog . . . . . . . . . . . . . . . . . . . . 15315.2.2 Run MIKE BASIN dialog - Optimization . . . . . . . . . . . . . . 15615.2.3 Options Dialog (Advanced tab) - Numerical Settings . . . . . . . 157

15.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

16 WATER QUALITY MODELING . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15916.1 Modeled Substances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

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16.2 Processes: Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16016.3 Rates: Temperature Dependency . . . . . . . . . . . . . . . . . . . . . . 16216.4 Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16216.5 Within-Catchment Decay for Non-Point Sources . . . . . . . . . . . . . 16316.6 Reservoirs: Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 16416.7 Groundwater: Water Quality . . . . . . . . . . . . . . . . . . . . . . . . . 16516.8 Re-aeration from Weirs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

17 LOAD CALCULATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16917.1 Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

17.1.1 Shape file attributes . . . . . . . . . . . . . . . . . . . . . . . . . 17017.1.2 Time distribution (alpha time series) . . . . . . . . . . . . . . . 17117.1.3 Runoff Coefficients button . . . . . . . . . . . . . . . . . . . . . 17117.1.4 Source Editors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17217.1.5 Runoff Coefficients Editor . . . . . . . . . . . . . . . . . . . . . 17517.1.6 Load Reduction Factors Editor . . . . . . . . . . . . . . . . . . . 17717.1.7 Load Sources Table . . . . . . . . . . . . . . . . . . . . . . . . 17717.1.8 Load Source Fluxes Editor . . . . . . . . . . . . . . . . . . . . . 17717.1.9 Treatment Efficiencies Editor . . . . . . . . . . . . . . . . . . . 178

17.2 Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17917.2.1 General Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17917.2.2 Distance Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . 18017.2.3 MIKE 11 Links . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18217.2.4 Transport Editors . . . . . . . . . . . . . . . . . . . . . . . . . . 187

17.3 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19117.3.1 .Maps and Statistics output . . . . . . . . . . . . . . . . . . . . . 19117.3.2 MIKE BASIN output . . . . . . . . . . . . . . . . . . . . . . . . . 19317.3.3 MIKE 11 output . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

18 NAM RAINFALL-RUNOFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19518.1 NAM Overview Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

18.1.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19618.2 Run NAM Simulation Button . . . . . . . . . . . . . . . . . . . . . . . . . 19918.3 Select TS Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19918.4 TS Weights Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20018.5 NAM Surface-Rootzone Tab . . . . . . . . . . . . . . . . . . . . . . . . . 201

18.5.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20118.6 Ground Water Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

18.6.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20218.7 Snow Melt Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

18.7.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20418.8 Elevation Zones Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

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18.8.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20418.9 Initial Conditions Tab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205

18.9.1 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20618.10 Rainfall Runoff Step-by-Step (for MIKE BASIN) . . . . . . . . . . . . . . 206

19 NAM RAINFALL-RUNOFF TECHNICAL REFERENCE . . . . . . . . . . . . . . 21119.1 NAM - Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21119.2 Data Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

19.2.1 Meteorological data . . . . . . . . . . . . . . . . . . . . . . . . . . 21219.2.2 Hydrological data . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

19.3 Model Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21419.4 Basic modelling components . . . . . . . . . . . . . . . . . . . . . . . . . 21619.5 Extended groundwater components . . . . . . . . . . . . . . . . . . . . . 21819.6 Snow module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220

19.6.1 Altitude-distributed snowmelt model . . . . . . . . . . . . . . . . 22119.6.2 Adjustment of temperature and precipitation to altitude zones . 22319.6.3 Extended components . . . . . . . . . . . . . . . . . . . . . . . . 225

19.7 Model parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22519.7.1 Surface and root zone parameters . . . . . . . . . . . . . . . . . 22619.7.2 Groundwater parameters . . . . . . . . . . . . . . . . . . . . . . . 22919.7.3 Snow module parameters . . . . . . . . . . . . . . . . . . . . . . 231

19.8 Initial conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23219.9 Model calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232

19.9.1 Calibration objectives and evaluation measures . . . . . . . . . 23219.9.2 Manual calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . 234

19.10 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235

Interface Programming Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239

20 FOR VISUAL BASIC MACRO PROGRAMMING . . . . . . . . . . . . . . . . . . 24120.1 Overview of interfaces and enumerations . . . . . . . . . . . . . . . . . . 24120.2 Some tips and tricks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241

20.2.1 Call by reference . . . . . . . . . . . . . . . . . . . . . . . . . . . 24120.2.2 Call by value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24220.2.3 Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24220.2.4 Option Explicit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24320.2.5 Static vs dim . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24320.2.6 Daisy-chaining vs temporary variables . . . . . . . . . . . . . . . 244

20.3 DHI_MIKEBASIN_Engine.Engine interface methods . . . . . . . . . . . 24520.3.1 Initialize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24520.3.2 Simulate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24520.3.3 Optimize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

6 MIKE BASIN

20.3.4 RunAll . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24520.3.5 SimulateTimeStep . . . . . . . . . . . . . . . . . . . . . . . . . . 24620.3.6 AdvanceTimeStep . . . . . . . . . . . . . . . . . . . . . . . . . . 24620.3.7 RememberForHotstart . . . . . . . . . . . . . . . . . . . . . . . 24620.3.8 GetModelObject . . . . . . . . . . . . . . . . . . . . . . . . . . . 24720.3.9 GetIthRuleForNode . . . . . . . . . . . . . . . . . . . . . . . . . 247

20.4 Lesser used DHI_MIKEBASIN_Engine.Engine methods . . . . . . . . . 24720.4.1 SetSimulationOptions . . . . . . . . . . . . . . . . . . . . . . . . 24820.4.2 SetSimulationTiming . . . . . . . . . . . . . . . . . . . . . . . . 24820.4.3 SetInputTimeSeriesValue . . . . . . . . . . . . . . . . . . . . . 24820.4.4 GetCurrTimeStepInfo . . . . . . . . . . . . . . . . . . . . . . . . 24920.4.5 ShowStatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24920.4.6 ShowAnyWarnings . . . . . . . . . . . . . . . . . . . . . . . . . 24920.4.7 FinishSimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . 25020.4.8 GetResultsTSObject . . . . . . . . . . . . . . . . . . . . . . . . 25020.4.9 GetTemplateModelObject . . . . . . . . . . . . . . . . . . . . . 25020.4.10 PreInitialize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25020.4.11 Initialize2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25020.4.12 Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25120.4.13 FindModelObject . . . . . . . . . . . . . . . . . . . . . . . . . . . 25120.4.14 GetRulesForNode . . . . . . . . . . . . . . . . . . . . . . . . . . 25120.4.15 RestoreFromHotstartFile . . . . . . . . . . . . . . . . . . . . . . 251

20.5 DHI_MIKEBASIN_Engine.Engine interface properties . . . . . . . . . . 25220.5.1 Initialized . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25220.5.2 WorkingDirectory . . . . . . . . . . . . . . . . . . . . . . . . . . 25220.5.3 WriteOutput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25220.5.4 NumberOfNetworkElements . . . . . . . . . . . . . . . . . . . . 25220.5.5 NumberOfObjects . . . . . . . . . . . . . . . . . . . . . . . . . . 25220.5.6 SimulationStart . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25220.5.7 SimulationEnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25220.5.8 TimeOfForecast . . . . . . . . . . . . . . . . . . . . . . . . . . . 25320.5.9 TimeStep . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25320.5.10 StochasticPeriod . . . . . . . . . . . . . . . . . . . . . . . . . . . 25320.5.11 NumberOfTimeSteps . . . . . . . . . . . . . . . . . . . . . . . . 25320.5.12 Silent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25320.5.13 OptimizationMode . . . . . . . . . . . . . . . . . . . . . . . . . . 25320.5.14 SimulationDescription . . . . . . . . . . . . . . . . . . . . . . . . 253

20.6 DHI_MIKEBASIN_Engine.ModelObject interface methods . . . . . . . 25420.6.1 GetBasicInfo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25420.6.2 FindResultIndex . . . . . . . . . . . . . . . . . . . . . . . . . . . 25420.6.3 GetCurrentResult . . . . . . . . . . . . . . . . . . . . . . . . . . 25420.6.4 GetAverageResult . . . . . . . . . . . . . . . . . . . . . . . . . . 25520.6.5 FindInputIndex . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25520.6.6 GetInputSpecs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

7

20.6.7 GetInputOriginalValue . . . . . . . . . . . . . . . . . . . . . . . . 25620.6.8 SetInput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256

20.7 Lesser used DHI_MIKEBASIN_Engine.ModelObject methods . . . . . . 25720.7.1 GetExtendedInfo . . . . . . . . . . . . . . . . . . . . . . . . . . . 25720.7.2 GetResultSpecs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25720.7.3 GetDayResult . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25820.7.4 GetMonthResult . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25820.7.5 GetInputTSObject . . . . . . . . . . . . . . . . . . . . . . . . . . . 25820.7.6 GetOverwriteableVariableSpecs . . . . . . . . . . . . . . . . . . 25820.7.7 OverwriteVariableInComingTimeStep . . . . . . . . . . . . . . . 258

20.8 DHI_MikeBasin_Data enumerations . . . . . . . . . . . . . . . . . . . . . 25820.8.1 ObjectTypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25820.8.2 WqSimulationModes . . . . . . . . . . . . . . . . . . . . . . . . . 25920.8.3 OptimizationModes . . . . . . . . . . . . . . . . . . . . . . . . . . 25920.8.4 RuleTypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259

21 MIKE BASIN DATA MODEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26121.1 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26121.2 Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26221.3 Topology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26221.4 Physical Values (Units) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26421.5 Time series and XY-type lookup tables . . . . . . . . . . . . . . . . . . . 264

8 MIKE BASIN

M I K E B A S I NUser’s Guide

9

10 MIKE BASIN

About MIKE BASIN

1 INTRODUCTION

1.1 About MIKE BASIN

The rationale of undertaking water resources studies on a basin scale instead of on a project by project basis is based on the recognition that the water and land resources of a basin forms a unity and hence must be treated as such if future conflicts over water utilization are to be avoided.

For addressing water allocation, conjunctive water use, reservoir opera-tion, or water quality issues, MIKE BASIN couples the power of ArcGIS with comprehensive hydrologic modelling to provide basin-scale solu-tions. The MIKE BASIN philosophy is to keep modelling simple and intu-itive, yet provide in-depth insight for planning and management.

Being an ArcGIS extension, MIKE BASIN allows for some integration between model input/output and existing GIS data. Moreover, MIKE BASIN embeds another DHI GIS Extension, Temporal Analyst, which implies that an abundance of tools for spatial associations, analysis and presentation of time series data are available.

Moreover, the MIKE BASIN code is open-ended, and through the exten-sive COM/.NET interface all input, output and allocation rules can be accessed and manipulated, allowing for extensive customization and even allowing for full integration of MIKE BASIN in external modelling sys-tems. Examples are economic or ecologic models, customized pre- and postprocessors and tailor made decision support systems.

1.2 About this Manual

The MIKE BASIN includes the full documentation as part of the on-line help system, which can be accessed from the MIKE BASIN toolbar. By pressing the F1 key in the dialogs, the documentation is also accessed. The online help for Temporal Analyst can be accessed from the Temporal Ana-lyst toolbar.

The purpose of the overview section, ref. MIKE BASIN overview (p. 13) is to provide just enough information for the user to get started. It is also recommended to read the time series section , ref. Time series in MIKE BASIN (p. 35) before you start setting up a model.

Additional resources are continually updated on the MIKE BASIN web site, www.mikebasin.com.

MIKE BASIN User’s Guide 11

Introduction

1.3 Adding and Removing the MIKE BASIN Extension from ArcMap

MIKE BASIN is an ArcGIS extension and can be added and removed from the ArcMap document like any other ArcGIS extension. When you remove the MIKE BASIN extension, the tools in the MIKE BASIN tool-bar will be disabled. To disable/enable the MIKE BASIN extensions fol-low the steps below:

1 From the ArcGIS menu, select “Tools”, and click on “Extensions”

2 In the Extensions dialog, check or uncheck the MIKE BASIN exten-sion. Important: The Temporal Analyst Extension has to be enabled before the MIKE BASIN extension can be enabled.

3 Click Close.

To remove or add the MIKE BASIN toolbar, follow the steps below:

1 From the ArcGIS menu, select “Tools”, and click on “Customize”.

2 Check or uncheck MIKE BASIN in the list under the Toolbars tab.

3 Click Close.

Notice: The MIKE BASIN toolbar may be disabled even though the MIKE BASIN extension is enabled and visa versa.

12 MIKE BASIN

2 MIKE BASIN OVERVIEWMIKE BASIN is a powerful multi-purpose modelling package for profes-sionals working with water resources projects.

At first glance MIKE BASIN gives the impression of being "just" a simu-lation package for river basin water allocation investigations. But it pro-vides functionalities within a GIS environment for many kinds of investigations.

The philosophy behind MIKE BASIN is to be a simple, intuitive and easy-to-use "office" package, which serves the analysis needs, large or small, forof water resources practitioners. The main areas of work, which MIKE BASIN supports are:

Water allocation scenario modelling;

Reservoir/hydropower operation;

Hydrological modelling;

Irrigation demand and yield assessment;

In-stream nutrient modelling;

Catchment nutrient load assessment;

Time series data management and analysis.

For river basin modelling analysis, either on basin scale or project scale, MIKE BASIN operates on the basis of a schematic river network, which can either be digitized on the screen, based on an imported shape file or traced from a digital elevation model. Besides rivers (referred to as reaches or branches), other buidling blocks which constitues a MIKE BASIN model are:

Water User nodes;

Irrigation usage nodes;

Hydrological Catchment polygons;

Reservoirs nodes (Lakes, Rule Curve Reservoirs, Allocation Pool res-ervoirs);

Hydropower Plant nodes;

Link channel lines.

The behavior of the individual building blocks as well as the interactions between them are defined using the built-in operation rules, or through creation of customized rules in a macro program, which can access the

13

MIKE BASIN overview

MIKE BASIN egine through its COM interface. A built-in Macro Assist-ant helps the user to create the skeleton macro, on which the customization is based.

All information regarding the configuration and the linkages between the model building blocks are defined through on-screen editing in ArcMap. Catchment boundaries are schematically represented by a given shape of a ploygon. Catchment polygons can also be imported from existing GIS lay-ers, delineated using a digital elevation model, or modified on the screen, see Catchments (p. 65).

The computational engine of MIKE BASIN solves the flow between each node/branch according to the input data and stores the stationary solution for each time step. The simulation time step can be any positive time span ranging from seconds to months. The time step of input data can be differ-ent from the simulation time step, and may even vary throughout a time series.

MIKE BASIN may be used together with optimization algorithms. The concept for optimization is its generality, and MIKE BASIN can optimize with respect to any objective.

With the WQ module, MIKE BASIN can simulate steady-state reactive transport of the most important nutrient substances affecting water quality. Point sources as well as non-point pollution can be modeled, and the Load Calculator (p. 169), which is part of MIKE BASIN WQ, allows easy inte-gration of other GIS-based data for automatic calculation of the non-point nutrient loads from catchment areas. Certain point sources are included in the Load Calculator as well.

Runoff from individual catchments can either be specified as time series or computed using a hydrological modelling, see NAM Rainfall-Runoff (p. 195).

Finally, the simulation results can be easily viewed by simple rigth click on the node, branch or catchment of interest. Visualization as animations or overlays can be created, and time series results can be analyzed using the tools collection from another ArcGIS Extension, DHI’s Temporal Analyst, which is fully embedded in MIKE BASIN.

2.1 The Graphical User Interface

The MIKE BASIN graphical user interface (GUI) is empowered by ESRI’s ArcMAP. When MIKE BASIN is started up, an ArcMAP project

14 MIKE BASIN

The Graphical User Interface

file (*.mxd) and a geodatabase file (*.mdb) are created. The layout of the user interface is presented in Figure 2.1.

The central part of the GUI is the Model View, in which all models are created. The model view can be seen as a dashboard, where objects (build-ing blocks, layers etc) can be placed. The model can be geo-referenced, which is particular useful if a model is displayed together with other GIS information. The easiest way to make a model geo-referenced is to add a georeferenced layer or image before starting to build a model.

All MIKE BASIN functionality for setting up a model and running a model is available from a single toolbar, called MIKE BASIN, that appears in the ArcMAP user interface when MIKE BASIN is installed. Extra tool-bars are available for advanced result presentation, MIKE BASIN Results, for time series analysis, Temporal Analyst.

The model building blocks and editing tools are available from the MIKE BASIN Toolbar. Other tools and utilities are available from the MIKE BASIN drop-down menu at the left hand-side of the toolbar as shown in Figure 2.2.

Figure 2.1 The MIKE BASIN User Interface in ArcMAP.

15

MIKE BASIN overview

In addition, the conventional ArcMAP toolbars are available for MIKE BASIN applications.

Besides the specific toolbars for MIKE BASIN, the interface also differs from the conventional ArcMap by having a Time Series tap at the bottom of the Table of Content view. This allows you to access time series data directly from the Table of Content as well as accessing different time series functionalities and analysis tools.

A dockable window, the Time series Analysis window, appears whenever a time series is being viewed or edited. Multiple time series can be viewed under same or different taps that are created as more time series are viewed or edited. This Time series Analysis window is also home for the analysis tools in Temporal Analyst.

2.1.1 The ToolbarsThe MIKE BASIN Toolbar is divided into different parts:

Part1: Start/Stop Editing.

Clicking on these tools will either start or end the edit mode. The map will automatically be in edit mode when you click on a building block tool. Editing mode will be terminated with a reminder to save the edits when the Stop Editing tool or other tools that are not used for creating or modi-fying the model network (not Part 3 tools) are selected.

Part2: River Trace/Catchment delineate tools.

These tools are used when a Digital Elevation Model is available and added to the ArcMAP project for river tracing and catchment delineation. This is explained in Delineating catchments (p. 67).

Part3: Model building tools.

The individual objects of a building block are added to the model by click-ing on the relevant tool in Part 3. The object is then inserted in the model view when clicked at a location in the view.

Part4: Properties tool.

This tool is selected (notice: the cursor changes shape) for specifying attribute data, which describes the property of the individual object of a building block. The property dialog is accessed by clicking on the object.

Part5: Run MIKE BASIN Simulation.

16 MIKE BASIN


This tool is selected when the created model needs to be run, see Running a MIKE BASIN Simulation (p. 30)

Part 6: Results Group Definitions.

This tool opens a dialog for specifying the variables to be stored for result presentation, see MIKE BASIN Result Groups (p. 32).

Part 7: Drop down menu.

This part is described in detailed in Overview of MIKE BASIN drop-down menu (p. 18) Section below.

Part 8: MIKE BASIN Results.

This toolbar contains several tools which assist you in creating result pres-entation in the form of tables, graphs and animations. This is described in detail in Result presentation (p. 133).

Figure 2.2 The MIKE BASIN Toolbar and drop-down menu.

17

MIKE BASIN overview

2.1.2 Overview of MIKE BASIN drop-down menu

New/Open Project... Opens the window to create a new project or opening an existing project

Figure 2.3 New/open dialog

Options...MIKE BASIN options can be changed here. The dialog will automatically appear when you start a new project with a new database.

Under the General tab, you can select additional modelling functionality, e.g. Water quality and Groundwater.

Notice, that once the unit system has been selected in connection with a new project, it can no longer be changed. The unit system selection is use-ful, becaue it determines the default units of the time series templates, which appear when you click on the “New...” button to open a new time series. However, units can allways be changed when editing time series files.

18 MIKE BASIN


Figure 2.4 MIKE BASIN Options General tab

In Advanced tab, you can change numerical settings for simulation.

The old method can be used by ticking Add minimum release from reser-voirs to total hydropower demand. More information is described in Hydropower (p. 109).

Figure 2.5 MIKE BASIN Options Advanced tab

In symbology tab, you can switch Classic Symbology and Advanced sym-bology. See more information about symbology in Feature Symbology (p. 129)

19

MIKE BASIN overview

Figure 2.6 MIKE BASIN Symbology tab.

MIKE BASIN AttributesThe the attributes of the individual building blocks can conveniently be specified in a tabular form instead of the properties dialogs if there are many objects of the same type of building blocks in the model setup. This will allow you to edit several objects in a table and utilize e.g. copy/paste functionality. Figure 2.7shows the table for the reservoir building blocks.

Figure 2.7 Example of the attribute table. Notice that the attribute table will appear in the same dockable window e.g. the time series.

20 MIKE BASIN


Copy Branch Shapes....Shapes files of branches, which has been added to the project can be imported and used in the MIKE BASIN network.

Copy Catchment Shapes....Shape files of catchments polygons can be used as catchment building block objects. In the dialog individual cathments can be associated to spe-cific branches.

Process DEM...This gives you access to a dialog where you can utilize a Digital Elevation Model raster grid for tracing rivers and delineate catchments. In this dia-log you can also use river and basin shapes for creating a pseudo DEM, which can be used for an approximative catchment delineation in which the catchment boundaries are defined as the geometric midpoint between adjacent rivers. This is further described in Section: Delineating catch-ments (p. 67)

DiagnosticsThis menu item helps you to trace and repair possible errors in the model setup thorugh the following tools:

Check model input. All the property menues are reviewed and missing data are noticed;

Clean up and repair database. The data base is reviewed and repaired in case wrong links or connections are occuring in the geodatabase;

Reload project.

Macro Assistant....The Macro Assistant is a convenient tool for creating macros in VB. It reviews the model setup and allow you to select the variable needed to be defined and used in the macro. This concerns both input variables as well as results. This is further decribed in Macro programming (p. 143)

Optimization Problem....This gives you access to a Optimization Problem Definiton dialog, which similar to the Macro Assistant dialog helps you to access the variables to be optimized and the Object Function Terms.

Notice: that the in-built optimization in MIKE BASIN only allows you limited optimization opportunities.

21

MIKE BASIN overview

Irrigation dataThis menu provides access to all dialogs required for developing irrigation demand models for irrigation usage nodes. The irrigation model will cal-culate irrigation demands based on climate, soil, crop and management information. Options for calculating irrigation yields based on water avail-ability is also available, ref. Irrigation (p. 113).

Rainfall RunoffThis gives you access to the hydrological model in MIKE BASIN, ref. NAM Rainfall-Runoff (p. 195)

Load CalculatorThis gives you access to the Load Calculator for catchment load calcula-tions. Notice this is only access if the Load Calculator extension is enabled in the ArcGIS extensions dialog (ArcGIS Tools->Extensions...).

Documentation...An electronic version of the MIKE BASIN manual can be opened from this menu.

MIKE BASIN Web Site...This refers you to the MIKE BASIN Web Site, if you are online.

2.1.3 Property dialogsWhen an object of a building block has been added to the model view, the attributes are specified by clicking on the object, using the cursor that appears after clicking on the MB features properties button (part 4) or by right-clicking and selecting “MIKE BASIN Properties”. An example of a property dialog is shown in Figure 2.8 (Water User).

A brief introduction to each of the building blocks are provided below, see Quick overview of MIKE BASIN building blocks (p. 23). A more com-prehensive description is given in later Chapters.

Even though the properties dialogs for the individual building blocks are different, they share a number of common editing options. The common editing options are marked in Figure 2.8 (part 1, 2, and 3).

22 MIKE BASIN

Quick overview of MIKE BASIN building blocks

Figure 2.8 The Water User Property dialog.

Part 1 is common for all dialogs, and it may be used to name the object, and optionally to provide a category. Classifying a building block in dif-ferent categories may be important in connection with presenting model results and enhance the visualisation of the model setup.

Part 2 is the common time series selection editing option. By moving the cursor over the Use filter area, you can see the valid options for each time series. By clicking on the “New...” button, a default timeseries file will be created. The default time series can subsequently be modified.

The editing sections in Part 3 are examples of the common editing option for specification of allocation rules, return flow options etc.

2.2 Quick overview of MIKE BASIN building blocks

2.2.1 RiversRivers are added to the model by: 1) importing it from an existing GIS layer; or 2) traced from an elevation model using the MIKE BASIN River Tracing tool; or 3) by manually digitizing the rivers on a map background.

23

MIKE BASIN overview

If required, three different routing options are available (Wave translation, Linear routing, and Muskingum routing). Seepage and flow losses may be included and for pipes and closed channel sections a time dependent flow capacity can be specified.

2.2.2 CatchmentsA model can include any number of hydrological catchments. Catchments are added to the setup by 1) importing the appropriate shapes from an existing GIS map; or 2) by using one of the tools for delimiting the catch-ments directly from an elevation model. Catchments may also be repre-sented schematically by 3) adding a catchment node on the river network.

Optionally, groundwater processes can be included in the runoff descrip-tion of a catchment. The underlying conceptual hydraulic model is the lin-ear reservoir model with one or two aquifers (fast/slow response). Recharge to the groundwater has to be provided by the user, either as spe-cific or absolute recharge.

Groundwater interacts with the surface water via groundwater recharge, groundwater discharge and stream seepage, and can be pumped by the water users in the area, allowing for studies of conjunctive use of surface- and groundwater.

MIKE BASIN comes with a rainfall-runoff model (NAM). If the existing flow records need gapfilling or extension, NAM can be used to calculate runoff based on time series of rainfall and potential evapotranspiration. NAM is a lumped, conceptual rainfall-runoff model simulating flow as a function of the moisture content in each of four interconnected storages.

2.2.3 Water UsersA Water User node, including Irrigation User nodesThe building blocks are added to the model by clicking a button in part 3 of the toolbar and the selected building block is inserted when a point in the model view is clicked., represents any user that abstracts, consumes and returns surface and/or groundwater. Examples are municipal or industrial water supply. Water demands are specified as time series, and water can be abstracted from river nodes, reservoirs or groundwater. Each user can have multiple sources, and a single source can provide water for multiple users. Return flow can be to any number of nodes along the river, or re-infiltrated to the groundwater.

In situations of water shortage, conflicts about the distribution of water will occur. For surface water, a strict priority ("riparian rights") or a shared priority ("fractional allocation"), or any combination thereof, can be enforced. With strict priority, given a node with several users, the user

24 MIKE BASIN

Quick overview of MIKE BASIN building blocks

with the highest local priority receives its entire demand (if available) before the second node is considered. This second node receives its demand from the remainder volume (i.e., after the first node has received its water), and so on for the subsequent nodes.

With shared priority, a group of users each receive a predefined share of the available water.

2.2.4 Reservoirs

MIKE BASIN has extensive reservoir modelling capabilities, and can accommodate everything from simple lakes to complex multi-purpose interconnected reservoir systems. MIKE BASIN has three different types of reservoirs:

Lakes

Rule Curve Reservoirs

Allocation pool reservoirs.

All reservoir types are characterized by a geometry (Level, area, volume relationship) and a spillway relation that defines the level and optionally the Q-h relation for the spillways. Losses and gains represented by precip-itation, seepage and evaporation may also be included.

Lakes are the simplest reservoir type, and besides the options described above, lakes are not operated.

The Rule curve reservoir has a common physical storage that all con-nected users are drawing water from. Operation rules for each user apply to the same storage. This mode of operation generally requires that a water user is curtailed according to different reservoir levels. These levels can vary throughout the year and the user will be curtailed when the water level is within the zones defined by the rule curves. Different sets of rule curves may apply to different users.

Rule curve reservoirs can also be operated such as to maintain certain minimum (environmental) or maximum flows at some far downstream control locations, and MIKE BASIN allows calculation of the mandatory releases as a function of time. Releases through a bottom outlet (with a limiting capacity) can also be modelled.

As an alternative to the rule curve reservoir, MIKE BASIN has the Allo-cation Pool Reservoir. The allocation pool reservoir implements the Water Banking system, also referred to as the Fractional Water Allocation and Capacity Sharing (FWA-CS) system. For Allocation pool reservoirs,

25

MIKE BASIN overview

the storage is divided into storages, and entitlements are issued according to these storages.

From an operational point of view, water users will operate their share of dam capacity like a bank account. Inflows will increase the account, whereas releases, pro-rata evaporation and pro-rata seepage losses will be deducted from their account. The account can be operated on a relevant time step, e.g. weekly, forth-nightly or monthly.

Multiple reservoirs can have complicated inter-dependent rule curves. MIKE BASIN can simulate reservoirs in tandem, both bi-directional transfer between neighbouring reservoirs and uni-directional transfer within reservoir cascades.

Realizing that some reservoirs may have even more complex operation rules than what can be modelled with the above facilities, MIKE BASIN offers the possibility to implement new, or modify existing rules through the use of Visual Basic macros. This allows the user to define essentially any operation policy. A built-in macro-assistant helps the user to get started with the macro programming

2.2.5 HydropowerMIKE BASIN has the ability to perform advanced hydropower simulation be it for existing systems or to evaluate the feasibility of new develop-ments. Hydropower is represented in MIKE BASIN as a node that extracts water from one or more reservoirs, produces power according to effective head difference and engine efficiencies, and returns water to one or more downstream locations.

Optionally, conveyance losses, tail water level and backwater effects from cascading reservoirs can be included in the calculations.

series can be analyzed and plotted simply by right-clicking on the individ-ual building blocks and selecting Time Series from the context menu.

2.3 Starting up MIKE BASIN

MIKE BASIN is started up from Windows program manager:

Start ->Programs ->MIKE by DHI 2009 ->MIKE GIS ->MIKE GIS

The start-up window in ArcMAP will prompt you to specify a new map or open an existing map.

26 MIKE BASIN

Starting up MIKE BASIN

Figure 2.9 Start up dialog in ArcMap

If you do not have an existing model, you simply click OK in the dialog and go to the MIKE BASIN Toolbar. In the MIKE BASIN pull-down menu, click on Open/New Project. If you already have an existing project you can select the mxd file in the dialog and click OK, you will then bye-pass the MIKE BASIN Open/New Project dialog, see Figure 2.3.

Once you have selected e.g. a new project with a new database, you are promted for specifying the location of the database. This will be your working directory (workspace) where the project and your data usually also will reside.

You can give the database a name, which relates to your project, by default it will be called ProjectData.mdb.

Once you have specified the name, all the default MIKE BASIN layers will be loaded and appear in the Table of Content. At the same time the MIKE BASIN options dialog will appear, see Figure 2.4.

Once you have closed the options dialog you will be able to start creating a MIKE BASIN model.

2.3.1 Illustrating how to create a simple modelThis example illustrates the steps of creating a simple schematic model as outlined in Figure 2.10 below. This model is created by 14 clicks with the mouse (the numbers refer to the locations in Figure 2.10):

27

MIKE BASIN overview

1: click on Digitize reach/ branch in the toolbar

2: click on a point in the model view for the upstream end of a reach/branch

3: click on a second point in model view

4: doubble click on a point in the model view, where the downstream end of the reach/branch should be located

5: click on a point for the upstream end of the tributary

6: doubble click on connection with first river branch (confluence)

7: click on catchment node in the toolbar

8: click on the confluence node to create two catchments

9: click on Digitize water user in the toolbar

10 click on the location where the water user should appear in the model view

11: click on Add channel in the toolbar

12: click on a point on the river from where to water should be extracted

13: doubble click on the water user node to create the channel

14: click on Stop Editing on the toolbar.

Note, that as long as you are working in Edit mode, you can use the undo bottom. After the structure has been saved and you are no longer in edit mode, and changes to the model structure can only be done through the Edit tool, e.g. by selecting the object and press Delete.

28 MIKE BASIN

Starting up MIKE BASIN

Figure 2.10 A simple model (the numbers refer to the steps above)

The model structure is now finished, and attribute data can be added. The following tasks need to be carried out to have a model that can be exe-cuted.

1: click on MB Feature properties in the toolbar

2: click on one of the catchments, and a dialog appears

2a: disable the tickbox: Use shape area for assigned area

2b: specify an area (e.g. 1000)

2c: click on New...,and select the default time series

2d: click on apply

3: click on the other catchment

3a: repeate 2a and 2b

3b: click on Open..., and select the time series file created in step 2c

3c: click on OK (the dialog will disappear)

29

MIKE BASIN overview

4: click on the water user node and a new dialog appears

4a: click on New...,and select the default time series

4b: click on OK

You are now ready to run the model by clicking on the Run MIKE BASIN simulation... button in the toolbar, see also Running a MIKE BASIN Sim-ulation (p. 30). Notice you can select any simulation period and time step you prefer, the model will run with the input data you have specified, even it does not cover the simulation period.

An example on a more comprehensive model layout is shown in Figure 2.11.

Figure 2.11 Example of a model setup using the advanced symbology option.

2.4 Running a MIKE BASIN Simulation

A MIKE BASIN simulation is executed from the run dialog, see Figure 2.12.

30 MIKE BASIN

Running a MIKE BASIN Simulation

In this dialog the simualtion period can be specified. Notice that MIKE BASIN allows for input time series which has different length than the simulation period, and different temporal resolution than the simulation time step.

If an input time series does not cover the entire simulation period it must cover a period of at least one calender year when the simulation period is longer than a year. If an input time series covers exactly one year it will recycle the time series using the appropriate values for the simulation period, both for the period before and after, for which data exist.

Figure 2.12 MIKE BASIN run dialog

If the input time series is longer than a year, input data from the first full year will be used for the simulation period before data exist, and input data from the last full year will be used for the simulation period after data exists.

Any constant time step can be used in the simulation. Notice that the tem-poral resolution of the input time series can be with any variable temporal resolution different from the simulation time step. Depending on the value type of the time series different interpolation method is used.

It is possible to run MIKE BASIN in a simple stochastic type of mode, where the initial conditions are reset every year. This is convenient if you want to analyse e.g. drought management scenario for a number of months in the future for likely climatic/inflow conditions. Running in the stochas-

31

MIKE BASIN overview

tic mode for say a 20 years period, a 20 years output file of e.g. water level will be produced. It can can be interpretated as the realisation of 20 one years simulations using the same initial condition, but for different inflows and climatic conditions.

Every simulation should be given an ID. Simulation results with an ID already used will overwrite the existing results. All the results from a sim-ulation is stored in a dfs0 time series file with as many items as output var-iables specified.

The output variables to be stored can be specified in a Result Group, which can be defined as described in MIKE BASIN Result Groups (p. 32)

2.5 Result Presentation

All outputs from MIKE BASIN are in the form of time series, which are associated to the building block they represents.

A large number of different plots and statistical tools are available. Among the available plots are duration curves, double-mass curves, within-year statistics and seasonal deviation plots.

For a spatial analysis and overviews, MIKE BASIN includes tools for summarizing input and output time series and presenting the summary sta-tistics as GIS layers. The summary statistics include the simple methods such as minimum, maximum and time-weighed average, but a large number of more advanced tools are available as well. Among the more advance tools are duration quantiles, trend analysis tools, within.period extremes, as well as ramp and event statistics.

Moreover, MIKE BASIN allows you to visualize simulation results as movies, and includes functionality to quantify the difference between two scenarios. MIKE BASIN has a specific toolbar, part 8 in Figure 2.2, for creating maps, graphs and reports.

Finally, the MIKE BASIN Macros can be used in combination with e.g. Microsoft Office to produce result summaries in Excel or Word.

2.5.1 MIKE BASIN Result GroupsUsing MIKE BASIN Result Groups allows you to define exactly the time series that are needed to be stored. If you have chosen <none> (full results) every time series produced will be stored. This will often be useful for small models, but large models with long simulation period and small

32 MIKE BASIN

Result Presentation

time step can create a large quantity of data, which uses large storage space and requires long time to write and subsequently read.

The MIKE BASIN Result Groups tool provides a convenient way of selecting exactly the time series you need to store. It opens a dialog, which has access to all the variables that can be produced in this particular model setup. A name of the result group can be specified and all the relevant var-iables selected. When running the model the name can be selcted in the run dialog.

Figure 2.13 Result Group dialog for defining the time series stored in a simula-tion

33

MIKE BASIN overview

34 MIKE BASIN

The Engineering Unit Managenemt (EUM) System

3 TIME SERIES IN MIKE BASINTime series are the main input to MIKE BASIN, and time series input is required for all MIKE BASIN building blocks. Time series are records with the time stamp in column one, and the data in one or more subse-quent columns called items. Examples of such time series input include Catchment Runoff, Water Demand for the water users, Target Power of the hydropower plants etc.

Creation of new time series, importing esisting time series, as well as the analysis and plotting of time series are generally handled by Temporal Analyst part of MIKE BASIN, and the user is advised to read the docu-mentation of Temporal Analyst in order to get the full benefit of MIKE BASIN. Below is, however, given a brief description of the most impor-tant aspects of time series handling and properties in MIKE BASIN.

3.1 The Engineering Unit Managenemt (EUM) System

Time series used in MIKE BASIN includes four important data property attributes. These attributes are handled by DHI´s so-called Engineering Unit Management (EUM) system. The most important EUM attributes are briefly described below. For a detailed discussion, please consult the Tem-poral Analyst manual.

Property 1: Value TypeThere are two fundamental types of time series in MIKE BASIN: (1) State data (instantaneous) and (2) flux data (reverse mean step accumulated). An example of a state varable is the water level in a reservoir, whereas a rainfall rate is an example of a flux value type.

For a state time series the data value provided for a particular date/time is assumed to be valid at that exact time. The value between two time stamps is determined by linear interpolation.

For flux data the value at a given time stamp is assumed to represent the average value between the given time stamp and the previous time stamp (mean step accumulated) or between the given time stamp and the next time stamp (reverse mean step accumulated).

The plot in Figure 3.1 illustrates the difference between flux data and state data. The plot shows the same data plotted as flux and state data, respec-tively. The time stamps and data values, on which both graphs are based, are shown in the left hand side of the plot.

35

Time series in MIKE BASIN

Figure 3.1 A plot showing the same time series plotted as flux data (full) and state data (dashed). Notice in this example the time series file con-tains two items, of which only the first is shown in the table view.

Notice that the graph for state variables ends one time step before the graph showing the flux variable. The reason is that for state variables, the data value at the last time step (1. December, 2006) represents that partic-ular time only, whereas for the flux values this value represents the time span between 01-12-2006 and the next time stamp (01-01-2007). Hence, for flux data it is important to add a time stamp with no data at the end of the time series to indicate the end of the time span for which the last data value is valid. Otherwise the last data value is assumed valid for all future time.

It is important to undersatnd the principle of value type in connection with manipulation of time series records.

For a detailed discussion of the different time series types available in MIKE BASIN, the user is referred to the Temporal Analyst documenta-tion.

Property 2: Time TypeThe Time Type refers to the type of the time-axis. A time axis can be equi-distant, meaning that the time span between consecutive timesteps is con-stant through the entire time series (e.g. a hourly or daily time step). Alternatively, the time axis can be non-equidistant , implying that the time span between consecutive time stamps are not constant through the entire time series (e.g. a monthly time step).

Property 3: Item TypeThe Item type defines the data type (eg. rainfall, discharge, Water Demand etc.). When time series input is assigned to a MIKE BASIN model, only time series that has a valid Item Type can be added

36 MIKE BASIN

Time series recycling

Example: Only time series that has ItemType “Water Flow” can be used to specify Water Demand for a Water User. Trying to use any other type will result in an error message.

For some inputs more than one ItemType is allowed.

Example: Catchment runoff can be specified as either Discharge or Spe-cific Runoff. If MIKE BASIN detects that the type is Specific Runoff, it will automatically multiply the values in the time series by the catchment area to get the total catchment runoff.

Property 4: Unit TypeFor each variable type, a number of valid units are defined. This ensures that e.g. discharge can not be specified in e.g. square meters, but on the other hands allows the user to choose between a wide range of valid units.

Examples of valid units for e.g. discharge is m3/s and ft3/day, ac-ft/day and many others. MIKE BASIN will automatically detect the used unit and make the necessary conversions.

3.2 Time series recycling

Hydrologic records often do not cover the entire period of time for which a simulation is desired, resulting in a data shortage problem. At the same time, many hydrologic processes are cyclical with a period of one year. Hence, often missing data can be 'borrowed' from equivalent periods in other years for which data are available.

In MIKE BASIN, this otherwise laborious task is performed automati-cally. It is referred to as 'recycling' and requires that the time series con-tains data for at least one full year. If the simulation time is before the start of a time series, data from the first year will be recycled, and if the simula-tion time is after the end of the time series, data from the last year will be recycled.

3.3 Constant values

To represent a constant value in a time series, just add the single constant value with an appropriate time stamp (e.g. 01-01-2006), followed by an additional time step at least one year later (e.g. 01-01-2007) with a blank data value. The value at the forst time stamp will now be recycled for all possible simulation periods.

37


3.4 Adding time series to MIKE BASIN

Most of the features require specification of time series data. These data are always entered in a specific area of the dialogs which has the follow-ing look:

Figure 3.2 The common time series selection dialog (Part 1in Figure 2.8).

Theproperties of the time series selection dialog are described below.:

Click on the New… tool (A) to create a default time series file. Default time series are time series files containing one year of monthly data. Using default time series are very useful as templates for real datafiles, and allows you to get the model running very quicky.

Click on the Open tool (B) to open an existing time series file. Only dfs0 time series files can be opened directly. However, other time series file formats may be used as well (e.g Excel amd ascii formats). Please consult the Temporal Analyst documentation for guidelines on how to import time series.

If a time series has already been included in the model (e.g. if the same time series is to be used for several water users, or if it has already been manually imported into Temporal Analyst), it will already be registred in the MIKE BASIN database. In such cases the desired time series can be selected directly from the pull-down menu (E). If the Use Filter box is checked only files with a valid combination of EUM Variable types are shown in the pull-down menu. Notice, that moving the cursor over the “Use Filter” field will show the valid EUM Variable types for the specific time series.

After having selected a time series file it can be plotted and/or edited by clicking on the Plot/Edit tool (C). For a detailed description of editing of time series, please consult the Temporal Analyst manual.

38 MIKE BASIN

Item type editing

The properties of the time series file can be reviewed by clicking on the properties tool (D).

3.5 Item type editing

As mention above, e.g. for the catchment node, MIKE BASIN can use several Item types for the same node. To change an item to another prop-erty, Item type and corresponding value type or unit type, you can right click in the Part 1 in the time series dock, on the time series name, as shown in Figure 3.3.

Figure 3.3 Item type editing in the time series dock. The timeseries dock con-tains three parts, 1) the item type part; 2) the tabular editing part, and 3) the graphical editing part.

When pointing on the Item Properties.... the following dialog in Figure 3.4 opens.

39


Figure 3.4 Times series property dialog

3.6 Table editing

When you select a new time series a default time series from a template is loaded. After clicking on the Edit/Plot button, Part C in Figure 3.2, the time series dock appears, Figure 3.3, and the table, Part 2, can be edited. After editing the file can be saved, Save Data, or saved as a new file.

3.6.1 Copy / PasteIf you have the data in another format e.g. Excel you can use Copy and Paste to bring data to between the table editor and the Excel. This is a very useful if you do not have too many time series to load into a model.

3.6.2 Importing time seriesIn the Time series collection part of the Table of Content, it is possible to import time series. These time series can be in different formats e.g. Excel, ASCII or others and important through so-called data bridges.

If you choose, eg. the Excel data bridge, you can keep your data en Excel and MIKE BASIN can read the time series directly, provided that th time series are specified with the correct properties.

40 MIKE BASIN

Table editing

Figure 3.5 Import of time series

If you need to import a large number of time series from e.g. Excel, you can use the Time Series Data Loader..., see for additional explanation in the Temporal Analyst Documentation.

41


42 MIKE BASIN

4 RULES IN MIKE BASINAll building blocks, except Catchments can operate according to one or more rules. Examples of available rules are:

– Rules that defines how the water supplied to a water user is restricted as a function of the reservoir level

– Rules that defines how water should be distributed among water users that draws water from the same river node,

– Rules that defines the reservoir release as a function of the river flow at some downstream location.

– and many others...

In the building block properties dialogs rule are often grouped in tables. Each line in the table represents a rule. The properties of the rules are sum-marized in the table (Rule type, time series assiciated with the rule, and an optional comment). Examples of such tables are shown in Figure 4.1 and Figure 2.8 (marked by C).

Figure 4.1 The common MIKE BASIN Rules control.

Adding and editing rules are done by clicking the buttons next to the table (right).

1 Click on the Edit Rule button ( ) to edit in an existing line in the dis-play. You will edit the line with the pointer in the dark blue border area to the right. Alternative you can double click on the pointer. Editing a line will open a new dialog for specification of the items in the line concerned.

2 Click on the Add rule ( ) to create a new rule. A new dialog will for specification of the rule will be opened.

Notice that based on specifications given in other parts of the dialogs or based on the network configurations, the fields may be filled for default conditions. For example, when having specified the reservoir type as a

43

Rules in MIKE BASIN

rule curve reservoir, the Flood control fields under Operation rules will appear for further editing. This also applies e.g. for priority of downstream users for a reservoir.

The specification in the dialogs that appear when clicking on Edit rule or Add Rule are described in the sections for each of the different node types. An example is given in Figure 4.2 that shows a typical Rule definition dia-log for a Reservoir.

Figure 4.2 Rules Editing dialog for a reservoir

Typically, the rule type is selected from the drop-down menu, and often a time series or a table that defines the rule needs to be be specified. If the rule is used to relate a property of the “current” node to a remote node, the remote node is specified as well.

44 MIKE BASIN

Creating a river network

5 RIVER NETWORKRivers networks are made of segments called reaches. Reaches connects, starts and ends in river nodes.

Channels are the segments that connects Water Users and Hydropower nodes to a river or a reservoir. Channels may also be used to connect reser-voirs. The symbology is illustrated in Figure 5.1.

Figure 5.1 MIKE BASIN Reach, Channel and River Node symbology.

Except for the different symbology, reaches and channels share the same properties.

5.1 Creating a river network

River networks can be created in three different ways:

1 Networks can be digitized on-screen.

2 Imported from an existing shapefile

3 Derived from a digital elevation model (DEM)

In either case, it is recommended to reference your network geographi-cally, so that features are located at their correct geographical coordinates. The advantage of doing so is that you can overlay other sources of data to calculate information such as water demand, point and non-point pollution loads, and runoff areas. You will also be able to view results in context of other map data. Georeferencing is, however, not required.

45

River network

Method 1: Digitizing a river networkFor schematic models and small river networks, the network can be digi-tized directly on the screen. An aerial photograph or map is often used as background maps in such situations.

To digitize a river select the Add River Branch tool ( ) from the MIKE BASIN toolbar. Use the left mouse button and click at each point along the river. Always digitize in the direction of flow from the upstream end to the downstream end. To finish the branch, double-click on the last point.

If you make a mistake while you are still digitizing you can type Esc to cancel the operation. If you have alreadyfinished a branch, you can select "Undo" from the Edit menu. You can undo all edit operations back to when you started editing. Once you stop editing however, your edits are committed and saved.

River Nodes will be inserted automatically at beginning and end of a reach, as well as in all confluences and diversions.

Important: Always digitize Rivers and Channels from upstream to down-stream.

Method 2: Importing a river networkThe river network may be imported from an existing shape layer using the “Copy Branch Shapes” tool which is found in the MIKE BASIN drop-down menu.

(CHECK MIKE 11 GIS Documentation)

Method 3: Derive the network from a DEMRiver can be derived automatically from a DEM using the “Trace River” tool which can be found in the MIKE BASIN toolbar ( ).

The tool will, however only be enabled if a processed DEM has been pro-duced with the Process DEM tool which is found in the MIKE BASIN drop-down menu.

Important: The “Process DEM” tool requires ArcGIS Spatial Analyst.

The purpose of the tool is to derive the flow direction from which the riv-ers can be traced. Once the flow direction grid has been produced, the Trace River tool will be enabled.

46 MIKE BASIN

General River Reach Properties

To trace the river from an elevation model, start by adding your elevation model to the project using the “Add data” button in the ArcGIS main tool-bar ( ).

Open the “Process DEM” tool from the MIKE BASIN drop-down menu.

Figure 5.2 The Process DEM Tool.

Select your DEM from the pull-down menu, and press “Calculate Flow Direction”. Depending on the resolution and extent of the selected DEM, this may take several minutes. When the tool finishes, the “Trace River” tool will be enabled in the MIKE BASIN toolbar.

After clicking the Trace River button, rivers can be added to the model simply by clicking at the upstream end of the branch you want to add. The tool will trace the river down to the outlet of the DEM. Subsequent rivers will be traced down to the point where they flow into existing river branches.

Important: Many DEMs contain inaccuracies because of their resolution or artifacts in the method of creation. When delineating catchments and rivers from the DEM, you may find some unexpected results. This can particularly happen in flat areas where DEMs may not have the vertical resolution to correctly delineate the rivers and watersheds.

5.2 General River Reach Properties

Properties are assinged for the individual reaches and channels, implying that different properties can be assigned to different reaches. The proper-ties are accessed by right-clicking on a reach and selecting MIKE BASIN Properties. The properties dialog is shown in Figure 5.3

47

River network

Figure 5.3 River Reach and Channel Properties dialog..

River reaches and Channels has no required attributes. The properties are specified under the three tabs:

General (p. 48)

River Hydraulics (p. 49), and

Water Quality (p. 55)

5.2.1 Flow losses (optional)Rivers and reaches may loose or gain water due to seepage, and loose water to evaporation. If these processes are considered to be of importance the may be included in the model as a time series that specifies the losses/gains. Both seepage and evaporation can be specified as a fraction of the actual flow (dimensionless), or as flux (volume per time).

48 MIKE BASIN

River Hydraulics

When the flow loss factor in a connection channels is different from zero, the water demand (D) of the connected user is automatically adjusted ( D*

) to take the loss into account:

(5.1)

This means the user-specified demands will still be fulfilled if sufficient water is available at the downstream source. This also applies if the con-veyance loss is given as a flux.

When groundwater is defined in the catchment where the reach runs through, the seepage loss from the reach is added to the groundwater.

5.2.2 Flow capacity time series (optional)Reaches and channels may be assigned a flow capacity [Volume per time] that can never be exceeded. The flow capacity overrules all other rules that may try to force more water through the channel.

Example: A water user may call for 5 m3/s. If the flow capacity of the con-necting reach has been set to e.g. 4 m3/s, the user will only recieve max. 4 m3/s and hence suffer a deficit, even though there may be plenty of water at the source.

If the flow capacity of a reach or a channel is reached, the model will attempt to force the water in alternative direction. If this is not possible, the simulation will terminate with a message.

5.3 River Hydraulics

Four different routing options are available under the Hydraulics tab of the properties dialog. The four options are described below.

D* D 1 loss factor–( )⁄=

49

River network

5.3.1 No routingPer default routing is disabled for all reaches.

5.3.2 Linear reservoir routingLinear reservoir routing distributes flow from the upstream node over all time steps following an inflow and extraction to and from the node.

50 MIKE BASIN

River Hydraulics

For a pulse inflow, outflow peaks after a time given by the time lag, and then decays exponentially. The formula used is:

(5.2)

where qo is outflow from the node, dt is time step length, qi is inflow to the node, s is storage in the subsurface, and K is the linear routing time lag (or delay parameter).

Linear reservoir routing can be chosen as a special case of Muskingum routing with x = 0. Unlike general Muskingum routing, linear routing is defined for all combinations of time step lengths and K values.

This algorithm includes damping. For a given time step, reach storage Storage is updated based on the following formula. Variables ∆T and DelayK are as explained previously, and T is an intermediate result.

(5.3)

(5.4)

= (Inflow Volume) - (Outflow Volume); [m3] (5.5)

Note that for linear reservoir routing, reach storage is a virtual quantity that can be negative

5.3.3 Muskingum RoutingSelecting Muskingum routing causes the dialog to change, allowing you to specify two routing parameters.

The K parameter specifies the time for the incremental flood wave to traverse the branch between two nodes. Its value may also be estimated as the observed time of travel of peak flow through the branch. The shape parameter, x (dimensionless) depends on the shape of the modeled wedge storage. In natural rivers, x has a value between >0 and 0.3 with a mean

qo 1 x dt( ) K⁄( )⁄–( ) qi x s with x⋅+⋅ 1 e dt K⁄–( )–= =

T 1.0 e ∆T DelayK( )⁄( ); -[ ]–=

OutflowVolume 1.0 T– ∆T DelayK⁄( )⁄( )InflowVolume T Storage m3[ ]⋅+⋅

=

∆Storage

51

River network

value of 0.2 (always < 0.5). Greater accuracy in determining x may not be necessary because the results are relatively insensitive to the value of this parameter.

The Muskingum method is a commonly used hydrologic routing method for handling a variable discharge-storage relationship. This method mod-els the storage volume of flooding in a river channel by a combination of wedge and prism storage. During the advance of a flood wave, inflow exceeds outflow, producing a wedge of storage. During the recession, out-flow exceeds inflow, resulting in a negative wedge. In addition, there is a prism of storage, which is formed by a volume of constant cross section along the length of the prismatic channel.

Assuming that the cross-sectional area of the flood flow is directly propor-tional to the discharge of the section, the volume of prism storage is equal to KQ, where K is a proportionality coefficient, and the volume of wedge storage is equal to KX(I - Q), where X is a weighting factor having the range. The total storage is therefore the sum of two components.

(5.6)

This expression can be rearranged to give the storage function for the Muskingum method

(5.7)

which represents a linear model for routing flow in streams.

The value of X depends on the shape of the modeled wedge storage. The value of X ranges from 0 for reservoir-type storage to 0.5 for a full wedge. When X = 0, there is no wedge and hence no backwater. In this case, Eq(5.7) results in a linear-reservoir model, S = KQ. The parameter K is the time of travel of the flood wave through the channel reach. K and X are specified and constant throughout the range of flow.

The values of storage at time j and j+1 can be written, respectively, as

(5.8)

(5.9)

S KQ KX I Q–( )+=

S K XI 1 X–( )Q+[ ]=

Sj K XIj 1 X–( )Qj+( )=

Sj 1+ K XIj 1 1 X–( )Qj 1+ + +[ ]=

52 MIKE BASIN

River Hydraulics

Using Eqs. (5.8) and (5.9), the change in storage over time interval is

(5.10)

A comparison between linear reservoir routing and general Muskingum routing is shown below for a case where the latter would be unstable.

5.3.4 Wave Translation

The wave translation algorithm basically uses a cyclical buffer with "slots" for every time step. The inflow at a time step is put into the current, and the corresponding earlier inflow that was stored in that slot is pulled out. The index of the current slot cycles within the buffer, such that a new inflow always replaces the "oldest" previous inflow. The number of slots in the buffer is equal to the number of time steps that a flow gets delayed with. The number of slots is computed as floor (∆T/K), where K can vary among reaches, and ∆T [time] is the simulation time step. The latter must be constant during a simulation; for months, a standard month length (30 days) is assumed.

A good estimate of K can be the travel time of a distinct hydrograph peak between an upstream and a downstream station on the given river.

5.3.5 Water level calculationIn most applications, MIKE BASIN is used to only calculate flows, not water levels. It is not a hydraulic model and thus cannot be used for proper flood modeling. DHI’s MIKE 11 model is more suited for such purposes. However, water level calculations in MIKE BASIN can be useful, particu-larly when simulating water quality.

By default, water levels are not calculated. However, when required. two options are available: the rating curve approach (Q-h table) and the Man-ning's formula. Both apply for steady-state flow and are thus approxima-tions, but usually reasonable as long as the water level does not change rapidly (e.g. during a flood). The items on the dialog change depending on the option chosen.

Sj 1 Sj–+ K XIj 1 1 1 X–( )+( )Qj+ +[ ] XIj 1 X–( )Qj+[ ]–=

53

River network

5.3.6 Rating curve approachWhen the rating curve approach is used, MIKE BASIN looks up the water level in a user specified Q-h table. The table must cover the range of dis-charges encountered during a simulation.

5.3.7 Manning formulaThe Manning formula is

(5.11)

Where n is the Manning number, A is cross-sectional area, S is water sur-face slope, R is the resistance radius:

(5.12)

assuming a rectangular cross-section with width B, and h(b)=h

so R can be written as:

and

(5.13)

Thus water level can be computed as:

(5.14)

You must specify slope and the Manning number. Generally, it is a good approximation to equate surface and channel slope. Optionally, you can also specify a maximum water depth up to which results from the Man-ning formula are accepted. If you specify such a (non-zero) value, water levels will never exceed it.

When selecting the Manning formula approach, the a width B, needs to be specified under the General tap.

Q l n A R 2 3⁄( )⋅ ⋅⁄ S 1 2⁄( )⋅=

R 1 A⁄ h b( ) 3 2⁄( )db( )0

B

∫⋅

2

1 A⁄ h3 2⁄ B⋅ ⋅( )2

= =

1 h⁄ h3 2⁄⋅( )2 as B A⁄= 1 h⁄ h= =

Q l n⁄ h B h 2 3⁄( ) S 1 2⁄( )⋅ ⋅ ⋅ ⋅ l n⁄ h 5 3⁄( ) B S 1 2⁄( )⋅ ⋅ ⋅= =

h Q N⋅( ) B S 1 2⁄( )⋅( )⁄( )3 5⁄( )

=

54 MIKE BASIN

Water Quality

5.3.8 Head Loss (Hydropower)Significant additional head loss in hydropower systems can be caused by friction in the pipes connecting reservoir and turbines. For channels con-necting hydropower nodes to reservoirs, the head loss table section will be enabled in the Reach property dialog. MIKE BASIN uses the following relationship to take head loss into account:

(5.15)

The head loss (∆h) is specified as a function of discharge (Q) in tabular form. Specification of a head loss table is optional, and if no table is pro-vided, head loss will not be taken into consideration.

5.4 Water Quality

In MIKE BASIN, solute decay is modeled to occur in the river reaches, depending on the rate parameters, water volume, and residence time therein.

In the tab, the default choice is to assume conservative transport. When you uncheck that option, you can choose between various methods to specify or calculate residence time.

Residence time intuitively determines the degree of solute decay. Mathe-matically, it is the upper integration limit of the first-order differential equations shown in the Water Quality Modeling (p. 159) section. There are various options to specify or calculate residence time, intended to pro-vide you the highest degree of flexibility for all common types of data available. The options are:

Residence time (and depth): you need to specify a time series group with residence time. This option is convenient if you do not have any other data that allow residence time to be calculated, but have some estimate thereof. Water volume is calculated as the outflow rate times the residence time. If you model DO, you also need to specify water depth and reach length.

∆h k Q2⋅=

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Width and depth: Width w can be specified in two ways:

under the General tab in the Reach Properties dialog, or

as an additional item in the rating curve table under the Hydraulics tab.

With this option, depth must be given as a time series. Then, water volume V is

(5.16)

where l is reach length (to be specified also) and h is water depth.

Residence time T is calculated as

(5.17)

where Q is the reach outflow rate (by convention, it could also be argued that Q should be the average of inflow and outflow rates, if those differ due to routing).

Width (using calculated depth): Same as "Width and depth", but water depth is taken from the calculations rather than as an input time series. This option requires that water depth can be calculated, thus you must choose either Manning's formula or the rating curve option under the Hydraulics tab.

Based on routing: Provided you have chosen a kind of routing calcula-tion, the reach storage S is calculated already, so the residence time can be found as

(5.18)

Reach length is not required.

The Parameter Set input indicates the reaction parameters that apply for the reach. Because often, there is little spatial variability in these parame-ters, they are not specified in a tab page for each reach. Rather, you can define a number of parameter sets and then choose among those. The New button lets you define an entirely new set, whereas the Edit button lets you edit the parameter set selected in the combobox. Parameter sets are dis-played by their names, which you are free to set. The parameters con-

V w l h⋅ ⋅=

T VQ----=

T SQ----=

56 MIKE BASIN

Water Quality

tained in the set are explained in the Water Quality Modeling (p. 159) section. When you create a new set, all parameters have default values.

Weir height is only required when you model DO, with re-aeration mod-eled to occur at weirs. The height should be set to the sum of all weir heights along a reach. For details on the calculations, again see the Water Quality Modeling (p. 159) section.

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58 MIKE BASIN

Simple Node Properties

6 RIVER NODESRiver nodes are automatically inserted at each end of a river reach, and at points where reaches intersects. River nodes may, however, also be inserted manually by using the River Node Tool in the MIKE BASIN tool-bar ( ). There are two different types of river nodes:

simple nodes, and

bifurcation (Diversion) nodes

The two river node types are illustrated in Figure 6.1

Figure 6.1 Simple Nodes and Diversion Nodes

A river branch can be divided into two downstream river branches at a node. In that case the node becomes a Bifurcation Node. For a bifurcation node the conditions at the point of bifurcation needs to be specified. A bifurcation node cannot be an offtake node.

The properties of Simple Nodes and Biforcation nodes are described below.

6.1 Simple Node Properties

As illustrated in Figure 6.1, simple nodes can be offtake nodes (extraction points) or return flow points for surface water extraction for Water Users or Irrigation Usage. Several users may share the same offtake node.

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6.1.1 Priority of Downstream DemandWhen more than one user is connected to the same node, a set of rules that defines how the available water is allocated in case of water shortage is required. Two different options are available:

1 Supply by priority: Each of the water users are getting their demand fulfilled in order of priority, i.e. each water user is assigned a priority and the demands will be fullfilled according to the assigned priorities.

2 Supply by fraction of flow: Each user is assigned a fraction of the available water at the offtake node. The sum of the assigned fractions must be equal to one. When the Fraction of Flow rule is used, the water users are assigned the same priority. The fractions are provided as time series

Allocation rules are specified in the Nodes Properties dialog. Each water user is represented by one rule. The rules are listed in the rules table (Pri-ority of downstream demand) of the properties dialog (Figure 6.2).

Figure 6.2 Properties of an offtake river node that supplies four water users. Two nodes share the first priority (Fraction of Flow rule), and the remaining users are supplied by priority (Supply by Priority).

Rules are added and deleted with the buttons in the right-hand side of the table control. To change the type of a rule, delete the old rule and insert a new rule of the selected type.

60 MIKE BASIN

Simple Node Properties

When a new node is added, or when an existing rule is edited, the dialog in Figure 6.3 appears.

Figure 6.3 Edit Rule dialog for river nodes.

If the Supply by priority rule is selected, a priority number has to be spec-ified for each water user. The number 1 specifies the highest priority, the number 2 the second highest priority and so forth.

If the Supply fraction priority is selected, a time series file needs to be specified for each water user. The time series should contain the fraction of the flow to be supplied to the water user. The fractions for all users within a group (i.e., all those that receive a fraction of the flow) should add up to 1 at all times. The same priority must be specified for each user.

It is legal to specify multiple groups of users with fractional supply, where each group has a shared priority. It is also legal to "mix" the two types of supply rules as illustrated in Figure 6.2.

Illustrating how a supply rule worksIn Figure 6.4 is shown a small schematic setup in which water is distrib-uted to three water user nodes. The available flow in the river is constant equal to 10 m3/s at the river node. The three water user nodes have the fol-lowing water requirements: the City(W4) requires 5 m3/s, and the Vil-lage(W5) and the Industry(W6) require each 4 m3/s. The following rule was specified for the Supply node (see Figure 6.2):

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City: 1. priority

Village and Industry: 2. priority, sharing 50/50 (described by a time series)

Figure 6.4 Simple example setup of supply rule for three water user nodes.

The simulation yields the following supply to the water user nodes:

City: 5 m3/s, Village and industry: each 2.5 m3/s.

Notice that the City is not restricted, whereas the Village and the Industry both experience an equal deficit.

6.1.2 Minimum Flow RuleThe node can have a minimum flow rule: a minimum flow, as specified in an attached time series file, shall be allowed to pass the node (passing flow) to the downstream before any water is extracted for water users con-nected to the node. A minimum flow rule is specified by clicking on the Add... tool , and a new dialog for specifying the time series file and data appear.

Note: Minimum Flow Rule is a local rule. It is not to be used to control the discharge in remote locations.

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Edit Rule dialog for specifying minimum flow requirements.

6.2 Bifurcation Node properties

By clicking on a river node that represents a bifurcation point, the 'Bifur-cation node' dialog will appear for editing the attributes

There are two possible choices for bifurcation:

1 Specified bifurcation in a Time series file, where the flow to the minor river (the diverted water) is a function of time (though limited by the available net flow to the bifurcation node). When choosing this option, you must supply a time series of bifurcation 'demand'.

2 Bifurcation curve, where the flow to the minor river (the diverted water) is a function of the net flow to the bifurcation node. When choosing this option, you must supply a table that defines this relation-ship.To avoid an error due to the need for extrapolation, the table should have (0,0) as its first row and a large value in the first column of the last row. Any limited capacity of the bifurcation channel can be modeled by specifuing the capacity limitation for the bifurcation reach.

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64 MIKE BASIN

Schematic Catchments

7 CATCHMENTSCatchments provide inflow to the MIKE BASIN river network, and a MIKE BASIN model may contain any number of catchments.

Catchments may be represented schematically, or by their delineated boundaries as illustrated in Figure 7.1. The only difference between sche-matic and delineated catchments is that the area can be derived from the delineated catchments whereas it has to be specified for the schematic catchments.

If the inflow at some reaches is considered to be insignificant, catchments may be omitted.

Figure 7.1 MIKE BASIN Catchments (green areas) may be represented sche-matically (right) or by the delineated catchment boundaries (left).

7.1 Schematic Catchments

Schematic catchments are added to the model by using the Add Catch-ments button in the MIKE BASIN toolbar. When the button has been presed, catchments are added by clicking at a point along the river net-work. When a catchment is added it will by default be a schematic catch-

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ment that is represented by a green catchment node and a shape representing the catchment area as shown in Figure 7.2.

Figure 7.2 Schematic catchment

The schematic catchment will extend from the catchment node to the near-est upstream river or catchment node. Runoff from the catchment will be added to the river network in the catchment node. A river node can be changed to a catchment node by clicking in Add Catchment mode on a river node.

7.2 Delineated catchments

Delineated catchments can be added to a MIKE BASIN model in two dif-ferent ways, by importing the shapes from an existing shape file, or by deriving the catchment with the catchment delineation tool of MIKE BASIN. The two methods are described below.

7.2.1 Importing catchment shapesIf you have catchment shapes in an existing shapefile, you can copy these shapes to your river network. First, add the shapefile to the ArcGIS Table of Content using the "Add Data…" command in the ArcGIS File menu, or use the corresponding button on the Standard toolbar ( ).

Tip: Once you've added the layer, drag it below the MIKE BASIN catch-ments layer in the table of contents. This way, as the shapes are copied to the MIKE BASIN model, you will see the new MIKE BASIN catchments appearing over the shapes you are copying. Otherwise, the new catch-ments will be hidden by the original shapes.

Then, select "Copy Catchment Shapes…" from the MIKE BASIN menu, which will display the dialog shiwn in Figure 7.3:

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Delineated catchments

Figure 7.3 The Copy Catchment Shapes dialog

Select the layer with the catchment shapes you want to copy in the drop-down list. Then click on the Select catchment shape to copy from tool button. On the map, click on the catchment shape you want to copy.

The dialog will now automatically switch to the second tool so you can assign the shape to a branch. Click on the reach you want to assign the catchment to. The downstream node of the selected branch will turn into a catchment node, and the selected catchment shape will be copied to the MIKE BASIN Catchments layer..

Note: You can assign a shape to a branch which flows to a standard river node or reservoir. The river node or reservoir will automatically convert to a catchment node, and a new catchment will be added with the shape you are copying.

7.2.2 Delineating catchmentsCatchment shapes may be delineated using an elevation model. The most accurate, method is to derved the catchments from a detailed elevation model, but if such DEM is not available, MIKE BASIN has a tool that can be used to create a so-called pseudo-DEM based on the river network

Important: Catchment delineation in MIKE BASIN requires the ArcGIS Spatial Analyst Extension.

Before a DEM can be used to derive catchments from (that be a real DEM or a pseudo-DEM), it needs to be processed. First, add your DEM to the project using the “Add data” button in the ArcGIS main toolbar ( ).

Next, open the tools for processing the DEM from MIKE BASIN drop-down menu (Process DEM...).

The Process DEM dialog is shown in Figure 7.4

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.

Figure 7.4 The process DEM dialog.

To process the DEM, select your DEM from the drop-down list, and click Calculate Flow Direction. This will produce a new layer that contains flow direction. The new flow direction layer will be used by the catchment deli-ation tool, and when the flow direction layer has been produced, the catch-ment delineation tool ( ) will be enabled in the MIKE BASIN toolbar.

Before applying the catchment delineation tool, add any number of sche-matic catchments. When the Catchment Delineation button is pressed, the schematic catchments will transform into the corresponding delineated catchments.

Creating a pseudo-DEMIf a detailed DEM is not available, a pseudo-DEM can be created using a shape file that contains the river network. A pseudo-DEM is created by "pressing" a river network into a flat grid (a “rubber-sheet”), such that all cells in the produced pseudo-DEM slope toward the nearest river. The dia-log is shown in Figure 7.5.

Figure 7.5 Pseudo-DEM dialog

68 MIKE BASIN

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To create a pseudo-DEM you will need a river layer and a basin layer from the drop-down menus. The basin layer should contain a polygon (or a number of polygons) that outlines the entire river basin. The pseudo-DEM is created when OK is pressed and the catchments are delineated as described in 7.2.2.

Notice that the river layer should cross the outer boundary of the basin layer only at the outlet. This point will define the flow direction.

Tip: Processing time goes up exponentially as the cell size gets smaller. On the other hand, if the cell size is too large, it will not be able to capture the detail of the river network. Try a size about 1/3 the smallest distance between rivers.

Adjust DEM elevationsMany DEMs contain inaccuracies because of their resolution or artifacts in the method of creation. When delineating catchments and rivers from the DEM, you may find some unexpected results. This can particularly happen in flat areas where DEMs may not have the vertical resolution to correctly delineate the rivers and watersheds. Even small errors can have large consequences when, for example, a sub-catchment has a low point along its divide close in elevation to the true outlet. If the DEM cell at this low point is just slightly lower than the outlet, all the water may get routed out to a neighboring basin instead of downstream. In order to correct the DEM to more closely match known flow patterns and catchment divides, you can use the Adjust DEM tool.

The Adjust DEM tool allows you to adjust the DEM with known river lines and catchment boundaries. If you have a map layer with known river channels, it is possible to force a DEM to match these. The cells through which rivers run are lowered by a user defined amount or all the way to the minimum value of the DEM. This is called "burning" the rivers into the DEM. Cells which do not lay on the river channels are not changed. You can also raise "walls" or barriers at known catchment divides. This will still allow you to subdivide the entire basin based on any catchment nodes you wish.

Open the Process DEM dialog by selecting Process DEM… from the MIKE BASIN menu.In the combo box, select the DEM you want to adjust, then click on the Adjust DEM Elevations button, which will dis-play the following dialog:

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Select the layer with the shapes you want to use to adjust the DEM. If you use a layer with polygon shapes, the entire area of the polygons will be raised or lowered, unless you check the "Only adjust perimeters of poly-gons" option, in which case only the outlines will be used for adjustment.

Then select the type of adjustment. This determines how the elevation will be altered at all cells which are covered by the shapes. Although it may seem extreme, best results are often obtained by simply burning rivers down to the minimum elevation. The original DEM will not be altered; a new grid will be created instead. Note that it is not necessary to burn rivers when using a pseudo-DEM.

Important: If you raise the DEM values to the maximum based on some known catchment divides, make sure the divides have an "opening" at the outlet of the sub-catchment, so the routine can determine where the water flows out. This can be done by first raising the divides, then burning the rivers into the DEM down to the minimum.

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General catchment properties

7.3 General catchment properties

Catchment properties are accessed by right-clicking on a catchment fea-ture and selecting “MIKE BASIN Properties”. The properties dialog is shown in Figure 7.6

Figure 7.6 Catchment properties dialog.

Catchment areaWhen catchment runoff is specified as specific runoff rates (e.g. lit-ers/sec/m2) an accurate specification of the catchment area is required in order to calculate the runoff volume (area x specific runoff). When the runoff volumes are specified as discharges (e.g. m3/s), the catchment area is not used.

Catchment areas can either be assigned manually, or calculated automati-cally based on the catchment shapes. For schematic catchments a manual specification of the catchment area is normally required, whereas the cal-culated area can normally be used for delineated catchments.

The preferred catchment area specification method is selected by checking and unchecking the “Use shape area for assigned area” checkbox. Per default MIKE BASIN uses the calculated catchment areas.

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Catchment RunoffCatchment runoff can be specified either as specific runoff or discharge. The type of runoff is determined entirely by the item type of the runoff time series. Valid item types are ‘Specific runoff’ (volume per time per unit area) or ‘Discharge’ (volume per time). When a groundwater model has been activated the catchment runoff will represent the fast catchment response and it will be added directly to the river without being routed through the groundwater reservoirs (section 7.4).

If the specified time series does not cover the entire simulation period, it will automatically be recycled (see section 3.2).

7.4 Groundwater

Optionally, groundwater processes can be included in a catchment model. The underlying conceptual hydraulic model is the linear reservoir model with one or two aquifers (fast/slow response). The conceptual structure of the two-layer groundwater component is illustrated in Figure 7.7. Single-layer models only include the deep reservoir.

Important: Accessing and enabling the groundwater models requires that the groundwater option has been checked in the MIKE BASIN Options menu (reference).

Figure 7.7 Conceptual structure of the MIKE BASIN groundwater component.

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As illustrated in Figure 7.7 groundwater interacts with the surface water via groundwater recharge, groundwater discharge and stream seepage. Moreover, when the depth to the water table of the upper reservoir reaches the land-surface, it starts to spill directly into the river. Finally, groundwa-ter from the deep aquifer can be pumped by water users.

The groundwater model type can be selected from the ‘Groundwater model’ pull-down menu (None/single-layer/two-layer) under the ‘Gen-eral’ tab (Figure 7.6).

7.4.1 Linear Reservoir modelIn a linear reservoir model, groundwater discharge, i.e., flux through the outlet(s) is proportional with water level, and because catchment area is constant, it is also proportional with storage. Specifically, the coupled dif-ferential equations solved are:

(7.1)

(7.2)

where the variables related to the geometry (h and L) and time constants (k) are defined in Figure 7.8. The fluxes (q) are illustrated in Figure 7.7. The dimensions of L and h are [Length]. Note that an (outflow) rate con-stants k [1/Time] are the inverse of the outflow time constant that is speci-fied in the catchment properties dialog. The fluxes q in the equations are area-specific [Length/Time].

Figure 7.8 The geometry of the linear reservoir model.

∂h1

∂t-------- k1– ki–( ) h1 L1–( ) qrech earg qstream_seepage+ +=

∂h2

∂t-------- ki h1 L1–( ) k2 h2 L2–( )– qpumping–=

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The mathematical solution of the linear reservoir equations in MIKE BASIN is valid also for situations where the groundwater storage is emp-tied (when outflows permanently exceed inflows), or when overflow occurs (when inflows permanently exceed outflows). This is also valid when the deep groundwater level reaches the shallow outlet, causing flow back into the shallow reservoir.

7.4.2 Groundwater Model TabThis dialog is only available if the groundwater option has been selected in the MIKE BASIN Options menu. By default the menu assumes no groundwater reservoir model for the catchment. In such a case groundwa-ter can not be utilized. If you have NOT selected the groundwater option in the options dialog, groundwater can still be utilized simply through the specification in the water user time series file (see 8 Water User Nodes (p. 79)), but groundwater is assumed to be an unlimited resource with no feedback to the surface water system.

In MIKE BASIN, it is assumed that the boundaries of subsurface (ground-water) and surface catchments are the same The groundwater storage (aquifer) is conceptualized as a linear reservoir system with one or two (optional) layers. Depending on your choice a number of groundwater parameters needs to be specified.

For both single- and two layer models, parameters are assigned under the ‘Groundwater’ tab (Figure 7.9).

74 MIKE BASIN

Groundwater

Figure 7.9 The Groundwater tab.

The input parameters to be specified in the dialog below are:

Aquifer Characteristics - Shallow AquiferDepth (relative to ground surface) to the initial water table. The intial water table depth can determine the magnitude of the groundwater dis-charge and the available water for pumping in the intial period of simula-tion. Depending on the time constant specified it may influence the results from days to several months of the simulation.

Depth to the outlet. The depth to the outlet determines the storage capac-ity of the shallow aquifer. The water table can vary between that depth and up to ground surface (depth = 0 meter) at which time overflow of ground-water discharge may occur to the river.

Time constant. The time constant determines the rate of which the groundwater aguifer discharges water to the river (as baseflow). The larger the time constant to longer it takes and the more constant is the baseflow contribution.

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Note that groundwater pumping is assumed to take place from the deep aquifer unless a one-layer aquifer has been specified.

Aquifer Characteristics - Deep AquiferDepth (relative to ground surface) to the initial water table. The intial water table depth can determine the magnitude of the groundwater dis-charge and the available water for pumping in the intial period of simula-tion. Depending on the time constant specified it may influence the results from days to several months of the simulation.

Depth to the outlet. The depth to the outlet determines the storage capac-ity of the shallow aquifer. The water table can vary between that depth and up to outlet depth of the shallow aquifer.

Time constant. The time constant determines the rate of which the groundwater aguifer discharges water to the river (as baseflow). The larger the time constant to longer it takes and the more constant is the baseflow contribution.

Bottom level. This is the highest depth from which water can be drawn from the deep aquifer. This indicates the total storage available for usage from the deep aquifer.

Time constant in the interface between shallow and deep aquifers. The constant determines the rate of which water percolates from the shallow aquifer to the deep aquifer.

Groundwater Recharge Time SeriesThe reference to the recharge time series file (See also time series selec-tion). The file must contain information about either the specific recharge (volume per time per-unit area) or the recharge (volume per time). Please note that the runoff time series, when groundwater models are included, only covers the surface/interflow components of the hydrograph.

7.5 Water Quality

This time series determines solute transport from the catchment to the river via surface runoff. The time series group can contain time series for any number of the solutes modeled by MIKE BASIN. Data in the time series can be concentrations, absolute mass fluxes, or area-specific mass fluxes. Internally, area-specific mass fluxes are multiplied by catchment area, and concentrations are multiplied by total runoff, to give absolute mass fluxes.

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The Water Quality in Runoff Time Series can be specified manually, but is most conveniently computed and filled in by the Load Calculator (p. 169).

When modeling both groundwater and water quality, solute also enters the river through groundwater discharge. Also, when there is overland flow generated by a water level reaching the ground surface, and the water quality time series contains concentrations, then these apply to overland flow as well.

7.5.1 WQ in Groundwater tab This tab is active only when both the groundwater and the water quality options are selected in the Options dialog. See Options (p. 25).

In the top part of the dialog, you can specify any first-order decay rates. These apply to the four most relevant substances. Depending on whether you have chosen a 1- or 2-layer groundwater model, you can fill in 1 or 2 sets of parameters. A decay rate of zero implies conservative transport. The equations solved are shown in the Water Quality Modeling (p. 159) section.

The initial state, like in reservoirs, can be either pristine or steady state. Pristine means zero concentration of any substance. At steady state, con-centrations in groundwater recharge (below) equal those in groundwater discharge, i.e., the concentrations in groundwater must be equal to those in the recharge boundary time series for the simulation start time.

The Water Quality in Groundwater Recharge Time Series determines sol-ute transport from the catchment surface to groundwater. In terms of allowed data, it is analogous to the Water Quality (p. 76). If it is a concen-tration time series, it is multiplied by groundwater recharge to yield a mass flux

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78 MIKE BASIN

8 WATER USER NODESWater User Nodes are a water consuming activity from the river network, or reservoirs, and MIKE BASIN may contain any number of Water Users. Water User Nodes can represent municipal, industrial or any type of water supply. Water extraction for irrigation purposes has its own node.

Figure 8.1 MIKE BASIN Water User Nodes representing extraction from river and reservoir nodes.

The temporal variation in the extraction of water is described by a time series file for each water user node. Water can be extracted from one or several river nodes and reservoir nodes, as well as ground water storage. The temporal variation of return flow of water that is assumed not to be consumed at the water user node can be transferred back to one or more river nodes. The transfer can also be described by a time series file.

In many situations several water users are extracting water from the same river section. In such situations it can be an advantage to lumped these into one scheme described by a single water user node.

You include Water User nodes in the model by inserting these in the View away from rivers using the Digitize Water User button in the MIKE BASIN toolbar.

You use the Add Channel button to connect a Water User node to its upstream extraction point or downstream return flow point on rivers or reservoirs. The digitization of a channel is always down in flow direction, i.e. from extraction point to water user, or from water user to return flow point.

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8.1 General Water User Properties

The attributes are specified in the Water User Properties dialog, which is accessed by using the MB Feature Properties tool and subsequently click on the water user feature to be edited. You can alternatively right click on the Water User node and selecting Mike Basin Properties. The properties dialog is shown in Figure 10.2.

Figure 8.2 Water User properties dialog

CategoryIf you wish to distinguish between different water user types, you should specify a descriptive name that identify what category the water user belongs to, and can be further analysed in connection with result presenta-tion. Examples of Category names could be: municipal water supply, industrial water supply, major cities, villages etc.

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Water Use characteristicsA time series file can be specified by either clicking on the New… or the Open…button. Clicking on the New… button provides access to a default time series, which can be renamed and saved. Clicking on the Open… but-ton provides access to an existing time series file of the correct type.

The time series file must have the following four items:

Water demand. The total amount of water that is required to be extracted to fulfill the water demand of the Water User.

Deficit carry-over fraction (from one time step to next). Generally in MIKE BASIN, the allocation solution is only with respect to demands in the current time step. In particular for irrigation schemes, however, it may be more appropriate to allow deficits to carry over from one time step to the next, resulting in a larger demand in that next time step (larger than the "normal" demand given in the demand time series). This item in the time series can be used to specify the fraction of any deficit that should carry over to the following time step. Mathemati-cally this is described by:

D'(t+1) = D(t+1) + f(t) * X(t) (8.1)

Where D'(t+1) is effective water demand at time t+1, D(t+1) is water demand as given in the input time series for time t+1, X(t) is deficit (unsatisfied demand as calculated by MIKE BASIN) and f(t) is the carry-over fraction, the latter two at the previous time step t. D', D, and X have units of volume, while f is dimensionless.

In other words, f = 0 reverts to the regular MIKE BASIN solution, whereas f = 1 indicates 'perfect memory' for deficits.

Note Results from monthly simulations may appear to 'oscillate'. This is not an error, but rather because the deficits in the above formula are absolute volumes, whereas demands in the input time series must be given as flows (volume per time). Due to the different lengths of differ-ent months, a constant deficit in terms of flow means a varying deficit in terms of volume.

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Groundwater use fraction. This time series item specifies the fraction of the total water demand or the remaining demand (after the supply has been attempted to be covered by surface water) that should be ful-filled from groundwater. Without the groundwater extension enabled in the MIKE BASIN Options (p. 25) dialog, MIKE BASIN assumes that any groundwater demands described by this item in the water use time series file can always be fulfilled (unlimited reservoir capacity). With the extension enabled, actual groundwater extraction depends on the state of the linear reservoir.

Groundwater absolute demand. This time series item specifies the total demand that should be covered by groundwater. This item may only be in use if the groundwater extension is enabled in the MIKE BASIN Options (p. 25) dialog. With the extension enabled, actual groundwater extraction depends on the state of the linear reservoir

Default demand time series for Water Users is shown below. See, Time Series Selection for selecting, plotting and editing this time series.

Priority of Upstream Supply NodesAfter linking the water user node to one or more upstream river nodes the rule selection fields will then automatically be filled with the upstream supply nodes corresponding to the various extraction points for the water user.

You can now edit the individual water extraction rules by clicking on the Edit… tool. Editing will be available for the row with the pointer. A new Edit rule dialog will appear:

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General Water User Properties

Specify the type of extraction rule that should apply. Two types of rules are available:

Call by priority. Water is extracted from upstream nodes to satisfy the demand in the order of priority beginning with nodes having the lowest priority number.

Call by fraction of demand. Water is extracted from each upstream node based on the fraction of the demand required from each node. If an upstream node cannot fulfil its fraction there is no attempt to extract water from another upstream node.

The time series to be specified must contain the fraction of demand requested from each upstream node (supplier). Note that for all times in the simulation, the sum of fractions must not exceed 1. It is legal, how-ever, to have a sum less than 1, with the remainder showing in the results as "Water Demand Deficit". Be careful, however, that such a deficit and a "true" deficit due to lack of water can be hard to distinguish from one another.

The characteristics of the channel from each extraction point to the water user node are described in the Reach properties dialog. See General River Reach Properties (p. 47). The reach property dialog is accessed by right clicking on the channel feature.

Return flow rule(s)If return flow occurs from the water user node to, for example, the river, a channel should be created between the Water User node and one or more

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Water User Nodes

down stream nodes. The return flow rule fields will automatically be filled with a number of downstream nodes corresponding to the number of downstream return flow nodes from the water user node.

For entering a time series click on the Edit rule… button. In the Edit rule dialog a new time series can be specified or an existing file can be opened. The downstream node reference is already filled in.

The time series to be specified must contain the return flow fraction for each downstream node. Note that for all times in the simulation, the sum of return flow fractions must not exceed 1. It is legal, however, to have a sum less than 1, with the remainder showing in the results as "Used Water.

8.2 Groundwater

Under the Groundwater tab the following data should be specified:

There are three different options for using groundwater to fulfill the Water User demand:

Fraction of total demand. This method will attempt to fulfill demand by taking a fraction of the total demand from the groundwater, as spec-ified in the Water Use time series under the general tab. This option correspond to a specified sharing of the surface water and the ground-water resources. If there is a limited water available either in the sur-face water or the groundwater the demand will not be fulfilled.

84 MIKE BASIN

Water Quality

Fraction of remaining demand. This method will attempt to take a fraction of the demand that can not be fulfilled by surface water as specified in the Water Use time series under the general tab. If the frac-tion is set to 1.0 it means that the water user first extracts surface water and then fulfills the rest by groundwater. This option corresponds to specified priority between surface water (first priority) and groundwa-ter.

Absolute demand. This method will calculate the demands from sur-face water and groundwater respectively and then attempt to take this from each resource independently. Notice that in this case the ground-water demand could be higher than the total demand specified. In such cases the surface water extraction will be zero.

Supplying CatchmentIn this field you can specify the catchment from which the groundwater is taken. By enabling the tickbox, only valid catchments for which ground-water aquifers exist will be displayed in the pull down menu.

8.3 Water Quality

Water users are modeled as point sources, for example, a city's wastewater treatment plant. Water quality in the effluent from a water user is specified as a time series.

The time series group can contain time series for any number of the sol-utes modeled by MIKE BASIN. Data in the time series can be concentra-tions or absolute mass fluxes. Internally, concentrations are multiplied by return flow, to give absolute mass fluxes.

You can choose between two options of how to have the effluent boundary condition interpreted in the MIKE BASIN calculations.

If you know (from measurements) the effluent concentration, choose the option to have any incoming (to the treatment plant) solute ignored. Your measurements already include the effect of the treatment, so you are not making a mistake even though the incoming solute mass is not preserved.

To model mixing of solutes in the inflow to the user and in additional sources represented by the user, choose the option to add the two. The effective concentration is the flow-weighted average of incoming and source concentrations.

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Water User Nodes

86 MIKE BASIN

9 RESERVOIRS

MIKE BASIN accommodates multiple multi-purpose reservoir systems. Individual reservoirs can simulate the performance of specified operating policies using associated operating rule curves. These define the desired storage volumes, water levels and releases at any time as a function of cur-rent water level, the time of the year, demand for water, and losses and gains.

Reservoirs can be inserted anywhere on the river branches except on river bifurcation nodes or the most upstream nodes. Inserting a reservoir on a river branch does not require that a river node is already added on that location. Reservoir nodes replace river or catchment nodes once placed on top of these.

There are three types of storage types that can be modeled in MIKE BASIN and the input requirements will depend on the reservoir types selected.

Rule curve reservoirs regard the reservoir as a single physical storage and all users are drawing water from the same storage. Operating rules for each user apply to that same storage and the users compete with each other to fulfill their water extraction rights.

The Allocation Pool reservoir has also a physical storage, but the individ-ual users have been allocated certain storage rights within a zone of water levels. An accounting procedure keeps track of the actual water storage in one pool for downstream minimum flow releases (water quality pool) and in individual pools allocated for water supply users. Thus, a particular water level is not uniquely related to a set of volumes in all pools (one can 'shift' some volume from one pool to another without any effect on water level).

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Reservoirs

Lakes are specific reservoirs for which no operation rules apply. The out-flow from a lake can be restricted by a spillway relationship. If no such is given and the water level is at the top of dead storage, all inflow to the lake will flow out immediately.

When simulating systems with reservoirs, it is recommended to use small time steps (days). During large time steps, water levels might move through several zones in the operating rule curves, making results inaccu-rate.

9.1 General Reservoir Properties

The the reservoir characteristics, operating rules, and upstream- and downstream connections to users and control nodes are all specified in the reservoir properties dialog

Note: It is specified explicitly in the descriptions below when the data entry for the Allocation Pool reservoir deviates from the Rule Curve Res-ervoir.

88 MIKE BASIN

General Reservoir Properties

Level-area-volume tableComputing water levels in a reservoir requires the relationship between elevation, volume, and area (HVA) to be known. This information must be specified as a table in a file.

This is entered in a file with three items in a tabular form similar to time series data. In this particular case, the time specification in the first item is replaced by 'X' values describing the elevation.

The table is checked for physical plausibility in MIKE BASIN. Particu-larly, it should hold that

(9.1)

Where i is the i’te value in the table of increasing water level elevations H. In other words, for every step in elevation, the increase in volume should at least be the base area (at the previous level) times the increase in height.

V H i 1+( )( ) V H i( )( ) A H i( )( ) H i 1+( ) H i( )–( )⋅+≥

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Reservoirs

A smaller increase corresponds to a 'narrowing' reservoir (as water level increases). A warning is issued at the end of the simulation if the above situation is detected.

During the simulation, linear interpolations between the user-specified neighboring data triplets in the table is performed to arrive at a piece-wise linear HVA function.

Note: If the calculated reservoir water level is outside the range of tabular values specified in a HVA file during a simulation, an error message will appear on the screen. No extrapolation is carried out beyond the range of the specified elevation values in the HVA file.

If a preliminary simulation is nonetheless desired, a work-around is to specify the reservoir level in the HVA table to start at zero and end at a very high level. This will avoid the necessity to extrapolate and thus an error message.

Characteristic levels time seriesThe following reservoir information is always required:

Bottom Level, which is the bottom of the reservoir

Top of Dead Storage, which is the minimum level from which water can be utilize. If the water level is below this zone water can only be lost due to evaporation or bottom infiltration.

Dam Crest Level, which is the highest level the water can reach in the reservoir before spill occurs.

Losses and gains time series (optional)The following three loss / gains time series can be entered :

Precipitation

Potential evaporation

Bottom infiltration

The loss/gains terms goes into the water balance calculations and the actual loss in each time step (in terms of volume per time unit) will depend on the actual water level in the reservoir at that time step.

90 MIKE BASIN

Rule Curves Reservoirs and Lakes

9.2 Rule Curves Reservoirs and Lakes

The operation tab for reservoirs and lakes gives access to specifying the reservoir operation rules. They are specified in the following four sec-tions:

Operation rules (p. 92) - Operating rules are defined to include not only storage target levels (e.g. the flood control level in case spillways information is not specified), but also various storage allocation zones, release and spill requirements and constraints respectively. These can vary in time as described by rule curve time series.

Priority of downstream users (p. 94)- Reservoirs can directly be con-nected to multiple downstream water user nodes, hydropower nodes or reservoir nodes. The rule field will automatically be filled when you connect downstream nodes to the reservoir in connection with the model creation. You can edit the priority rules for each downstream user by pointing on the row and clicking on the Edit Rule… or double clicking on the pointer.

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Reservoirs

Remote Flow Control (optional) (p. 98) -Remote flow rules are special in that unlike all other rules in MIKE BASIN, they are logical relations between nodes far away from each other - not neighboring nodes. Use remote rules if you have a control point somewhere far downstream from the reservoir, possibly with many intermediate inflows and offtakes. Remote flow rules are also useful if you have users not con-nected immediately to a reservoir, but to be supplied by it. Just define a remote minimum flow rule with reference to the offtake river node that the user draws from.

Storage Demand (optional) (p. 99) - The Storage Demand rule is a way of operating two reservoirs in series or in parallel. If two reservoirs are located on the same river branch in series it is often an advantage to keep as much water as possible in the upstream reservoir The storage demand option will ensure that water is released from the upstream res-ervoir for the downstream reservoir only to maintain a certain critical water level in the downstream reservoir.

In the cases where the Allocation Pool Reservoir type is used, the Priority of Downstream Users is replaced with the Allocation pool owners demands. See Rules specifically for Allocation Pool reservoirs (p. 101).

Operation rulesOperating rules are specified to define not only storage target levels, but also various storage allocation zones. These can vary in time as described by rule curve time series. Operating rules are also specified to define release and spill requirements and constraints respectively.

The following rule time series are available:

Flood Control level (mandatory)

Minimum operation level (optional)

Minimum release requirement (optional)

Maximum release constraint (optional)

The Flood control level entry will always appear for rule curve or alloca-tion pool reservoirs.

Minimum downstream release can be regarded as a minimum environ-mental release to support the flow in the river downstream of the reservoir during critical periods of drought. This release takes place as long as the water level is above the Top of Dead Storage level.

Maximum downstream release can be regarded as a restriction on the flood control release when the water level in the reservoir is above Flood

92 MIKE BASIN


Control Level or the Spillway Bottom Level (optional). The Maximum release is specified as a time series in the rule curve time series.

All above parameters are specified as time series items in the rule curve time series.

When editing or adding a rule the follow dialog appears:

You can select the specific rule and subsequently specify a time series file.

Based on the above rule curve levels and the reservoir characteristics, the reservoir can be divided into five zones:

Flood Control ZoneThis zone serves as storage buffer to diminish the impacts of high floods. Under normal circumstances the water level in the reservoir is kept at flood control level to maintain optimal protection and reserve water for supply. If the water level is within the flood control zone water is released at a rate up to maximum downstream release. The release can be limited by spillway conditions.

If a spillway Bottom Level time series is specified (see the Spillways sec-tion) the lower level of flood control zone is defined by the Spillway Bot-tom Level, no matter this is above or below the Flood Control Level.

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Reservoirs

Normal Operating ZoneThis zone is between the lower level of the flood control zone and the first Reduction Level for a given water user. In this zone all demands are ful-filled. The extend of this zone can vary for indivídual water users

Reduced Operating ZoneIf the water level is in this zone, a demand is only partially fulfilled. A var-iable number of reduction level curves and corresponding reduction fac-tors can be specified for each connected water user as described below. The lower limit of the Reduced Operating Zone is the Minimum Opera-tion Level. If this level is not specified then the lower limit is the Top of Dead Storage.

Conservation ZoneIf the water level reaches this zone, only downstream release (Minimum release requirement for conservation purposes is maintained). No water for usage is being released. Allocation pool reservoirs do not have a con-servation zone, but rather a 'water quality' pool for the same purpose.

Priority of downstream usersYou can connect multiple water user nodes, hydropower nodes and reser-voir nodes to a reservoir. The rule field will automatically be filled when you connect downstream users to the reservoir in connection with the model creation on the screen. You can edit the priority rules for each

94 MIKE BASIN


downstream user by pointing on the row and clicking on the Edit Rule… or double clicking on the pointer. The following dialog appears

You can specify the following data:

Priority You can give a priority among downstream user nodes. Number 1 has highest priority, the number 2 and so forth. Notice, that minimum release to a downstream river node always has higher priority than any down-stream user nodes. In order for a down-stream user to effectively have first priority, the specified downstream release for the reservoir must be set to zero.

Rule dataYou can specify operating rules for supplying water to the individual water users. This is done by specifying time series pairs of water levels and corresponding reduction factors of the demand to be supplied. This is particular relevant for drought management.

When the reservoir water level falls below Reduction Level 1 for a spe-cific user, the actual extraction is calculated as the water demand times the specified Reduction factor 1. If the reservoir water level falls below Reduction Level 2, a more drastic (smaller) Reduction factor 2 is applied, and so on. Each user has its own set of reduction levels as specified by individual rule curves given in the dialog for each user.

After the first time series of corresponding reduction level (level 1) - reduction factor has been specified (e.g. by clicking on the New... tool),

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Reservoirs

subsequent time series can be given by clicking on, the Add Reduction Level … tool. In this way you can specify as many reduction thresholds as required. Plot the time series to see the additional thresholds and for edit-ing them.

The figure below illustrates how different reduction levels and factors can apply to different water user nodes. In the figure the low priority user, e.g. for industial production is getting its demand reduced earlier and more drastically, than the high priority water user, which could be for public water supply.

Illustrating how the reduction rules worksAssuming two water userr nodes are extracting water from a reservoir. The following rules apply for the two water user nodes:

The demand for both water user nodes is 13.89 m3/sec

Operting policy:

User node 1 (W4): Reduction level at :541 m, Reduction factor: 0.8

User node 2 (W6): Reduction level at 540 m, Reduction factor:0.6

The initial water level in the reservoir is 544 m, and the inflow is zero until the 20th January, where the inflow is 35 m3/s

The figures illustrate how the water level is falling as water is extracted from the reservoir. When the water level reaches level 541 m, the with-

96 MIKE BASIN


drawal by user node 1 is reduced to 80%, and the water level falls with a lower rate. When the water level falls below level 540m, the withdrawal to user node 2 is also recuded. Once the inflow to the reservoir starts the water level is rising with a reduced rate as the withdrawal increases.

Note Allocation pool reservoirs have reduction thresholds (fraction of pool volume) instead of reduction levels (reservoir water levels). See Rules specifically for Allocation Pool reservoirs (p. 101) for details.

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Reservoirs

Remote Flow Control (optional)Remote flow rules are logical relationships between nodes that are far away from each other. All other rules in MIKE BASIN are local rules and refer to neighboring nodes.

For example, use a remote rule if you have a control point somewhere downstream from the reservoir, possibly with many intermediate inflows and offtakes. Remote flow rules are also useful if you have users that are not connected directly to a reservoir, but are supplied by it .In this case, define a minimum flow remote rule with reference to the offtake river node that the user draws from.

During the computation, MIKE BASIN will try to adjust the reservoir releases to maintain the control flow limit after considering all inflows and offtakes, and flow delays due to routing.

You can specify more than one remote rule for a reservoir, that is, you can have multiple remote control points. MIKE BASIN will adjust the flow to accommodate them all. Effectively, this means that the most restrictive rule will determine the allowable reservoir release. MIKE BASIN also allows you to have both minimum and maximum remote flow control rules for a reservoir.

After the simulation, in the results, you will find two items that describe the mandatory minimum and maximum flows as determined by both the local and remote flow control rules. For the minimum flow, this will be the larger flow as determined by the local minimum rule or the remote mini-mum rule. Similarly, the actual maximum flow will be the smaller of the local maximum flow and the remote maximum flow.

In the dialog above, clicking on the [Add…] or [Edit…] button will open the following dialog:

98 MIKE BASIN


You can specify the rule type and select the remote control node (here N2). The node can be specified by clicking on the pointer tool and click on the relevant node in the network.You must not select the river node imme-diately downstream of the reservoir as a control flow node. Minimum or maximum flows to that node are determined by the "local" mininum/max-imum release rules in the Operation rule grid.

Storage Demand (optional)The Storage Demand rule is a way of operating two reservoirs in series or in parallel. If two reservoirs are located on the same river branch in series it is often an advantage to keep as much water as possible in the upstream reservoir The storage demand option will ensure that water is released from the upstream reservoir for the downstream reservoir only to maintain a certain critical water level in the downstream reservoir.

The linkage between the two reservoirs in series is specified in the down-stream reservoir only by clicking on the Add… tool. The following dialog will appear to specify the reservoir connection and the rule time series:

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Reservoirs

For two reservoirs in parallel, i.e. not on a single branch, there can be an inter linkage that allows back and forth flow between the two reservoir depending on the actual water levels in the two reservoirs. In such case the rule time series has to specified for both reservoirs. With reservoirs in par-allel means that the two reservoirs are located on different branches that may connect downstream.

The time series for the rule, i.e., the time series with the trigger for demand, must contain a variable of type "Water level" or "Water Volume".

Note As with any other user-supplier relationship, you must also specify a rule of type "supply by priority, managed" at the supplying reservoir. If you want to model bi-directional transfer, both reservoirs must have a storage demand and a supply rule to each other (four rules in total).

The priority of the supply rules must be higher than that of any other user connected to the reservoir(s). Minimum flows still have higher implicit priority in that any minimum releases are performed before any transfer to users or other reservoirs.

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Rules specifically for Allocation Pool reservoirs

9.3 Rules specifically for Allocation Pool reservoirs

The input fields under the Operation tab for Allocation Pool reservoirs are identical apart from that the priority of downstream users are replaced with a rules editing field that specifies the Allocation pool owners. Alloca-tion pool owners can be the Water users and the Hydropower that extract water from the reservoir, and the downstream node that signifies the water quality pool or river augmentation pool for downstream releases. By click-ing on the Edit… tool or the Add… tool the input specification for each owner can be specified in a subsequent dialog, see below.

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Reservoirs

In the time series selection field (see time series selection) a time series can be specified. The time series file contains two items:

Fraction of total storage owned by that water user;

Fraction of inflow owned bay that user.

The sum of the fractions owned by all users including the downstream release right should add up to 1.0.

The downstream release for river augmentation comprises of the mini-mum release plus possible downstream remote flow control points speci-fied under the remote flow control field.

Description of the allocation Pool Reservoir principlesThe reservoir is considered a physical storage (main storage), which is the total storage from the reservoir bottom level to the reservoir full level. In the Allocation Pool Reservoir option the main storage is divided into three physical storages: flood control storage, common allocation storage, con-servation storage.

The common allocation storage exists only if the flood control level has been set above the guide curve, thus allowing storage of water between these two levels. The guide curve corresponds to the top of conservation pool.

The conservation storage is divided into a water quality pool and a number of water supply pools defined by the user. All these pools are purely con-

102 MIKE BASIN

Rules specifically for Allocation Pool reservoirs

ceptual accounting storages used internally in the program, and should not be regarded as physical storages.

Understanding how the Allocation Pool Reservoir works:For each time step (e.g. each day) in the simulation, the reservoir will be simulated as follows:

1 Inflow from the upstream river(s) is added to the reservoir main stor-age.

2 The reservoir level and the surface area are calculated based on the res-ervoir height-area-volume curves.

3 Precipitation is added to the reservoir main storage (based on the actual reservoir surface area).

4 Evaporation losses are extracted from the reservoir main storage (based on the actual reservoir surface area).

5 Bottom infiltration, based on the actual reservoir surface area and a user-defined infiltration velocity, is extracted from the reservoir main storage.

6 The individual water supply pools and the water quality pool are updated by adding a user-defined fraction of total reservoir net-inflow to these pools. If the sum of evaporation losses and bottom infiltration is greater than the sum of upstream river inflow and precipitation, the water volume of these pools will decrease. Any contribution greater than the remaining capacity of the individual pool will spill to a com-mon storage.

7 If there is any water in the common allocation storage, it is distributed to the water supply pools and the conservation pool (if these are not already filled) using the same distribution key as for the reservoir inflow. If all pools are filled during this procedure, the reservoir level will be at or above the guide curve. This means that some water will be available for common use.

8 In order to meet the minimum down stream release requirement (water quality release), water will be subtracted first from the common stor-age if possible, then (if needed) from the water quality storage. In the same fashion, for each individual user in order of priority, the model will try to fulfill the individual water demand. First, water is extracted from the common storage if possible, then (if needed) from the associ-ated water supply pool.

9 Extraction from pool may be reduced due to user-specified reduction volume thresholds and associated reduction factors. The thresholds are specified as fractions of total pool volume. Note that the reduction

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Reservoirs

thresholds are not exactly the same as reduction levels for regular res-ervoirs (i.e., water levels), even though their effect on releases is analo-gous. This is because in allocation pool reservoirs, a particular water level does not define the volumes in all pools uniquely (any amount of water can be 'shifted' from one pool to another without a change in water level).

10 If the reservoir water level, after releasing water to ensure minimum release and distributing water to the reservoir users, is still above the flood control level, water will be released to the down stream river in order to lower the reservoir level to the flood control level. The total release rate from the reservoir, however, will not exceed the user-spec-ified maximum down stream release rate (normally equal to the maxi-mum non-damaging release rate). Furthermore, if a downstream remote control node is defined, the model will attempt to regulate the release in order to keep the river flow rate at the control node under the user-defined maximum flow rate. In a disaster situation (spill over the top of the dam) is there no limit on the flow rate.

9.4 Spillways

Releases during flood control operations can be controlled by two spill-ways: a (top) spillway defined by the hydraulic capacity, the Spill Capac-ity table Q(h) and its bottom level, the Spillway Bottom Level time series, and a second spillway, defined by the Bottom Outlet Capacity time series Qb(t), often assumed located at the base of the dam.

The Spill Capacity table is optional for both regular reservoirs and lakes. The Spillway Bottom Level time series and the Bottom Outlet Capacity time series apply to true reservoirs only.

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Spillways

If they exist in a particular dam, both are generally used for flood control operations. The spillway capacity is generally determined physically by water level (relative to the spillway base), and must thus be given as an h-Q(h) table. The bottom outlet's capacity, on the other hand, can usually be regulated, and thus must be given as a time series.

Spillway limitations can cause the water level in the reservoir to rise above flood control level and even above the Crest Level of the dam. The spillway properties is specified in the spillway tab. Other properties, which may directly influence how the spillways work are the Flood Con-trol Level (FCL) and the Maximum Release Limit.

Spill Capacity table (optional) Spillway Capacity Table is an h-Q table, where h is water level relative (above) to the Spillway Bottom Level and Q(h) is maximum possible release (volume/time) at that water level. The operating for the top spill-way is between the Spillway Bottom Level time series and Crest Level.

The release through the spill way is the maximum of Q(H) and the Maxi-mum Release if the later is specified in the Operation Rules dialog.

Spillway Bottom Level time series (optional)Spillway Bottom Level time series describes the base level of the spillway to which the relative value given in the h-Q relationship above refers to. The Spillway Bottom Level can be either above, below or at FCL.

If this time series is not specified, the Spill Capacity table will use the FCL as the basel level above which the releative water level h in the h-Q(h) table refers to.

Bottom Outlet Capacity time series (optional) Bottom Outlet Capacity is a capacity limitation time series Q(t). It is designed to release/flush water from the lower part of the reservoir, when the water level is higher than the FCL. The operating range for the Bottom Outlet spillway is between Flood Control Level and Crest Level.

If the Spillway Bottom Level time series is not specified the Bottom Out-let Capacity time series will be set to zero.

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Reservoirs

Both spillways may function simultaneously if the level in the reservoir exceeds both the FCL and the spillway bottom level. If a Minimum Release Requirement time series has been specified in the operation rules, this will be added to the above.

If the release from the Bottom Outlet Spillway shall include the Minimum Release requirements at times when the water level in the reservoir is above the FCL, then the Minimum Release Requirement time series should be subtracted from the Bottom Outlet Capacity time series Qb(t).

Similar, if the release through the top spillway should include the Mini-mum Release Requirement at times when the flow is above the Spillway Bottom level, then the h-Q(h) relationship should be corrected according to the the Minimum Release Requirement.

Illustrating how the spillway worksThis example illustrates how the spillway functions work in a situation where the reservoir is emptied, and no inflow occur. The initial water level is 543 m, Flood Control Level (FCL) is 542 m. The Bottom of Spillway is 541 m, and the Bottom Outlet Spillway capacity is 1.5 m3/s.

The figures below show that the release through the spilways is the sum of spillway capacity (the Q(h) curve) plus the Bottom Outlet Spillway capac-ity = 1.5 m3/s from initial water level down to FCL. The release between FCL and the Bottom of Spillway level (=541 m) follows the spillway q(H) curve as the release from the Bottom Outlet Spillway is zero.

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Water Quality

9.5 Water Quality

Like reaches, reservoirs can have a significant residence time, which has to be taken in account with water quality modeling.

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Reservoirs

In the tab, the default choice is to assume conservative transport. When you uncheck that option, you can make further choices.

The Parameter Set input indicates the reaction parameters essentially the same as for reaches. See Water Quality (p. 55)The only reservoir-specific parameter is the Vollenweider coefficient. You can still use the same parameter set for reaches and reservoirs, as long as you fill in both reser-voir and reach-specific parameters in the respective dialogs.

The initial state, like in groundwater, can be either pristine or steady state. Pristine means zero concentrations except for DO, which is set to its satu-rated value for the current temperature. At steady state, concentrations in the inflow from the upstream reach equal those in the reservoir, thus the reservoir concentrations are set to those calculated for the first time step in the reach upstream of the reservoir.

108 MIKE BASIN

10 HYDROPOWER Hydropower generation is simulated by inserting a hydropower node and connect it to a reservoir using the channel feature. Return flow back to the river is simulated by connecting the hydropower node to the first down-stream river node.

Plant characteristics are described in the hydropower properties dialog below.

.Important attributes describing the hydropower plant are:

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Hydropower

Power Demand Time seriesThe time series file contains the following items ((See the fly by text of the Use Filter option to see valid data types):

Target power demand (either as Target Power [MW or equivalent] or as Water Flow [m^3/s or equivalent]

Installed capacity (effective only when 'use surplus capacity' is checked in the hydropower dialog, but must always be present and non-blank

Surplus capacity Usage [dimensionless]. Fraction between 0 and 1.

Minimum head for operation of turbines. If head (difference between reservoir level and tailwater level) drops below this threshold, no water is routed through the turbines, regardless of power demand

There is an option to produce more power than demanded (up to installed engine capacity) at times where there is a surplus of water in the reservoir. When the reservoir water level is above flood control level, water that would otherwise be spilled can be routed through the turbines. Any release that - due to limiting turbine capacity - cannot be exploited for hydro-power generation is spilled from the reservoir.

Use Minimum release from reservoir optionIf minimum release is specified in the reservoir, this water can be routed through the hydropower node.

In the old MIKE BASIN, the minimum release was top-added to the hydropower demand, which means the extra water is routed throught the hydropower. If you would like to use this method, change the MIKE BASIN options as described in Options... (p. 18)

Tailwater table (optional)This table specifies tail water elevation as a function of release from the reservoir. Note that a discharge-dependent tail water level necessitates iterations in the solution of the water allocation problem (demand becomes a function of tail water level, which depends on reservoir release, which finally depends on demand). Thus, for precise results, often a daily simulation time step should be chosen in connection with hydropower simulations.

Engine efficiency table (optional)This table specifies turbine/machine efficiency as a function of head dif-ference or the discharge. Note that a head-dependent or discharge depend-ent efficiency necessitates iterations in the solution of the water allocation

110 MIKE BASIN

Hydropower - Formula

problem (demand becomes a function of efficiency, which itself depends on reservoir level, which again depends on reservoir release, which finally depends on demand). Thus, for precise results, a daily or shorter simula-tion time step should be chosen when the machine efficiency table is used.

Backwater effects In cascades of reservoirs, tailwater elevation for a hydropower station can be determined by water level in the next reservoir downstream rather than by discharge from the supplying (upstream) reservoir. If you know this to be the case for a particular model, check the "backwater" option.

Head ApproximationCalculation of hydropower demands and actual generation is subject to numerical inaccuracy when tailwater and/or power efficiency tables are used. There are two approximations available

an explicit method based on head in the supplying reservoir at the start of the time step, or

a time step average method based on the average head at start and end of the time step.

10.1 Hydropower - Formula

MIKE BASIN calculates the hydroelectric effect produced from the fol-lowing formula:

(10.1)

where P is the power generated, ∆h is the effective head (difference) [L], Q is the discharge/release through turbine(s) [L3/T], ε is the machine effi-ciency [-], and g is the gravitational constant [L/T2]:

or from

(10.2)

where θ is the density of water [M/L3].

The effective head difference is:

(10.3)

P ∆h Q( ) Q ε ∆h( ) g ρwater⋅ ⋅ ⋅ ⋅=

P Q ε Q( ) g p⋅ ⋅ ⋅=

∆h Q( ) hreservoir htailwater Q( )– ∆hconveyance Q( )–=

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Hydropower

The hydropower formula is non-linear because of the dependencies of head difference on discharge and machine efficiency. Tailwater levels are generally a function of discharge, and so are additional conveyance head losses in the channel (both increase with discharge)., see the Channel Properties Dialog In addition the tailwater can also become governed by backwater from the reservoir downstream rather than discharge of the sup-plying reservoir. In the simulations, the applicable tailwater level for use in equation (10.3) is found as

(10.4)

In MIKE BASIN, the following inter-dependencies between variables can be assumed constant or insignificant by leaving out the respective detailed specifications:

htailwater(Q): = hreservoir_buttom_level (leaving out the tail water table)∆hconveyance: = 0 (leaving out the conveyance head loss

table)ε(∆h): = 0.86 (leaving out the power efficiency table)

Water demand for power generation is calculated by solving the power formula, equation ( 1 ), for Q (the solution must be found iteratively). When the effective head difference is small, turbines are however shut off, both because they are inefficient and because the required discharge would grows very large. Accordingly, a minimum head for operation hmin can also be specified in MIKE BASIN. If h < hmin, Q is set to zero, i.e., no water is routed through the turbines, regardless of demand.

htailwater max htailwater Q( ),hdownstream_reservoir( )=

112 MIKE BASIN

Overview

11 IRRIGATION

11.1 Overview

An irrigation node represents an irrigation area comprising one or more irrigated fields, which are drawing water from the same source(s). The irrigation node represents the total irrigation demand for the fields, and optionally the crop yield.

Based on the calculated demand, water is extracted from one or more sources, e.g. river nodes and/or reservoirs according to specified alloca-tion rules. An irrigation node may also extract groundwater. Any excess water may be returned to the river system through surface water channels.

In a river basin model, the irrigation nodes functions very similar to the water user nodes, the main difference being that the ordinary water user works on prescribed demands and return flows, whereas the irrigation node calculates the two variables dynamically. Allocation rules that are available for other water user nodes also apply to irrigation nodes.

Figure 11.1 The irrigation node schematisation

In each time step the following computations are carried out by the irriga-tion node:

Calculation of the total crop water demand. The crop water demand depends on the local climate and the crops growing in the fields. Note: It is assumed that the all fields represented by an Irrigation Node use the same climate and reference evapotranspiration data.

Calculation of the irrigation demand. The irrigation demand may be different from the total crop water demand, as it depends on the irriga-tion strategy and soil type in a field. Losses in the connection channels (seepage or evaporation) as well as surface runoff are taken into account in the irrigation demand as well.

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Withdrawal of water from the sources. Once the total demand has been calculated for the irrigation node, water is exstracted from the sources according to the same allocation rules that applies to the irriga-tion node.

Distribution of water among the fields. If irrigation demands are met, the source water is distributed among the fields according to their demands. If there is insufficient water to fulfil the demands, a number of deficit management rules can be chosen to define the distribution of water to the individual fields.

Return Flows. Only runoff generated by the runoff sub-models will be returned to the river network through connection channels. All other losses should be included as evaporation/seepage in the connection channels.

Crop Yield. Finally, when the irrigation depth for each field has been calculated, the crop yield is calculated (optional).

11.2 Node and sub-model relationship

Each Irrigation node represents a number of fields. These fields need to be defined for the irrigation node. However, several fields across the basin can have similar characteristics, e.g. data for soils or crop sequence. To minimize the number of parameters that needs to be defined for each irrigation node, the properties of individual fields are specified independ-ently of the irrigation node and stored as separate parameter sets. These parameter sets are referred to as sub-models in the following.

At the irrigation node level only one climate sub-model and one reference ET sub-model represents all the fields within the irrigation area covered by the node. At the field level, sub-models for soil characteristics, runoff characteristics (optional), and a crop sequences /water managment should be given.

A crop sequence defines a sequence of Crop/Irrigation sub-model pairs (e.g. Wheat/Sprinkler - Maize/Sprinkler - Grass/No Irrigation). Option-ally, the cropsub-model mayinclude a yield model.

All the sub models are defined in the Irrigation data.. forms, which are accessed from the MIKE BASIN drop-down menu.

Once the sub-models are defined, they can be accessed from the irrigation node property menu. Important: This Node - Sub model relationship

114 MIKE BASIN

Node and sub-model relationship

implies that normally, the way to setup an Irrigation Node would be to start by defining the required sub-models, and then adding the Irrigation node and make the references to the sub-models from the Irrigation Node Properties dialog.

11.2.1 Editing sub-model menusAll sub-model data forms are empty when new projects are created.

When clicking the "New" button, a new sub-model with a default name is created. The name can be changed by typing directly in the name field of the Model Picker. The appearance of the sub-model menu depends not only on the selected sub-model, but also on the sub-model type, which may be available. The type of the sub-model is selected in the Model Type Picker. Whenever the model type is changed, the menu will change accordingly.

Example: The sub-model type for Reference Evapotranspiration may be of the type Time series, or FAO 56.

Note: The sub-model type, which has been specified at the time the menu is closed will be used whenever there is a referrence to the sub-model.

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11.3 The Irrigation Node

The irrigation node is added to the model by clicking the "Add Irrigation Node" tool in the MIKE BASIN toolbar, and digitizing in the map view. Connections to the river network are added with the "Add channel" tool.

The Irrigation Node Properties dialog is shown below.

11.3.1 Scheme

The dialog contains three tabs. The main tab (Scheme) is where the fields are defined. The remaining two tabs are related to the specification of water allocation rules, and are identical to the ones available in regular water users, with the exception of return flow rules. For the irrigation node, the return flow fraction is applied to the actual return flow rate and not to the demand as for regular users.

Important: This implies that the return flow fractions for Irrigation Nodes should sum up to 1.0.

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The Irrigation Node

In the top of the Fields tab, the name and category of the Irrigation node may be defined. Below that, the climate and reference ET model to be used for the current node is selected from the collection of sub-mod-els..When a sub-model has been selected in the pull-down menu of the sub-model picker, the ID and model type is shown.

Deficit distribution methodsDeficit distribution methods are used when the irrigation demand exceeds the available water at the sources. In such cases, the deficit distribution methods describe how the available water should be distributed among the fields represented by the node. Three options are available.

Equal shortageThe fields get the same percentage of the demand covered, and hence suf-fer the same relative shortage.

By yield stressThe water is distributed according to how sensitive the crops are to soil water stress at the time of water shortage. This implies that the crop with the highest yield response factor (Ky) will be given the highest priority. In case of several crops with the same yield response factor, water is distrib-uted among these fields according to the equal shortage method.

By priorityThe water is distributed according to the priority that has been specified for the field. The fields with the highest priority will receive the full demand first. If several fields have the same priority, water is distributed according to the equal shortage method.

When the deficit distribution method has been selected, the fields that are represented by the node need to be defined.

FieldsA field is defined by a name, its area, the sequence of crops growing in it during the simulation period, the properties of the soil in the field and optionally, its ability to generate runoff. A field is added to the Irrigation Node by clicking the "Add Field" button, which results in a line being added to the fields table in the Fields tab. The properties of the field may be edited directly in the table, or by selecting the row of a field, and click-ing the "Edit Field" button. The latter approach will result in a Field dialog being opened.

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The field name, area and priority are defined in the top of the form. More-over, a so-called minimum cycle time has to be specified. This is impor-tant, if the farmer cannot irrigate the whole field within a single time step.

Example: If it for instance takes him two days to irrigate the entire field and the time step is one day, then the field is divided into two field sec-tions and one the first day he irrigates one half and the next day the other half.

Hence, soil moisture, and consequently yield, may be different on the two field sections and internally these are treated as two fields. In each output time step, the average field conditions are written to the result file. To dis-able the minimum cycle time, set it to a value less than the simulation time step.

Finally, a crop sequence and a soil water model are selected from the col-lection of sub-models (see the next section) with the corresponding sub-model pickers. Optionally, a runoff model may be selected.

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The Irrigation Node

11.3.2 Surface Water

Priority of upstream supply nodesWhen the irrigation node is linked to mulitiple upstream river nodes, you can edit the water extraction rules from different nodes.

Call by priority. Water is extracted from upstream nodes to satisfy the demand in the order of priority beginning with nodes having the lowest priority number.

Call by fraction of demand. Water is extracted from each upstream node based on the fraction of the demand required from each node. If an upstream node cannot fulfil its fraction there is no attempt to extract water from another upstream node.

Return flow rule(s)The return flow rule fields will automatically be filled with a number of downstream nodes corresponding to the number of downstream return flow nodes from the water user node.The time series to be specified must contain the return flow fraction for each downstream node.

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11.3.3 Groundwater

An irrigation node can intake the water from the groundwater source.

Three different options are available for using groundwater. Refer tothe description in Groundwater (p. 84)

Supplying CatchmentYou can specify the catchment from which the groundwater is taken.

11.4 Sub-Model Overview

The available sub-models are described in the sections below.

11.4.1 The Climate Sub-ModelThe climate sub-models available accept a number of commonly available climate inputs, and convert them to the input required by the Reference ET model and Precipitation. Two model types are currently available:

Rainfall OnlyThis is the simplest climate model, and the only required input is a time series containing rainfall.

If rainfall is provided on a low temporal resolution (e.g. monthly data), functionality to disaggregate the data into a higher temporal resolution is provided. By checking the "Disaggregate Rainfall" checkbox, a field where an aggregation period can be set becomes enabled. Setting the time span to e.g. 10 days results in a rain event every 10 days, of a magnitude that corresponds to:

Rain depth = (aggregation period) / (Input time step) * (Rainfall depth for input time step)

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Sub-Model Overview

The FAO 56 Climate modelThe FAO56 model type accepts the climate input required for the calcula-tion of the FAO56 Reference Evapotranspiration. Hence, this method is only relevant if the Evapotranspiration sub-model is of the type FAO56. The required input is: Relative Humidity, air temperature (max and min), wind speed and sunshine hours. Moreover, rainfall data is required.

Disaggregation of rainfall is provided for the FAO56 climate model as well.

11.4.2 Reference EvapotranspirationThe Reference ET sub-model is responsible for providing the Crop sub-model with reference evapotranspiration in each time step of the simula-tion. The evapotranspiration rates may either be calculated based on the input from the Climate Sub-model, or provided directly as time series. Two types of the Reference ET sub-model are currently available.

FAO56 Reference ETThe FAO56 model uses the standardized Penman-Monteith equation for calculating reference evapotranspiration. This method can only be used in combination with the FAO56 Climate Model. The FAO56 reference ET model requires no additional input.

The reference ET is calculated as:

where :

: reference evapotranspiration [mm day-1],

: net radiation at the crop surface [MJ m-2 day-1],

: soil heat flux density [MJ m-2 day-1],

: air temperature at 2 m height [°C],

: wind speed at 2 m height [m s-1],

: saturation vapour pressure [kPa],

ET0

0,408∆ Rn G–( ) γ 900T 273+------------------u2 es ea–( )+

∆ γ 1 0,34u2+( )+---------------------------------------------------------------------------------------------=

ET0

Rn

G

T

u2

es

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Irrigation

: actual vapour pressure [kPa],

: saturation vapour pressure deficit [kPa],

slope vapour pressure curve [kPa °C-1],

psychrometric constant [kPa °C-1].

The FAO Penman-Monteith equation provides the evapotranspiration from a hypothetical grass reference surface and provides a standard to which evapotranspiration in different periods of the year or in other regions can be compared and to which the evapotranspiration from other crops can be related.

A detailed description of the calculation procedure for the Penman-Mon-teith formulation is described in FAO56, and contains the following calcu-lation steps:

Derivation of all required climatic parameters from the daily maximum (Tmax) and minimum (Tmin) air temperature, altitude (z), mean wind speed (u2) and geographical location.

Calculation of the vapour pressure deficit (es - ea). The saturation vapour pressure (es) is derived from the mean temperature, which is assumed to be the average of Tmax and Tmin. The actual vapour pres-sure (ea) is be derived from the minimum temperature, which is assumed to equal the dew-point temperature

Determination of the net radiation (Rn) as the difference between the net-shortwave radiation (Rns) and the net long-wave radiation (Rnl). These variables are derived from geographical location, sunshine hours and vapour pressure. The effect of soil heat flux (G) is ignored for time steps smaller than 10 days as the magnitude of the flux in this case is relatively small.

ETo is obtained by combining the results of the previous steps.

Time seriesAs an alternative to the FAO 56 calculation of reference ET, this model type accepts time series of reference evapotranspiration. This method works with the less data requiring "Rainfall Only" climate model type.

11.4.3 Soil Water ModelThe main task of the soil water model is to keep track of the amount of soil water available for soil evaporation and crop evapotranspiration at any time during the simulation. The soil water content may also be used by the

ea

es ea–

∆

γ

122 MIKE BASIN

Sub-Model Overview

Irrigation sub-model to determine the irrigation demand. A single soil Water Model is currently available.

FAO 56 Soil Water ModelThe FAO56 Soil Water Model is a simple water balance based model that follows the recommendations provided in FAO56 for use with the dual crop coefficient method. It keeps track of the soil moisture content in a surface storage from where soil evaporation can take place, and a root zone storage that provides water for transpiration. The depth of the surface storage is specified as the "Depth of evaporable layer" and the depth of the root zone equals the root depth at any time during the simulation.

It is assumed that the evaporable layer drains to the root zone when field capacity is reached. The wetting fraction (equals 1.0 for rain and is user specified for irrigation) is taken into account when the exchange between the evaporable layer and the root zone is calculated, and hence for wetting fractions less than 1, water may be exchanged for average water contents in the evaporable less than field capacity.

Runoff ModelThe task of the runoff model is to calculate the fraction of the precipitation that will leave the field as surface runoff, and hence never enter the root zone. If the Irrigation Node is connected to the river network, surface run-off will enter the connection channel.

Specification of a runoff model is optional. If no model is selected in the field, the runoff is assumed to be zero. A single model is currently availa-ble.

Linear runoffThe linear run off model assumes a linear relationship between the rainfall intensity and the amount of surface runoff.

Regardless of the specified parameters, the runoff will never be negative.

11.4.4 Irrigation ModelThe irrigation sub-models is used to specify how and when a given field is irrigated. A single irrigation model type is available.

FAO 56 Irrigation ModelThe irrigation model requires a wetting fraction that determines the frac-tion of the field surface that is being wetted during irrigation. For e.g.

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sprinkler irrigation this fraction will be close to 1, whereas for drip irriga-tion it may be as low as 0.1. The wetting fraction is also an important fac-tor for how much irrigation is required before the surface soil storage is filled and hence when the root zone starts to fill.

Specification of a spray loss is required as well. The spray loss is the frac-tion of the irrigation water that is evaporated before the water reaches the soil surface. For sprinkler irrigation, this fraction may be relatively high, whereas it is relatively low for e.g. drip irrigation.

The Trigger option determines when the irrigation will start. There are three options available:

Fraction of Total Available Water (TAW): Irrigation starts when the soil moisture content reaches the specified fraction of TAW. TAW is defined as the volume of water contained in the root zone when at field capacity.

Fraction of Readily Available Water (RAW): Irrigation starts when the soil moisture content reaches the specified fraction of RAW. RAW is defined as the volume of water that can be transpired by the crop with-out exposing the crop to soil water stress. It is defined as RAW = (1 - p) x TAW, where p is related to the crop (see the Crop Model section).

Specified depletion depth: Irrigation will start when the soil moisture content reaches the specified depletion.

When the irrigation has started the application depth is calculated accord-ing to the Application Option. Three options are available:

Fraction of Total Available Water (TAW): Irrigation stops when the soil moisture content reaches the specified fraction of TAW.

Fraction of Readily Available Water (RAW): Irrigation stops when the soil moisture content reaches the specified fraction of RAW.

Fixed depth. The specified depth of water is applied to the field.

11.4.5 Crop ModelGiven the soil moisture content and reference evapotranspiration, the crop model is responsible for calculating the corresponding crop evapotranspi-ration and soil evaporation. A single model is currently available.

Dual crop coefficient model (FAO56) The FAO56 method is based on the dual crop coefficient method described in FAO56. The dual crop coefficient model calculates the tran-spiration and soil evaporation separately and thus allows for a more accu-

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Sub-Model Overview

rate quantification of the consequences of using different irrigation technologies.

Following the FAO56 terms the crop stages are divided into an initial, development, middle and late crop stage. Each stage is assigned a length. For each stage, a so-called basal crop coefficient (Kcb) is assigned. The basal crop coefficient is defined as the ratio of the crop evapotranspiration over the reference evapotranspiration (ETc/ET0) when the soil surface is dry but transpiration is occurring at potential rate.

Kcb is assumed constant in the initial and middle stages, and assumed to follow a linear variation between the stages.

The root depth determines the maximum depth from which the crop can extract water, and the minimum and maximum depth has to be specified. It is assumed that the maximum depth is obtained at the beginning of the middle stage, and that the variation between the initial depth and the max-imum depth is determined by the following relationship:

Where:

Kcb,ini:Initial crop basal coefficient

Kcb,mid:Crop basal coefficient in middle stage

Rmax:Maximum root depth

Rmin:Minimum root depth

The influence of the surface roughness on the evapotranspiration is taken into account through a climatic correction factor applied to the basal crop coefficient. The vegetation height is assumed to scale with the basal crop coefficients and is calculated as

for the initial and development stage, after which the height is assumed to have reached its maximum ( )

Finally, a so-called p-value needs to be specified. The p-factor expresses the sensitivity of the crop to soil moisture stress, or more specifically, the fraction of the totally available water (TAW) at which soil moisture stress will start to reduce crop transpiration. The amount of water that may be depleted without stressing the plant is called the readily available water (RAW). The relationship between RAW and TAW is:

R = (Kcb – Kcb,ini)/(Kcb,mid – Kcb,ini) * (RMAX – RMIN) + RMIN

H Kcb Kcb ini,–( ) Kcb mid, Kcb ini,–( )⁄ Hmax⋅=

Hmax

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For soil moisture contents below RAW, transpiration is assumed to decrease linearly with soil moisture content and reach zero when the wilt-ing point is reached.

A yield model may be attached to the crop model by selecting an appropri-ate model with the yield model selection control.

11.4.6 Yield ModelAttaching a yield model to a crop model makes it possible to convert a soil water stress into the corresponding yield loss, and hence to quantify the costs of a soil moisture deficit. A single yield model is currently available.

FAO 33 Yield ModelThis model is based on a so-called potential yield (Yp), which is the crop yield under optimal conditions (no soil moisture stress). The sensitivity of a crop to soil moisture stress depends on the growth stage. A crop will usually be more sensitive to soil moisture stress in an early stage than in a late growth stage. This is taken into account with a Yield Response Factor (Ky). A yield response factor has to be specified for each of four growth stages. Each stage is assigned a length that may, but does not have to, be the same as the growth stages in the Crop Model to which it is assigned.

The crop yield is calculates as:

where Ya is the actual yield, Yp is the potential yield, is the actual transpiration and is the potential transpiration. Index is the i´th growth stage in a growing season with a total of growth periods.

11.4.7 Crop SequenceA crop sequence is really not a sub-model in the sense that it is just a con-venient way of specifying how a field is managed. However, since the same crop sequence may be used in several fields, it makes sense to keep the crop sequence dialogs with the sub-models.

A crop sequence consists of a sequence of crop shifts. A crop shift is char-acterised by a starting data (sowing data), a crop, and optionally a refer-ence to the irrigation sub-model that will be used to irrigate the crop. A crop shift lasts until the end of the last growth stage of the crop in the field.

Ya

Yp----- 1 Kyi 1

Eta

Etp--------–

–i 1=

i G=

∏=

EtaEtp i

G

126 MIKE BASIN

Simulation output

If a crop is harvested before the next crop is planted, the model assumes that there are no crops at this field in the time between crops, and hence that the irrigation demand is zero. When the next crop is sowed the water content in the root zone will be reset to the initial water content, as speci-fied in the soil water model.

11.5 Simulation output

The most general output items for the Irrigation Node is written to the MIKE BASIN output files, and imported into ArcGIS, just like the output from the remaining MIKE BASIN model building blocks.

However, for each Irrigation Node, an additional output file, containing detailed information about each field, is. The additional files are written to the working directory for the MIKE BASIN project. The file names are used to identify the relationship with the Irrigation Nodes in the model. The file names are of the form: IrrigationNodeName_ID_XX.dfs0, where IrrigationNodeName is the name that has been assigned to a node in the properties dialog, and XX refers to the SchemeID of the Irrigation Node.

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128 MIKE BASIN

The Classic Symbology option (default)

12 FEATURE SYMBOLOGYEach MIKE BASIN building block is represented by distinct symbols on the map display. The default symbol for a Water User node is a brown house icon, a reservoir is represented by a blue triangle, the catchments are shown as semi-transparent green polygons, hydropower nodes are blue circles with a yellow lightning inside, and river reaches and connection channels are represented by blue and black lines, respectively.

These symbols may, however, all be changed according to specific project needs and preferences of the modeler. Two symbology options are cur-rently available, the Classic Symbology (default), and the Advanced Sym-bology option. It is possible to switch between the two options under the Symbology tab in the Options dialog which is accessed in the MIKE BASIN drop-down menu.

Figure 12.1 The symbology tab in the MIKE BASIN Options dialog

12.1 The Classic Symbology option (default)

When a new MIKE BASIN project is created, or when a project created in a previous version of MIKE BASIN is opened, MIKE BASIN will start up in Classic Symbology mode. In Classic Symbology mode each MIKE BASIN building block is represented by a single, distinct symbol.

To change the symbol for a given building block, double-click on the sym-bol in the ArcGIS Table of Content (TOC), and select one of the prede-fined symbols in the ArcGIS Symbol Selector. Alternatively, the ArcGIS Symbol Property Editor can be used to create advanced, customized sym-

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Feature Symbology

bols. The ArcGIS Symbol Property Editor is opened by clicking the "Properties…" button in the ArcGIS Symbol Selector Dialog. When the new symbol has been selected or created, the symbol of all existing fea-tures of the given type will change accordingly.

12.2 The Advanced Symbology option

In some cases it will be useful to be able to distinguish visually between different sub-categories of the same building block. For example a Water User node may represent a City, Industry or any other water consumer. A river reach could be categorized as a main river or tributary, and reservoirs may be categorized according to e.g. size. With the Advanced Symbology option, the category of a feature can be taken into account when the fea-ture symbology is created.

A category can be assigned to all MIKE BASIN features in the Category field in the Properties Dialog of any given feature. If no category has been specified for a feature it will be represented by the default symbol in the map

Figure 12.2 The Category field in the Properties dialog

New categories are defined by typing in the Category field, and existing categories can be selected in the drop down list. When a new category is defined for a feature, this category will be available as an existing cate-gory in the category drop-down list for all other features of the same type.

MIKE BASIN will detect any new categories when a property form is closed, and ask if the symbology should be updated. If so, a new symbol will be added to the MIKE BASIN symbology.

The default symbol for new category of a given building block will be the default symbol for the building block with a slightly modified color. The symbols may be changed using the ArcGIS Symbol selector or ArcGIS Symbol Property Editor.

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The Advanced Symbology option

When in Advanced Symbology mode, two buttons becomes enabled in the MIKE BASIN Options form. The Rebuild Symbology button rebuilds the entire symbology with default symbols. All customized symbols will be replaced. The Update Symbology button will look through the entire list of defined categories and add any missing categories to the symbology, without changing the customized symbols that may already have been defined.

IMPORTANT: The ArcGIS symbology is stored in the mxd file. There-fore, make sure to save the mxd file when before closing a project. The fact that the symbology information is stored in the mxd also implies that the symbology has to be recreated when a new project, based on an exist-ing database is created.

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Feature Symbology

132 MIKE BASIN

13 RESULT PRESENTATIONThe simulation output of MIKE BASIN can be presented in several ways.

"Plotting of time series

"Statistical summaries of time series presented in maps and/or reports

"Animated maps

Most of the result presentation functionality can be accessed through the "MIKE BASIN Results" toolbar in ArcGIS

Figure 13.1 The MIKE BASIN Results toolbar

Time series plottingProbably the most common way of accessing simulation results is to plot the result time series of the item of interest directly. The easiest way to find a result item is to right-click on the MIKE BASIN feature of interest and selecting "Time Series…". This will open a dialog that contains a list of all time series that are associated to that particular feature, and hence both input time series and result time series will be present in the list.

An example of the time series dialog and a time series plot is shown below.

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Result presentation

Figure 13.2 Example of the time series result dialog.

Result time series will be prefixed by the simulation name. When a time series is selected in the list, time series details will be shown in the Time Series Details view. The buttons in the right hand side of the form pro-vides access to the most common time series operations, such as plotting, statistics, export and finally a button to add the selected time series to the Time Series Analysis window. Please consult the Temporal Analyst man-ual for detailed information regarding this.

Statistical summaries in maps and reportsVery often a statistical summary of a time series is more useful than the time series itself, especially when the results from a large number of fea-tures needs to be presented. Examples of such common statistical summa-ries are the time weighed average, maximum and minimum values. However, more advanced summaries such as event statistics, ramp statis-tics, trend statistics, within-period extremes and quantiles may provide even more valuable insight than what could be obtained from the raw time series plots.

134 MIKE BASIN

MIKE BASIN Result Presentation Wizard

Common for both the simple and the more advanced statistical summaries is that they are well suited for presentation in maps, graphs and reports.

This section describes how to get from the raw result time series produced during a MIKE BASIN simulation to advanced map presentations, graphs and reports.

For all options, the first step is to run the scenarios for which the results should be presented, and make sure that the results are associated to the MIKE BASIN features. Next, the MIKE BASIN Result Presentation Wiz-ard is opened.

The purpose of the wizard is to help the user to convert the raw result time series into statistical summaries that is stored in a result feature class. Once the results are structured in a feature class, the existing ArcGIS func-tionality may be used to present it as maps and graphs, and the built-in ArcGIS Report Wizard or Crystal reports can be used to create full feare-tured reports that may either be printed or published to the web

13.1 MIKE BASIN Result Presentation Wizard

Step 1 of the Result Presentation Wizard is shown below.

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Result presentation

The Result Presentation Wizard works on a set of results that are all asso-ciated to a single MIKE BASIN feature type (e.g. water users, reaches or catchments). To select the feature type for which results should be proc-essed, set the Feature Class (Nodes, Reaches or Catchments), and Feature Type using the pull-down menus.

If results are to be produced for a subset of the features of the selected type only, the features may be filtered by category. After selecting the Feature Type, the Category pull-down menu will contain a list of the categories that has been defined for the selected feature type. To limit the result processing to a single category, select the one of interest. To produce results for all categories, select <All>.

The results may all come from the same simulation, or results from multi-ple simulations may be processed simultaneously, which is useful when results from different simulations need to be compared. The simulations that contain results for the features of the selected type and category are listed in the "Available Simulations" list. Move the simulations of interest to the "Selected Simulations" window by double clicking the simulation or by using the arrow buttons.

A click on the Next button progresses the form to step 2, Spatial Sum-mary.

136 MIKE BASIN


Step 2 is optional, and only relevant if the results from several features need to be summarized over larger areas.

Example: If the user wants to calculate the total volume of used water and total deficit for all users inside an arbitrary polygon layer (e.g. the MIKE BASIN catchment layer, or a municipality layer), the functionality in step 2 needs to be enabled.

The polygon layer that the results should be aggregated to is selected in the Aggregation Layer drop-down list. Only layer that are visible in the ArcGIS TOC can be selected.

The settings under "Spatial Summary Settings" determine how the results should be aggregated to the polygon layer. Six options are available, and results will be calculated for each selected option. At least one option has to be checked.

Example: For the "Used Water" result item, it would make sense to select the "Sum" option, whereas for groundwater levels, the "Average", "Min", or "Max" options would be the appropriate choices.

If <All> has been selected in the Category drop-down list in Step 1, the functionality in Summary by Category group becomes enabled. This allows to summarize all categories into one result (default), or to make

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Result presentation

separate summaries for each category. The latter is relevant if results from the different categories need to be compared.

Example: If the only result of interest is the total volume of water used by all water users in the aggregation layer (regardless of category), the "Sum-marize all categories in one result" should be selected.

Example: If the total used water from Water Users with different catego-ries (e.g. Cities, Livestock and Industry) later needs to be compared in e.g. pie plots, the "Make separate summaries for each category" option needs to be enabled.

A click on the Next button takes the user to Step 3, Layer Composition. As the name indicates, this is the step where the actual content of the feature class produced by the wizard is defined.

Each result feature class can be identified by the name provided in the Result Name box, and since many different result feature classes may co-exist in the same GeoDatabase, the name has to be unique.

The 'Add Item' and 'Remove' link buttons are used to add result items to the list. When the 'Add item' button is clicked, a new dialog opens.

138 MIKE BASIN


In the 'Add Layer Item' dialog, the result item is defined. Each item has to have a name that describes it. The name will later be used to identify the result item in the feature class table.

In the Result Item drop-down list, the stored result types are listed, and this is where the subject of the analysis is selected.

The time period for which the analysis can be performed can either be an absolute period, or a relative period (e.g. May to October, every Tuesday or every day between 8 a.m. and 8 p.m).

The actual operation needed to get from the raw time series to the desired statistical summary is selected in the Operations group. For details regard-ing the different statistics, the user is referred to the Temporal Analyst manual (Evaluate to scalar section).

When the 'Add to Layer' button is clicked, the results will be processed and the result item is added to the feature class composition. The item will be represented by the provided name, extended by the simulation that is being analyzed. If more than one simulation was selected in Step 1, a cor-responding number of result items will be created in the composition each time a new result item is defined.

Finally, when all desired result items has been added to the composition, the 'Next' button in step 3 takes the user to a summary sheet, and finally,

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Result presentation

when 'finish' is clicked, the results are created in a GIS feature class, and each result item is displayer with a default symbology in the ArcGIS table of content. Each field in the feature class table will be added to the ArcGIS table of content as a layer with a default symbology. All result layers will be located in a group Layer named "Result Presentation".

13.2 Result Manager

A list of MIKE BASIN result feature classes that are available in the project database at any given time can be obtained with the Layer Man-ager that is accessed through the MIKE BASIN Result Presentation tool-bar. From this dialog it is also possible to delete obsolete result feature classes.

Presenting data in the Result feature classesFrom the point where the results have been summarized in MIKE BASIN Result Feature classes, the standard ArcGIS symbology functionality as well as graphing and reporting features can be used to create sophisticated presentations.

First of all, the default symbology may be changed to used some of the more advanced ArcGIS build-in symbology options such as Quantiles (Graduated symbols, Graduated colors and Proportional symbols), or Charts (Pie, Bar/Column and Stacked). The ArcGIS build in Symbology

140 MIKE BASIN

Animated maps

options are accessed by right-clicking the Layer name, selecting Proper-ties in the context menu, and the select the Symbology tab.

The result feature classes may also be converted by using the ArcGIS built-in Graph functionality which can be opened through the MIKE BASIN Results toolbar (see Figure 13.1).

Finally, the Result feature classes may for the basis for sophisticated reports that may be created either with the build-in ESRI Report tool, or with Crystal Report. Both report tools can be accessed through the MIKE BASIN Results toolbar.

Examples that illustrates how to get from the result feature classes to full featured presentations are available for download on the MIKE BASIN homepage (www.MikeBasin.com)

13.3 Animated maps

The first step in creating an animation is to create a Result Group Defini-tion that contains the results that should be included in the animation. Results groups are created with the MIKE BASIN Result Group Editor (reference to Result Group chapter). Only one result item for each MIKE BASIN building block can be included in an animation, and hence only one result type should be included in the result group for each MIKE BASIN building block.

Example: Used water and Water Demand deficit may not both be present in the Water Users part of the result group.

Next, run a simulation with the result group created for the animation.

Clicking the Animation button in the MIKE BASIN Results toolbar will open the Animation dialog (below).

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Result presentation

Here, the animation is assigned a name, and the simulation that should form the basis for the animation as well as the corresponding result group definition is selected.

When the "Animate" button is clicked, the animation is created. Each item in the results group receives a legend, which shows in the Display tab of the ArcGIS table of contents. You can step through time steps in the ani-mation toolbar that has standard player buttons (start, stop, pause, back, forward, first, last). Notice that the maximum number of time steps for any animation is 250. If there is more than this number of time steps in you simulation, you will be prompted to select the time step range for the ani-mation.

The animation toolbar is shown below.

When the "Create .avi file" button is clicked, an animation in the .avi file format is created.

142 MIKE BASIN

14 MACRO PROGRAMMINGMIKE BASIN's computational core ("engine") can be accessed program-matically, giving you the flexibility to automate or change computations in almost any way you want.

Many users program Visual Basic macros, mostly from Microsoft Excel or from ArcGIS. You can also use any other program/programming language that supports the Microsoft COM technology (Visual C++, Delphi, etc), or any .Net language (C#, Visual Basic .Net, etc).

Running MIKE BASIN in this way is like pressing the 'run' button in the user interface, but circumventing the ArcGIS user interface. Input to the model is instead specified directly in the macro/program. The approach is useful when running many MIKE BASIN simulations. Furthermore, it gives access to functionality not available in the user interface, because simulations can also be run one time step or even one iteration at a time. For example, you can

Do rapid sensitivity analysis through (many) Monte-Carlo simulations;

Rapidly execute and analyse multiple scenarios;

Post-process results using Excel's statistics functions, ArcGIS charting, or other third party program;

Implement any mechanism besides MIKE BASIN's standard allocation algorithms (e.g., site-specific reservoir operation rules);

Dynamically control the simulation (step-wise simulation, hotstart from any previous time step, or even iteration within a time step):

Easily create simple ArcGIS or Excel user interfaces to site-specific MIKE BASIN models (that can be executed also by non-GIS users); or

Do optimization of any kind through Excel's Solver tool ('Data' menu).

Prior to using MIKE BASIN from a macro or another program, you have to set up your model in the standard ArcGIS user interface. You should also run at least one simulation to make sure all your inputs are valid. Fix-ing invalid inputs is much easier in the user interface than from a macro.

Through the COM/.Net interface, you can access and manipulate any input and output otherwise contained in time series to or from your model, and you can change any input parameters and look-up tables otherwise specified directly in dialogs. You cannot change the model structure (e.g., add or delete nodes, re-define priorities, etc). Simulations from a macro or

143

Macro programming

other program are much faster when file output is disabled (the default set-ting).

14.1 Overview of interfaces and enumerations

There are two interfaces, or objects, that the MIKE BASIN engine pro-vides, namely

1 DHI_MikeBasin_Engine.Engine

2 DHI_MikeBasin_Engine.ModelObject.

The Engine is the core object that contains the entire model setup and sim-ulation information. The model setup itself is composed of ModelObjects.

ModelObjects can be physical features or network elements, such as nodes, reaches, and catchments. Additional types of ModelObjects are logical or computational entities, such as allocation rules and water quality models.

Note the difference in architecture to what you may be used to from work-ing just with the ArcGIS user interface. In ArcGIS, you have features, and each feature (or network element) has a property dialog. In these dialogs, also rules and water quality parameter sets (models) applicable for the fea-ture can be defined. Under the hood, however, rules and water quality models are separate entities. Relationships define the link between fea-tures and logical entities. The ModelObject interface also provides meth-ods to return the rules applicable for a feature-type ModelObject.

Both MIKE BASIN interfaces contain methods that refer to some enumer-ations that are defined in the DHI Mike Basin Data Access Component (DHI.MikeBasin.Data.tlb).

14.2 Macro Assistant

The easiest way to get started with programming MIKE BASIN is to use the Macro Assistant from the MIKE BASIN menu in ArcGIS. It generates skeleton code that you can execute right away, or expand with your own logic. All commonly used methods and functions are contained in the auto-generated code, along with comments. A full documentation of all methods is given in For Visual Basic macro programming (p. 241) . The syntax is that for Visual Basic, (C# for .Net-only methods), but other lan-guages' syntax is similar.

144 MIKE BASIN

Macro Assistant

When a model has been set up and made a successful run in the normal way using the run button, the Macro Assistant can be accessed from the MIKE BASIN pull down menu, see Section 2.1.2. A dialog will appear, which includes all the model the building blocks and the structural link-ages of the model set up, see Figure 14.1. You can then specify the varia-bles required for inputs to be set and the results to be retrieved in the macro.

Figure 14.1 Macro Assistant for transferring the need variables to the Macro script

This is useful if you wish to run MIKRE BASIN from a macro where you need rules, which is not a standard in-built MIKE BASIN rule, e.g. if a certain condition should be applied (input to be specify) based on a certain condition existing at a certain time step (retrieve a result) . An example of this could be: If a water user node downstream a reservoir with a hydro-power station experience a water deficit, release water through the hydro-power equivalent to the water deficit.

When you have specified all the variables required for your rule, you can generate the macro. An example of a macro script is given in Figure 14.2. Notice that the generated macro automatically includes all the necessary conditions for running compiling and running the macro. It furthermore includes the correct references to the working directory, simulation result (it is using the simulation ID adding “with MACRO name”) etc. It also includes the required variables.

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Macro programming

14.3 Adding references

Prior to program with MIKE BASIN, you have to add a reference to it. From ArcGIS or Excel, choose the Tools menu, then select Macro and then Visual Basic Editor. In the Visual Basic Editor that comes up, choose the Tools menu, then select References. In the dialog that appears, scroll through the list available references and check

DHI Mike Basin COM / .Net engine interface (DHI.MikeBa-sin.Engine.tlb/.dll)

DHI Mike Basin Data Access Component (DHI.MikeBa-sin.Data.tlb/.dll)

Note that when you use Visual Basic macros from ArcGIS, your list of ref-erences will contain many ESRI components. None of these are required for MIKE BASIN. So you can simply copy-and-paste a Visual Basic macro from ArcGIS to Excel and run it from there, as long as you define the above two references. In other words, running MIKE BASIN outside its ArcGIS user interface does not require an ESRI license.

14.4 Editing the Macro

The generated code can be viewed by selecting Tools -> Macros ->Visual Basic Editor in the ArcGIS toolbar. The code is located under "Modules", "MIKE BASIN Modules". The name of the macro is the one that was specified in the Macro Assistant dialog.

The Macro can then be edited with the appropriate logical statements and mathematical expressions, compiled and executed, and the default varia-bles can be renamed. The access

If you wish to run the Macro from another application, e.g. EXCEL, the code needs to be copied to the Excel Visual Basic Editor (From Excel, click Tools -> Macros ->Visual Basic Editor and copy/paste the code ).

After running the Macro, the results can be viewed in MIKE BASIN’s result presentation section in the same way as other runs executed from the Run MIKE BASIN Simulation button.

146 MIKE BASIN

Editing the Macro

.

Figure 14.2 Example of a script generated with the Macro Assisstant.

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Macro programming

148 MIKE BASIN

Theoretical background (brief)

15 OPTIMIZATIONOptimizing an existing water resources management strategy can be a low cost investment with considerable benefits. It may even be essential, for example, when the construction of new reservoirs is not feasible. How-ever, the objective of the optimization and the possible measures to achieve the objective depend on the application. Site-specific constraints often further complicate the problem.

Optimization in MIKE BASIN is flexible and general. Any model result can be included in the objective. Unlike some other water resources mod-els, MIKE BASIN's optimization capabilities are not limited to a linear program solver for finding the cheapest route in a network flow model. Instead, MIKE BASIN uses a built-in nonlinear program optimization algorithm that can handle the inherently non-linear responses of, for example, reactive water quality models or reservoir tailwater elevation.

The optimization user interface lets you formulate any combination of minimum, maximum, and goal attainment objectives. Futhermore, if you need to further customize your objective function, or if you prefer another optimization algorithm (e.g. Excel, Matlab, GAMS, etc), you can use MIKE BASIN's COM interface to call the MIKE BASIN simulation engine. See more on this topic in Chapter 20 For Visual Basic macro pro-gramming (p. 241)

15.1 Theoretical background (brief)

The general principle of optimization is, in a sense, the reverse of a simu-lation. In a simulation, known inputs are transformed into results. In an optimization, some desired results are known, but the inputs to achieve them have to be found. In a simulation, usually many results are of interest (e.g., the flow pattern in all rivers). In an optimization, usually only few key results have desired values. To achieve such desired results, only a few inputs are generally freely adjustable. For example, when trying to optimize hydropower production, it is often not an option to raise the flood control level of the supplying reservoir.

For those not familiar with optimization, here is a brief introduction to the concept. A more detailed theoretical background for the numerical optimi-zation solver is described in Spellucci (1998).

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Optimization

Mathematically, a simulation model m can be viewed as one ("big") func-tion with many inputs x and many outputs y

y=m(x) (15.1)

According to the train of thought in the preceding paragraph, the optimiza-tion problem would be solved if it were possible to invert the "model" function

x=m-1(y) (15.2)

Unfortunately, such an inverse model can essentially never be formulated analytically. Therefore, optimization uses iterative simulations with "trial values" for x until

(15.3)

Note the approximate equality here, as the iterative solution generally only converges towards, but often far from, the desired value. In a common type of optimization problem, minimization/maximization, a desired value does not even exist. Rather, the aim is to find the minimum/maximum attainable value of y.

(15.4)

Technically, maximization of m is the same as minimization of -m. Also the problem of attaining a desired value of all elements of y can be formu-lated as a minimization, namely

(15.5)

where the double bars indicate some kind of norm, most commonly the sum of squares. The expression to be minimized is generally called "objective function" (OF).

So while there may be many terms y desired, the objective function itself returns a single value. Weights on the individual terms can be used to indi-cate their relative importance, generally a subjective choice. Pareto opti-mization is an approach to solve multi-objective optimization problems, yielding a family of suggested solutions rather than a single one. There is still an element of subjectivity in choosing among those solutions, and the

ydesired m xoptimal( )≈

ydesired min m xoptimal( )≡

min ydesired m xoptimal( )–

150 MIKE BASIN

Theoretical background (brief)

method is computationally very expensive. Pareto optimization is planned for the next version of MIKE BASIN.

The numerical challenge in optimization is to find an algorithm that deter-mines how trial values are adapted from iteration to iteration. The algo-rithm should find the optimum with as few iterations, i.e., trial simulations, as possible. Many algorithms, including the one implemented in MIKE BASIN, are based on finding the gradient of the objective func-tion (or rather its finite difference approximation). With the gradient known, subsequent iterations can "go downhill" the objective function. Because most objective functions are functions of many variables, "down-hill" is in as many dimensions. Thus generally, having gone downhill some distance, a "saddle" is encountered, so a new gradient/downhill direction is to be found - and so on.

Numerical optimization is generally a computationally intensive task. With the objective function being of dimension equal to the number of variables (n) to be optimized, each gradient calculation required 2n simu-lations (for a centered finite difference). Thus if at all possible, try to keep n small. This piece of advice is generally valid also with some other diffi-culties encountered with practical optimization, as described in the follow-ing.

15.1.1 Lack of sensitivityThe gradient of the objective function can be viewed as the sensitivity of the model to changes in its inputs. In order for the optimization algorithm to find a downhill direction, there has to be a non-zero sensitivity at the starting point. Be aware of this when your optimization seemingly does not go anywhere. For example, say your objective is to minimize a relative deficit of a water user by changing its reduction level at the supplying res-ervoir. Now if the user's priority is so low that there will always be 100% deficit, the optimization will quit soon. A more subtle reason for the opti-mization to terminate prematurely would be a lack of sensitivity just at the starting guess of the optimization, e.g., if the initial guess for reduction level is lower than the lowest water level ever attained in a simulation. Starting from another (higher) initial guess, the optimization would find an optimum easily.

15.1.2 Local vs global optimaYou should also be aware of the risk of finding only a local rather than a global optimum. The algorithm may find a nice downhill path to the bot-tom of some valley - but there is another valley just next to it that is much lower still. The intermediate ridge, however, keeps a gradient-based algo-rithm from ever discovering it. There are other types of algorithms non-gradient-based that "look at" many distinct points on the objective func-

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tion surface. Even those, however, often fail to find a global optimum because with many variables to be optimized, even those algorithms can "look everywhere". Furthermore, such algorithms are much slower than the one implemented in MIKE BASIN. If you suspect that an optimum you found is just a local one, it is a good idea to optimize again, but from a different starting guess, and see if you can reach a smaller objective func-tion value.

15.1.3 Ill-defined problems At an (or hopefully, the) optimum, the surface of the objective function is flat. Changing parameters from their optimum value no longer decreases the objective function value. In this sense, the optimization has succeeded, but be aware of situations the objective function has a large flat "plain" rather than a well-defined lowermost point. A "flat plain" means that even for variable combinations far from each other, the objective function is almost the same. No one combination can be called the optimal one, there is little sensitivity at the optimum. This situation is called an ill-defined problem, and is caused by strongly correlated variables. For example, the effect of raising a reservoir reduction level can be outweighed by simulta-neously decreasing the corresponding reduction factor. These two varia-bles should thus not be optimized simultaneously. In other situations, an ill-defined problem may not be an evil - it just shows that many seemingly very different strategies to solving a problem are almost equally good. However, many people find this counter-intuitive, and hence it may be dif-ficult to communicate such a result.

15.1.4 SummaryAs seen from the above, optimization should not be used as a black-box approach. It is recommended that you first run several simulations with inputs changed manually, in order to get a feeling for the system's sensitiv-ity to changes, likely approximate optima, and counter-acting variables. The "art" in optimization is often not the numerical solution algorithm, but to formulation of a solvable problem.

15.2 Working with Optimization

Three dialogs in MIKE BASIN relate to optimization:

The Optimization Problem dialog lets you define the variables (model inputs) to be optimized and the objective to be optimized for (model results). This dialog also shows the results, i.e., the optimal values of the variables. This dialog is what you will work with mostly.

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Working with Optimization

The Run MIKE BASIN dialog lets you choose between running a sim-ulation and an optimization, and in the latter case, how to treat errors in iterations of the optimization

The Options dialog lets you set some numerical parameters for the optimization algorithm. In general, however, the default values will be fine.

15.2.1 Optimization Problem DialogAn optimization problem in MIKE BASIN is defined from the "Optimiza-tion problem…" item in the MIKE BASIN Menu (Figure 2.2 ). The dialog that comes up looks almost the same as the Macro Assistant Dialog, because the underlying concept is very similar. You choose a few of the many inputs to a MIKE BASIN model (the ones to be changed) and a few of the many outputs (the ones that are to be compared to the goal). The following sections describe the items in the optimization dialog that are different than the Macro Assistant Dialog.

Variables to be Optimized tabThe inputs, as defined in the Theoretical background (brief) (p. 149), to be optimized can be any period with any time series and any parameter. Rows in lookup tables, although inputs as well, cannot yet be optimized in the current version of MIKE BASIN. Each row in the "Variables to be opti-mized" tab of the Optimization Problem dialog corresponds to one ele-ment xi in the vector x.

Note that if a variable refers to a period within a time series, only values in existing time steps can be changed. If the period start and end do not match perfectly any existing time step in the input time series, the closest ones will be used instead. Thus be aware that if you would like to, say, optimize some input for a few days only, you cannot use a monthly time series in the regular simulation input. Also note that there is no recycling. In other words, while it is generally fine in MIKE BASIN to specify an input time series for any year (as long as it covers a whole year), in the optimization must specify the actual year in the time series.

Each of the inputs to be optimized can be constrained to remain within bounds. Defining bounds increases the chance of the optimization con-verging to a physically meaningful optimum. Unbounded optimization problems may give solutions where variables approach +/- infinity, or where the mathematically best solution is not realistic (e.g., negative con-centrations) or feasible (e.g., a flood control level cannot exceed a dam crest level). Furthermore, the optimization algorithm used in MIKE BASIN examines the simulation results at the bounds of the variables' ranges (as the best solution is often found there). So it is advised that you

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Optimization

define your bounds always, and as narrow as possible. Accordingly, the user interface sets some default bounds for every variable that you choose for the optimization.

Apart from upper and lower bounds, the Optimization dialog also lets you define a first guess for every variable. If you leave this field blank, the optimization will by default start from the value that the corresponding variable has in the underlying simulation. You should use this field in situ-ations where you detect a lack of sensitivity at the default first guess, or to make sure (or at least likely) that your optimum is a global one.

Objective Function Terms tabThe objective function, f, can be defined to take into account any MIKE BASIN simulation output. Each row in the "Objective function terms" tab of the Optimization Problem dialog corresponds to one term in the objec-tive function. All terms are added to yield the total (scalar) objective func-tion value. To enable goal attainment as well as proper minimization within the same formulation, the objective function f is computed as

(15.6)

where yj is one of m MIKE BASIN simulation results, gj is a goal value for that result, pj is a power, and vj is a weight. The weight can be differenti-ated as a weight below a goal value and a weight beyond a goal value:

(15.7)

A simulation result is generally the average value of any simulation output over a user-defined period. The average can also reduce to a time step's value if the averaging period is set to the time step.

The above formulation of the objective function accommodates for the basic types of objectives for each term in the summation in (15.6). The

f x( ) vj yj gj–( )pj

j 1=

m

∑=

vj

vj – : yj gj≤

vj – : yj gj>

=

154 MIKE BASIN


following table shows how to set the goal, power, and weights parameters for each type.

Note that setting a weight to zero can lead to an optimization that seem-ingly does not finish successfully. For example, take a single-term objec-tive function. Now if yj is greater than yg, and vj+ is set to 0, then there is no sensitivity in the objective function to (small) changes in x. This is no problem if your first guess for x causes the term to be on that side of where v > 0. The optimization will find the desired value. When starting on the other side, however, the optimization will terminate quickly without suc-cess. Therefore, it can be advisable to use a small non-zero value rather than zero, even though the latter is theoretically appropriate.

The relative magnitude of the weights determines the importance of every term in the overall objective function. Also choosing a high power p can make the corresponding term dominate the objective function, at least when y is far from yg. Be careful with setting weights very large or small, as numerical precision in gradient calculation diminishes as the objective function evaluates to orders of magnitude far from 1. A rule of thumb may be to try to keep it between 1E-4 and 1E+4.

Table 15.1

for a model result yj, to ..., set:

gj pj vj- vj+

Minimize it 0 1 >0 = vj

Maximize it 0 1 <0 = vj

Make it attain a goal yg

yg 2, 4, etc. >0 = vj

Make it exceed a goal yg

yg 2, 4, etc. >0 0

Make it remain below a goal yg

yg 2, 4, etc. 0 >0

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Optimization

15.2.2 Run MIKE BASIN dialog - OptimizationAt the top of the Run MIKE BASIN (p. 28) dialog,

you can choose between running a simulation and an optimization. If you choose Optimization, the problem defined in the Optimization Problem dialog is solved.

If you choose Optimization, a combo-box appears, where you choose one of the three options for how to handle errors in the internal simulations called by the optimization algorithm. Since inputs for these simulations are generated partially by the optimization algorithm, you no longer have full control over their validity. For example, when searching "downhill" the objective function, the optimization algorithm may perturb some input to an invalid value. Often, the algorithm can recover from such errors and revert to an earlier iteration's solution. The algorithm is not so robust to failure in calculating gradients. This is another reason why you should set bounds for the variables to be optimized. In detail, the options are

Ignore: No dialogs are shown, the optimization keeps going (but often ends with a failure). This option is mainly intended for automated use, e.g., if you build an online application on top of MIKE BASIN.

Report: Show dialogs with error reports, helping you diagnose prob-lems. You can choose to let the optimization continue. The default option.

156 MIKE BASIN


Stop: The first error causes a dialog with an error report to show, then the optimization stops. Use this option if you only want to allow per-fect optimization runs.

Click the Run button to start the optimization. The progress bar will, besides the usual information, also show the iteration number and the objective function value. In this way, you can follow improvement. If you hit Cancel on the progress bar during an optimization, you will be prompted whether you want to keep the best results so far. Thus, if you feel improvement becomes insignificant (the objective function value stagnates), you can simple Cancel to save time.

When the optimization finishes, a status dialog is shown. It summarizes the result and lets you view the log file with all its details on all iterations and the final solution. If the result is not perfect, the status dialog will - if possible - show suggestions on how to change the optimization numerical parameters. The optimal variables are shown as a simple vector, in the same order as they are defined. You may also want to go back into the Optimization Problem dialog to see the full definition of each variable along with its optimum.

When the optimization finishes, a final simulation is run with the optimal variables found, and added to the list of simulations. Thus you can also see all MIKE BASIN results for the optimum.

15.2.3 Options Dialog (Advanced tab) - Numerical SettingsIn the Options (p. 25) dialog, you can specify some numerical parameters for the optimization algorithm.

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Optimization

Finite difference factor for numerical gradient: The gradient of the objective function is found by a centered finite-difference approximation, for which each variable xi is perturbed relative to its magnitude. Given a finite difference factor h, the perturbation is by +/- hxi (by +/- h if x = 0). For h, a range of 1E-2 to 1E-8 is recommended. Use a large value if you experience little sensitivity at your starting guess, a small value for more accurate results. Very small values can result in numerical noise.

Convergence criteria for objective function: When either one of the cri-teria that can be defined in the dialog is fulfilled, the optimization algo-rithm finishes.

Flatness: At a minimum, is objective function surface is flat, in theory perfectly. Flatness is measured as the norm of the gradient vector multi-plied by its transpose (the Hessian matrix). Given numerical imprecision, this norm will never be perfectly zero, so some tolerance can be set. High values will lead to earlier, but maybe premature, termination.

Absolute value: The user can also choose to accept an optimized result if the absolute value for the objective function drops below this threshold. Such a result will not be a perfect optimum, but it could be "good enough".

Stagnation: To avoid long optimization runs without noticeable improve-ments, MIKE BASIN optimization can also stop when the flatness does not improve by more than this value over 5n iterations, n being the number of variables optimized.

Tau: A numerical tolerance for deviations from bounds internally used in the algorithm. If nothing else works, try changing this parameter within 0.01 and 1.

15.3 References

/1/ Spellucci, P. (1998), An SQP method for general nonlinear pro-grams using only equality constrained subproblems, Math. Prog. (82), p. 413 - 448.

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Modeled Substances

16 WATER QUALITY MODELINGMIKE BASIN can simulate water quality in surface and groundwater, with solute inputs from non-point and/or point sources. The WQ module is not included in MIKE BASIN's basic version, but must be purchased seperately. If you have a license for the water quality modules, you will be able to choose the WQ module from the The Water User Property dialog. (p. 23) dialog, either when you start a new project or when you want to extend an existing water-quantity project with WQ processes.

MIKE BASIN WQ can simulate reactive steady-state transport of the most important substances affecting water quality. The degradation proc-ess for all substances is described including reactive transformations (e.g., ammonia / nitrate, DO / BOD). In general, first-order rate laws are assumed. The water quality simulation can, in an approximate way as MIKE BASIN is not a hydrodynamic model, include dissolved oxygen (DO). Re-aeration from weirs is accounted for.

The steady-state approach is consistent with MIKE BASIN's solution to the water allocation problem. Thus, advection can not be modeled prop-erly with MIKE BASIN. In other words, pulses of solute entering the stream do not travel downstream as simulation time advances.

In reaches where you specify routing (linear, Muskingum, wave transla-tion), the water quality simulation can (if you so choose) properly reflect the residence time and the effects of mixing between reach storage and inflows. The same holds (always) for reservoirs and groundwater, the two other storages of water in MIKE BASIN.

16.1 Modeled Substances

BOD5:Total organic matter expressed as biological oxygen demand (mg O2/l).

The biodegradable part of the organic matter gives rise to oxygen con-sumption. The biological oxygen demand is measured by registering the oxygen consumed during the degradation for a period of 5 days. BODd included in the equations below corresponds to the equilibrium (large-time) BOD value. The BOD5 values are converted to BODd values using the following equation (given the degradation rate coefficient kd3):

(16.1)BOD5 BODd 1 kd35 days[ ]–( )exp–( )=

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Water Quality Modeling

If you want to model BOD as conservative, set kd3 = 0, and the above conversion is skipped.

NH3: Ammonia concentration (mg NH3-N/l)

NO3: Nitrate concentration (mg NO3-N /l)

DO: Dissolved oxygen concentration (mg O2/l)

Ptot: Total Phosphorus, including phosphate on particulate matter in the water (mg/l)

E.coli:E. coli count (bacteria/100ml)

User: a 'wild-card' user-defined substance, either conservative or undergo-ing first-order decay. This 'wild-card' substance gives greater flexi-bility for modeling case-specific water quality issues, e.g., salinity (mg/l).

16.2 Processes: Equations

The following equations are used in MIKE BASIN:

Oxygen consumption from degradation of organic matter:

(16.2)

Ammonium processes:

(16.3)

Nitrate processes:

(16.4)

Oxygen balance:

(16.5)

dBODd

dt------------------ kd3BODd=

dNH3

dt-------------- Ydkd3BODd k4NH3–=

dNO3

dt-------------- k4NH3 k6NO3–=

dDOdt

------------ k2 cs DO–( ) kd3BODd– y1k4NH3– R B P–+( ) d⁄–=

160 MIKE BASIN

Processes: Equations

Total phosphorus, E.coli count, and the 'wild-card' user-defined substance are presumed to follow a first-order rate law (exponential decay). With 'X' representing any of these substances, the equation is

(16.6)

In the above equations, the parameters are explained below. Except for those that are hard-coded, all parameters can be set by the user in the 'WQ options' menu (WQ parameters).

kd3: Degradation rate coefficient for BOD at 20°C (1/day)k2: Re-aeration rate coefficient at 20°C (l/day) (computed

internally)k4: Nitrification rate coefficient at 20°C (1/day)k6: Denitrification rate coefficient at 20°C (1/day)kcod: Degradation rate coefficient for COD at 20°C (1/day)kecoli: Degradation rate coefficient for E. coli at 20°C (1/day)kPtot: Degradation rate coefficient for total phosphorus at 20°C (1/day)kuser: Degradation rate coefficient for the user-defined substance at

20°C (1/day)Cs: Saturated oxygen concentration (mg O2/l)

(For water at 20°C: Cs = 9.02 mg/l.)R: Oxygen consumption from respiration (g O2/m2/day)P: Oxygen production from photosynthesis (g O2/m2/day)B: Sediment oxygen demand (g O2/m2/day)d : water depth (m)Yd: Nitrogen content in organic matter (mg NH3-N/mg BOD).y1: Yield factor: Relative amount of oxygen produced during

nitrification (gO2/gNH3-N)

All rate coefficients (k…) are temperature-dependent.

In many cases Total Phosphorus can be regarded as conservative. If that assumption is valid, simply specify the degradation constants as zero.

The rate k2 is calculated with the empiral O’Connors-Dobbins formula:

(16.7)

where v is flow velocity in m/s and d is depth in meters and k2 is in 1/days.

dXdt------- kXX–=

k2 3,9 v1 2⁄ d 3 2⁄–⋅ ⋅=

161


The coupled first-order equations are solved numerically with a 5th order Runge-Kutta scheme. The integration is from zero to residence time, either in the reach or in the reservoir. Reservoir time calculations are described as part of the help for the river and reservoir WQ property dia-logs, respectively. Note that the numerical solution can become inaccurate if the flow in a reach is very small. A warning will be issued if that is the case.

As a steady-state model, MIKE BASIN can only simulate DO approxi-mately. Accordingly, you can choose to not include DO in the water qual-ity simulations on the Options dialog. If you do so, equation (16.5) is not included in the solution. You can also skip the next section on re-aeration from weirs if you do not model DO. Finally, the data requirements for res-idence time calculations in reaches become less, because flow velocity is no longer a required quantity

16.3 Rates: Temperature Dependency

Reaction (degradation) rates are generally dependent on temperature. The formula used to express this dependency in MIKE BASIN is

(16.8)

where R(T) is a rate coefficient for temperature T, R20 is the rate coeffi-cient at 20 degrees Celsius, and RateCorr is specified in the Water Quality Settings dialog. The default value for RateCorr is 1.07, such that a rate coefficient at, e.g., 30 degrees Celsius is twice the rate coefficient at 20 degrees Celsius (1.0710 = 2.0).

The temperature correction applies to all rate coefficients in the equations describing water quality.

16.4 Sources

Sources of pollution are generally divided into point and non-point. This distinction may not always be clear-cut in reality. Particularly MIKE BASIN's non-point modeling features are very flexible, and may in many cases suffice to also model 'scattered point sources'. Non-point sources must be specified as properties of the catchment. The Load Calculator is a convenient pre-processing tool that generates boundary conditions for the entire model, taking advantage of existing related GIS data (land use, pop-ulation, etc).

R T( ) R20 RateCorr T 20C–( )⋅=

162 MIKE BASIN

Within-Catchment Decay for Non-Point Sources

Proper point sources are modeled as water user nodes, with boundary con-ditions (effluent concentration or mass flux) specified there. These bound-ary values are effective only in the return flow from the water user. Simulation results at water user nodes will show the concentrations found in the incoming extracted water. You should not worry not to find the specified boundary concentrations in the simulation results.

16.5 Within-Catchment Decay for Non-Point Sources

Because MIKE BASIN is a network model, inflow and extraction of water occurs only at nodes. Therefore, input of solutes also occurs at nodes, either catchment nodes (non-point sources) or water user nodes (point sources). Decay is then modeled to occur within reaches downstream of the entry node. While this approach is appropriate for point sources, applied strictly, it would mean unrealistically large jumps in concentra-tions at catchment outlets. In reality, runoff and this solute enters the river reach inside catchment over the entire length of the reach.

To reconcile the network modeling concept with diffuse solute entry along reaches, it is possible in MIKE BASIN to specify a "reach residence time fraction" in the water quality parameter set dialog. If the residence time in the reach within a catchment is T, then non-point solute from the catch-ment is decayed for a residence time of fT, where f is the residence time fraction. Under the assumption of spatially homogeneous solute entry along the length of the reach, a good default value for f is 0.5.

If the catchment contains more than one reach, the total residence time in all reaches is used for computing decay, while f is taken as the value for the lowermost reach inside the catchment.

Note that even with a non-zero reach residence time fraction, the non-point solute is not actually mixed with that in the reach before the catch-ment node, which is also where all runoff still enters the river. The equa-tions for decay are solved separately for the reach and the diffuse solute, not for any average concentration. The rationale for separating the two is that decay for diffuse solute often occurs in small streams within the catchment, but not resolved in the MIKE BASIN model. If you wish to model water quality in detail, you should work with small catchments

163


such that non-point pollution inputs do not accumulate significantly before entering a stream.

Within the catchment, non-point solute inputs are decayed for a residence time fraction f of the total residence time T. Regular decay occurs for all solutes within reaches downstream of the catchment, as determined by the residence times in those reaches.

16.6 Reservoirs: Water Quality

Water quality processes are modeled in reservoirs under the assumption of a well-mixed reservoir. The process equations are the same as in rivers. Like in rivers, degradation is modeled as an initial value problem. In other words, degradation of solute entering the reservoir from upstream is mod-eled by integrating the coupled differential over the time step length.

Initial conditions at the start of the MIKE BASIN simulation can be speci-fied either as pristine (zero concentrations except for DO, which is at satu-ration) or as steady-state after time step 1. The reason for 'waiting' until after time step 1 is that inflow fluxes into the reservoir are result of the computations during time step 1 (groundwater 'reservoirs' are different, because for those, inflow fluxes are user-specified input).

The single difference in water quality process equations between rivers and reservoirs concerns phosphate (P_tot) sedimentation in reservoirs. The latter is modeled in MIKE BASIN by a modified Vollenweider equa-tion

(16.9)

where Pstart and Pend are phosphate concentration at the start and end of the time step, respectively, a is the Vollenweider coefficient (dimension-less), t is the time step length, V is reservoir volume at the end of the time

Pend a Pstart⋅ 1 sqrt tV Q⁄( )

---------------- +

⁄=

164 MIKE BASIN

Groundwater: Water Quality

step, and Q is reservoir release during the time step (V/Q indicates resi-dence time in the reservoir). The Vollenweider coefficient is generally found by calibration, although in the original Vollenweider model, it is 1.0.

It should be pointed out that the above formulation is unit-consistent as opposed to some other 'Vollenweider' equations in the literature. Note also that Vollenweider's equation was originally developed for a steady-state situation (with annual average values for V and Q), whereas MIKE BASIN (as other models) assumes it to be valid also in the general case, i.e., when V may differ from start to end of a time step. However, any changes will generally be very small relative to the magnitude of V, and thus have little importance for the above equation.

16.7 Groundwater: Water Quality

Solute transport in groundwater is accounted for, assuming a perfect mix-ing model within the linear reservoir concept (see the figure there for an explanation of the variable names). The coupled differential equations solved are (written here for a particular species):

(16.10)

(16.11)

(16.12)

(16.13)

The approximation in the third line is to use an average value, computed as the arithmetic average of the expression in square brackets for the beginning and the end of a time step, respectively.

∂ c1 h1 L1–( )( )∂t

-----------------------------------

k1– ki–( ) h1 L1–( )c1 qrecharge qstream_seepage+( )crecharge,stream_seepage+=

∂ c2h2( )∂t

------------------ ki h1 L1–( )c1 k2 h2 L2–( )c2 qpumpingc2

ki h1 L1–( )( )c1k2 h2 L2–( ) qpumping+

h2--------------------------------------------------- c2h2–≈

––=

∂c1

∂t-------- r1c1–=

∂c2

∂t-------- r2c2–=

165


Transport in groundwater is modeled as conservative or first-order decay (given the rate constants r in the above equation). User input can be speci-fied in the water quality tab of the specific runoff dialog.

The required input includes a time series of solute fluxes from catchments to groundwater (mass/area/time). Generally, the user will have to provide this time series. Only the Daisy GIS extension will automatically generate the appropriate time series as a result of the Daisy model run.

Initial conditions in the groundwater can be either pristine (zero concen-trations for all solutes) or steady-state. Under the latter option, the concen-trations c are computed as

(16.14)

where M is solute flux, taken from the input time series at the simulation start time [kg/s/m2 in SI] and R is specific groundwater recharge [m3/s/m2 = m/s in SI].

Polluted stream seepage reduces loads (solute mass) in surface water by its relative magnitude (stream seepage / total flow). In other words, the simulation is conservative with respect to concentrations at catchment nodes. Recall that stream seepage is a fraction of the flow in the branch upstream of a catchment node, and not a fraction of the flow at the catch-ment node (which is larger due to surface runoff from the catchment).

16.8 Re-aeration from Weirs

An expression suggested by Holler is selected to describe the ‘ taking place when river water overflows weirs

(16.15)

where DOd is the dissolved oxygen concentration downstream to the weir, Cs is dissolved oxygen saturation, and DOu is the dissolved oxygen con-centration upstream to the weir. The parameters are:

a weir coefficient. This coefficient (dimension: 1/Length) is generally dependent on the weir type. As a default, Holler suggests a = 0.21/m. This value may be adjusted based on actual measurements.

c M R⁄=

DOd CsCs DOu–

1 ah+-----------------------–=

166 MIKE BASIN

Re-aeration from Weirs

h weir height. Strictly speaking, this is the water level difference over the weir. For MIKE BASIN, h is viewed as the sum of heights of all weirs on a reach. Accordingly, you should break a long branch into smaller segments (by inserting simple nodes) if more accurate modeling of re-aeration is desired.

Both parameters are specified for each river reach.

167


168 MIKE BASIN

Sources

6 LOAD CALCULATORThe Load Calculator is used to determine pollution loads in river basins. It can be applied as a stand-alone tool for calculating average mass fluxes of pollutants for individual sub-catchments (e.g. kg/catchment/year) or on a raster grid basis (e.g. kg/grid/year). Alternatively, it can be used to provide the pollution loading for a MIKE BASIN Water Quality model or for a MIKE 11 solute transport (AD) model.

Pollution loads may include both point and non-point sources. All loads are initially calculated as constant mass fluxes for each sub-catchment, e.g. kg/year, however when applying the Load Calculator together with e.g. the MIKE BASIN WQ model there are several ways to translate the constant mass fluxes into mass flux time series depending on e.g. runoff time series or any other known temporal variations.

Distance specific decay or retention of pollutants can be included taking into account the distance between the location of the pollution sources and the presumed outlet in the river network.

The Load Calculator is accessed from the MIKE BASIN/MIKE 11 GIS pulldown menu under the menu item Load Calculator…

The main Load Calculator dialogue consists of three parts:

Sources - for specifying pollution sources,

Transport - for specifying the transport and retention of pollutants, and

Output - for specifying how the output is to be stored

6.1 Sources

In the Sources section of the dialogue all pollution sources are defined and specified individually. An unlimited number of sources can be specified.

Each source has a unique set of required input data, but the data input is very similar in all four cases. As illustrated below,

55

Load Calculator

.

each sources tab can be divided into

a Shape file attributes section

a Time distribution (alpha time series) section, and

a source specific section that in three of the four methods includes a Runoff Coefficients button.

Below these sections are a series of buttons, where new sources are added by clicking on the Add... button, existing source tabs are removed via the Remove button, and a summary table can be viewed using the View Table button. The summary table of all specified sources is described in Section 6.1.7 Load Sources Table (p. 63).

When adding new sources, there are four different methods available to specify the source, which are described in the following sections:

Fertilizer Sources (p. 58),

Livestock Sources (p. 58)

Domestic Sources (p. 59), and

Point Sources (p. 60).

6.1.1 Shape file attributesThe left hand side of the Sources tab includes the three attributes in the shape file used to define the source. The first one is a Layer name, fol-lowed by an ID/Name field, and lastly by an Amount/Count field.

Layer nameSelect a polygon shape file from the scroll down menu representing any administrative or statistical unit, which includes data on fertilizer applica-

56 MIKE BASIN

Sources

tion, population numbers, etc. The shape file must be added to the TOC to be selectable from the scroll down menu.

ID/Name fieldSelect a field in the attribute table of the layer that includes a unique ID or Name of the administrative or statistical unit.

Count/amount fieldSelect a field in the attribute table of the layer that includes data of the fer-tilizer application, head count, release amount, etc.

6.1.2 Time distribution (alpha time series)

If either the MIKE BASIN output or MIKE 11 output check boxes are checked in the Output section of the Load dialogue, a dimensionless time series must be specified. The time series is applied as a temporal multipli-cation factor to distribute the mass fluxes of the pollution source in time. This time series is input in the upper right hand side of the Sources tab.

Warning! If you set any alpha values different than 1.0 for agricultural sources (see Fertilizer Sources (p. 58) or Livestock Sources (p. 58)), you will likely get mass balance errors. It is recommended that you only use alpha values equal to 1.0 for agricultural sources.

If a Distributed solute source time distribution time series is already registered in the Geodatabase, the time series can be easily accessed and selected through the drop down menu. Alternatively, you can use the New icon to create a new timeseries with a default value of 1, or you can use the Open icon to open an existing time series.

The two additional icons are

, which plots/edits an opened time series, and

, which displays the properties of an opened time series

6.1.3 Runoff Coefficients buttonFor three of the source types, the runoff coefficients must be specified as a dimensionless number. The number can vary in space by assigning differ-

57

Load Calculator

ent runoff coefficients to different polygons (e.g. administrative or statisti-cal unit). For details on how to interpret and apply runoff coefficient, see the Runoff Coefficients Editor (p. 61).

6.1.4 Source Editors

Fertilizer Sources The Fertilizer source type typically represents artificial fertilizers, such as nitrogen and/or phosphorous. Other pollutant components may also be included as a fertilizer source.

A fertilizer sources must be specified individually for each type of pollut-ant. For example, to simulate both nitrogen and phosphorus two fertilizer sources are required - one called “Fertilizer Nitrogen” and the other called “Fertilizer Phosphorous”.

The input data must be a polygon shape file with field(s) in the associated attribute table representing the amount of fertilizer applied per polygon (e.g. farm, district or county). Data may be available from agricultural organisations, governmental institutions or statistical publications.

UnitThe units available for the fertilizer source type include kg/s, µg/s, mg/s, g/s, kg/h, kg/day, and kg/year.

ComponentsAvailable components for the fertilizer source type are:

Ntot - Total Nitrogen

NH4 - Ammonia-Nitrogen

NO3 - Nitrate-Nitrogen

Ptot - Total Phosphorous

User Def - User defined substance

Livestock Sources The Livestock Source type typically represents pollutants derived from manure or slurry from cattle, hogs, sheep, horses, poultry, etc.

For each livestock source several different types of pollutants can be spec-ified via the Source Load per Head button. This button opens the Load Source Fluxes Editor (p. 63). For each pollutant component a value must be specified representing the average production or field application of

58 MIKE BASIN

Sources

manure or slurry, e.g. kg N /year/cow. Available components for livestock sources are:

BOD- Biological Oxygen Demand

Ntot- Total Nitrogen

NH4- Ammonia-Nitrogen

NO3- Nitrate-Nitrogen

Ptot- Total Phosphorous

EColi- E-Coli Bacteria

User Def- User defined substance

Input data must be a polygon shape file with field(s) in the associated attribute table representing the number of heads per polygon (e.g. farm, district or county). Data may available from agricultural organisations, governmental institutions or statistical publications.

Domestic Sources The Domestic Source typically represents pollutants deriving from human settlements, for example sewage and waste water from households. Sev-eral domestic sources can be specified reflecting different types of popula-tions, such as urban and rural populations, sewered and non-sewered populations, that may differ with respect per capita loadings.

For each domestic source several different types of pollutants can be spec-ified via the Loads per Capita button. This button opens the Load Source Fluxes Editor (p. 63). For each pollutant, a per capita load must be speci-fied representing the average production or contribution per person per time unit, e.g. kg BOD/cap/year. Available components for domestic sources are:


Ntot- Total Nitrogen

NH4- Ammonia-Nitrogen

NO3- Nitrate-Nitrogen

Ptot- Total Phosphorous

EColi- E-Coli Bacteria

User Def- User defined substance

59

Load Calculator

Input data must be a polygon shape file with field(s) in the associated attribute table representing the number of persons per polygon (e.g. dis-trict, region or statistical enumeration blocks). Data are often available from statistical departments or publications.

Treatment efficienciesThe treatment efficiencies must be specified as a dimensionless number. The number can vary in space by assigning different treatment efficiencies to different polygons (~administrative or statistical units). For details on how to interpret and apply treatment efficiencies see the Treatment Effi-ciencies Editor (p. 64)

Point Sources Point Sources typically represents pollutant sources with a well defined outlet location such as industries, waste water treatment plants, urban cen-tres, individual households and other types of individual sewage outlets. Any number of Point sources can be specified reflecting different types of point sources.

For each point source only one pollutant can be specified. If multiple pol-lutants must be defined for a particular point source, separate point sources must be defined. For example, four point sources might be “Indus-try Nitrogen”, “Industry Phosphorous”, “Industry BOD”, Industry Deter-gent”.

Input data must be a point shape file with field(s) in the associated attribute table representing the amount of pollutant discharged per point (e.g. individual industry, household, urban centre, WWTP). Data may be available from statistical departments, publications, environmental agen-cies or local authorities.

UnitThe units available for the fertilizer source type include kg/s, µg/s, mg/s, g/s, kg/h, kg/day, and kg/year.

ComponentsAvailable components for the fertilizer source type are:


Ntot - Total Nitrogen

NH4 - Ammonia-Nitrogen

NO3 - Nitrate-Nitrogen

60 MIKE BASIN

Sources

Ptot - Total Phosphorous

User Def - User defined substance

Land Use Source EditorLand use specific pollutant loading is not available as an explicit option but can be specified using the Livestock source type (see Livestock Sources (p. 58)).

The input data must be a polygon theme land use map. In the attribute table, instead of one field representing all the land use types, one field must to be defined for each land use type. The area of the polygon (e.g. km2 or ha) must be specified (or calculated) for each record belonging to the land use type represented by the field. Values in all other records must be zero

Only one Land use category can be specified for each Livestock Source Type. Land use specific loads are then specified by opening the Load Source Fluxes Editor by clicking the Loads per head button (see Live-stock Sources (p. 58)). Instead of loads per head, the values must represent area specific loads, e.g. kg BOD/year/ha or kg N/year/km2.

6.1.5 Runoff Coefficients EditorThe runoff coefficients must be specified as a dimensionless number and can be applied to Fertilizer and Livestock Source Types (p. 61) and Point Source Types (p. 62).

Fertilizer and Livestock Source TypesThe runoff coefficients for Fertilizer and Livestock Sources can vary in space by assigning different runoff coefficients to different polygons (e.g. administrative or statistical units). The fraction can be interpreted in two different ways depending on whether Distance Decay (p. 66) is included or excluded.

With Distance DecayWhen distance decay is included, the runoff coefficient may represent a fraction of the applied fertilizer or manure that is leaching from the top soil after application. This fraction can be estimated by performing a sim-ple mass balance, e.g. by estimating the amount of fertilizer or manure that is removed by harvest, immobilised in the soil, evaporated or degraded through microbial activity. The residue can be assumed to be available for leaching and eventually transported through the catchment to the river net-work via surface runoff, drainage or groundwater. While the runoff coeffi-cient describes the “excess” nutrient or pollutant in the top soil, the distance decay describes the retention of the pollutants during transport.

61

Load Calculator

This ensures that the sources closest to the river network contribute more than those further away.

Without Distance DecayIf distance decay is not included, the runoff coefficient reflects both the leaching of the pollutant from the top soil, as well as the retention during transport of the pollutants to the river network. This method will not con-sider the spatial distribution of the pollutant sources, unless runoff coeffi-cients are gradually reduced depending on the distance of the polygon from the MIKE BASIN/MIKE 11 river reaches.

Point Source TypesThe runoff coefficients for point sources can vary in space by assigning different runoff coefficients to different points (e.g. industries, WWTPs, households or urban centres). Since point source loads are often dis-charged directly into the river network, runoff coefficients may not have to be specified (i.e. values set to 1). However, if the point sources represent, for example, individual households with different types of retention tanks or sewage outlets, the runoff coefficient may be applied to reflect different retention efficiencies of the different systems. Since pollution load data are often of varying quality runoff coefficients may also be applied as sim-ple calibration factors adjusting loads where pollutant loads may not com-ply with river water quality measurements.

The fraction can be interpreted in two different ways depending on whether Distance Decay (p. 66) is included or excluded. By including dis-tance decay, the decay and/or retention of pollutant during the transport from the point source to the outlet in the river network is included as part of the distance decay function. If distance decay is not included, the runoff coefficient must also represent the decay and/or retention during transport.

Editor for the Runoff Coefficients TableThe Runoff Coefficient table includes the following fields:

District - The ID/Name corresponding to the ID/Name field specified for the Load Source

BODReductionFactor - factor between 0 and 1 for BOD

NTotReductionFactor - factor between 0 and 1 for Total Nitrogen

NH4ReductionFactor - factor between 0 and 1 for Ammonia

NO3ReductionFactor - factor between 0 and 1 for Nitrate

PTotReductionFactor - factor between 0 and 1 for Total Phosphorous

62 MIKE BASIN

Sources

EColiReductionFactor - factor between 0 and 1 for E-Coli bacteria

UserDefReductionFactor - factor between 0 and 1 for User Defined pollutant

6.1.6 Load Reduction Factors EditorSee Treatment Efficiencies Editor (p. 64).

6.1.7 Load Sources Table The Load Sources Table is opened from the View Table button on the Sources (p. 55) section of the Load dialogue. This table summarizes the key properties of all the specified pollution sources. This table cannot be edited.

The Load Sources Table includes the following fields:

SourceName - The Name of the sources.

SourceType - The source type (livestock, fertilizer, domestic or point)

SourceCategory - The source category (Agriculture, Domestic or Point)

BaseValueFeatureClass - The feature class input file name

BaseValueField - The input field in the feature class attribute table

DistrictNamefield - The Unique identifier field

TemporalVariabilityTS - The alpha time series dfs0 file

ModulateByRunoff - Loads modulated by rainfall runoff, True/false

UseReduction - True/false,

As well as the pollutant parameters for BOD, NTot, NH4, NO3, PTot, EColi, and User Defined.

6.1.8 Load Source Fluxes Editor The Load Sources Fluxes Editor is accessed through the Livestock Sources (p. 58) and Domestic Sources (p. 59) items. The table stores val-ues for per unit loads for domestic and livestock sources.

For each pollutant to be included in the calculation, a value and a unit must be specified. Values are set by typing a number in the field and the unit is specified by selecting a unit from the scroll down menu, e.g. kg/year, kg/s or g/day.

The Load Sources Fluxes Editor table includes the following fields:

63

Load Calculator

SourceName - The name of the pollution source

BODValue - The per unit load for BOD

BODUnit - The unit for per unit load for BOD

NTotValue - The per unit load for Total Nitrogen

NTotUnit - The unit for per unit load for Total Nitrogen

NH4Value - The per unit load for Ammonia Nitrogen

NH4Unit - The unit for per unit load for Ammonia Nitrogen

NO3Value - The per unit load for Nitrate Nitrogen

NO3Unit - The unit for per unit load for Nitrate Nitrogen

PTotValue - The per unit load for Total Phosphorus

PTotUnit - The unit for per unit load for Total Phosphorus

EColiValue - The per unit load for E-Coli

EColiUnit - The unit for per unit load for E-Coli

UserDefValue - The per unit load for User Defined pollutant

UserDefUnit - The unit for per unit load for User Defined pollutant

6.1.9 Treatment Efficiencies Editor The Treatment Efficiencies Editor is accessed through the Domestic Sources (p. 59) item. Treatment efficiencies for domestic sources can vary in space by assigning different treatment efficiencies to different poly-gons. Values must between 0 and 1, with 0 representing no retention and 1 representing complete retention. Treatment efficiencies can be specified to reflect the spatial variation of the waste water treatment facilities or types of sewage tanks used.

The Treatment Efficiencies Editor table include the following fields for data input.

District - The ID/Name corresponding to the ID/Name field specified for the Load Source

BODReductionFactor - factor between 0 and 1 for BOD

NTotReductionFactor - factor between 0 and 1 for Total Nitrogen

NH4ReductionFactor - factor between 0 and 1 for Ammonia

NO3ReductionFactor - factor between 0 and 1 for Nitrate

PTotReductionFactor - factor between 0 and 1 for Total Phosphorous

64 MIKE BASIN

Transport

EColiReductionFactor - factor between 0 and 1 for E-Coli bacteria

UserDefReductionFactor - factor between 0 and 1 for User Defined pollutant

6.2 Transport

In the Transport section of the dialogue, values are specified related to the transport and retention of pollutants. This includes three tabs:

A General Tab,

A Distance Decay Tab, and

A MIKE 11 Links Tab

6.2.1 General TabFor each sub-catchment in the MIKE BASIN Catchment feature class, total loads will be calculated for each pollutant included in the Sources specifications.

Import CatchmentsIn some cases the Load Calculator will be used without setting up a full MIKE BASIN network including river reaches, nodes and catchments and instead using an external polygon shape file. This way the Load Calculator can be used as a stand alone tool for calculating annual loads or for pro-viding input for MIKE 11.

.

Clicking on the “Import Catchments...” button will open the Import Fea-tures dialogue where the “Import From Feature Class” and the “DHI Net-work Feature Class” must be specified. The latter refers to the “empty” Catchment feature class automatically generated when starting a new MIKE BASIN project in a new GeoDatabase.

65

Load Calculator

Optionally the import can include “Shapes only” or include “Shapes and non-duplicate fields” if additional information needs to be included in the Catchment feature class attribute table.

By enabling the “Import selected features only” only actively selected fea-tures will be imported.

Catchment Properties...The Catchment Properties button launches the Load Catchment Properties Editor (p. 73), where a number of settings relevant for pollutant transport must be specified.

6.2.2 Distance Decay Note: Distance decay is only available if Spatial Analyst has been installed.

The Distance Decay functionality is a raster based tool for including dis-tance dependant retention of pollutants. The assumption is that the amount of pollutants reaching the river depends on the transport distance, i.e. the sources closest to the river contribute the most pollutant. Distance decay is calculated as a simple first-order distance specific retention

(6.1)

where mriver is the loads from a sub-catchment reaching the river (mass flux), Σmload is the sum of loads generated by each cell within a subcatch-ment, K is the first-order decay rate in the runoff (e.g. km-1), D is the dis-tance from location of the cell to the nearest downstream point (e.g. km), G is the gradient of the slope (e.g. m/m) and T is the average temperature in degrees Celsius.

The slope dependency assumes that retention/decay increases with decreasing slope due to a resulting slower flow velocity. Input data includes two raster themes, a distance grid, where each cell value indi-

mriver Σ mload e⋅K D 1

G---- 1,05⋅

T 20–⋅ ⋅–

=

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cates the distance to the river (e.g. in kilometres), and a gradient grid, where each cell value indicates the slope in dimensionless units. Both grids can be created by the standard functions in Spatial Analyst.

Note: Both grids must be identical in extent and cell size.

Ideally, the gradient for the cell should be calculated as the difference in elevation between the cell and the river where water from the cell will flow to, divided by the flow distance. In practice, an average catchment slope can be used, or a constant gradient of 1 can be used, to remove this term from the equation. In each case, decay rates can be adjusted to cali-brate the decay.

When including distance decay, several raster grids will be added to the Table of Contents after the calculation. The number of grids depends on the number of pollutants and source types (i.e. Non-point, Domestic and Point sources) included in the load calculation. One grid is generated for each combination of pollutant and source type. Each grid summarizes the total load (mass flux in e.g. kg/year) per cell. The total loads per cell repre-sent the loads after the distance decay has been added.

Distance Decay Dialogue

Use distance decay - To include Distance Decay check the “Use distance decay” check box.

Gradient grid - Select the grid theme for the gradient. Only grid themes available in the Table of Contents can be selected. The gradient grid can be generated using the standard functions in Spatial Analyst.

Distance grid - Select the grid theme for the distance to the river. The dis-tance grid can be generated using the standard function in Spatial Analyst.

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Detailed grid output - By checking the “Detailed grid output” check box additional grids will be generated and added to the Table of Contents including all combination of pollutant components and Load sources.

Decay Rates... - This button launches the Decay Rates Editor (p. 76), where decay rates are specified for each combination of pollutant compo-nents and each of the three pollution source categories (i.e. non-point, domestic and point).

6.2.3 MIKE 11 LinksThe Load Calculator can automatically create boundary conditions for a Mike 11 Water Quality simulation.

To correctly calculate inflow concentrations, the Load Calculator needs to know the amount of runoff in the system. Therefore, you need to first run the flow model using the rainfall-runoff module in Mike 11, or a coupled Mike SHE-MIKE 11 model. Then import the runoff results before running the Load Calculator.

Since the MIKE 11 load components (the solutes and bacteria) can be defined in an Ecolab file or an AD parameters file, you need to define which components in the Load Calculator correspond to those in Mike 11.

The above leads to the following four steps when creating Water Quality boundary conditions for MIKE 11 using the Load Calculator:

1 Specify the Mike 11 Model

2 Import the Runoff Results,

3 Assign Load Components, and

4 Use the Results in MIKE 11

Specify the Mike 11 Model Step One is to specify your Mike 11 setup. The same MIKE 11 setup must be used for both the rainfall runoff results and the water quality simula-tion.

1 Click on the “Mike 11" check box in the Output section to enable the Mike 11 Links tab.

2 On the Mike 11 Links tab, use the browse button to select the .sim11 file for your Mike 11 setup.

The Load Calculator will automatically find the .nwk11, .bnd11, and any Ecolab or .ad11 files referenced in your Mike 11 setup

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.

Import the Runoff Results Step Two is to import the runoff results:

1 Select either the “Rainfall Runoff Links”, if you used the Rainfall-Run-off module in Mike 11, or the Mike SHE coupled model, if you used Mike SHE to calculate inflow.

2 Then click on the “Import Results” button.

Depending on the option you selected above, the results will be imported in two different ways.

Importing MIKE 11 Rainfall-Runoff Results In MIKE 11, Rainfall-Runoff is calculated using the same NAM model as that in MIKE BASIN. This makes the importing of MIKE 11 NAM results relatively straight forward, because the MIKE 11 NAM catchments are simply mapped directly to the LOAD catchments. The only requirement is that the MIKE 11 NAM catchment names are the same as the LOAD Cal-culator catchment names.

During the import, for each MIKE 11 NAM catchment, the Load Calcula-tor

1 reads the overland flow, interflow, and baseflow time series from the MIKE 11 NAM result file,

2 creates a new, total baseflow time series file (_totalbaseflow.dfs0) that sums the two MIKE 11 NAM baseflow components, and

3 adds references to the overland flow, interflow and total baseflow files in the Catchment Properties table.

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The Load Calculator uses the Temporal Analyst data tables to keep track of the file locations and data types, so the time series will be added to the “Time Series” tab in the ArcMap Table of Contents, just as all other time series used by the Load Calculator.

Note: The time series are added to the catchment properties table in the same way as the MIKE BASIN NAM results are added when run from inside ArcMap. In principle, you could chose to run the NAM module in ArcMap directly, but we do not recommend this. If you do choose to run the NAM model from ArcMap directly, your NAM catchment names and the inflow results must be the same as in your Mike 11 setup, or you will end up with mass balance errors.

Importing MIKE SHE Results When importing Mike SHE results, the Load Calculator does several things:

1 The result file is examined and all inflow results which discharge to the Mike 11 network are extracted and rewritten to the disk as dfs0 files. A separate file is created for each inflow point. Each file has four items: overland flow, drain flow, base flow, and total flow, which is the sum of the first three. These files are written to a new subdirectory in the same directory where the Mike 11 boundary (.bnd11) file is located. The name of the directory is SHEResultName_InflowTS where SHEResultName is the name of the Mike SHE result file.

2 For each inflow point, a new inflow boundary conditions is added to the MIKE 11 .bnd11 file. Each MIKE 11 inflow boundary condition will have three point source boundary conditions: one for overland flow, one for drain flow, and one for total base-flow. Each point source boundary condition will reference the time series items extracted in the previous step. Note, the boundary conditions will only be used for AD boundaries not HD boundaries.

3 The Mike 11 network file is imported as a feature layer in the map. The branch coordinates and chainage values (called measures in ArcGIS) are read from the MIKE 11 .nwk11 file.

4 Each of the inflow points is georeferenced (i.e. the geographic coordi-nates are calculated) by looking up the branch and chainage of the inflow point and finding their location along the branches imported in the previous step. User and system points are taken into account to cor-rectly interpolate locations along the branch. A new feature layer is added to the map with the inflow points.

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Assign Load ComponentsMike 11 is very flexible in modelling water quality components, and with the Ecolab module, you can even define your own components. Since the Load calculator has a fixed set of components, you need to identify which of the Mike 11 components correspond with the fixed set of Load compo-nents. Clicking on the Set Components... button opens the following dia-logue

On the left are the Load Calculator components. On the right are combo boxes listing all the components defined in the Mike 11 setup. If an Ecolab file has been defined, the combo boxes will list the components defined in the Ecolab file, otherwise the combo boxes will list the components in the MIKE 11 .ad11 file. You must have at least one of these two files refer-enced in your .sim11 file. Select the Mike 11 component that corresponds to each of the Load Calculator components on the left. You do not need to assign all components - only those that are actually being used in the Load Calculator.

Note You can be quite liberal in making these assignments, since the Load Calculator treats all components, except Total Nitrogen, the same. Total nitrogen is split by a user-specified fraction, into ammonia and nitrates.

Use the Results in MIKE 11When you run the Load Calculator to calculate Mike 11 Water Quality boundary conditions, the Load Calculator will calculate the loads for each catchment as usual. It will then generate time series for each component and add them to the Mike 11 boundary file. The exact method is deter-mined by the inflow option selected in the Mike 11 Links tab.

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Output for Mike 11 Using MIKE 11 Rainfall-Runoff LinksIf you are using rainfall-runoff links, the total average runoff for each catchment is calculated from the imported runoff results. If you have spec-ified a runoff period in the catchment properties, only this period will be considered. The non-point agricultural loads (sources of type fertilizer or livestock) are divided by the average runoff to calculate an average con-centration. The output time series will match the alpha time series speci-fied in the load sources. The output concentrations will be adjusted according to the alpha values.

Warning If you set any alpha values different than 1.0 for agricultural sources, you will likely get mass balance errors. We recommend that you only use alpha values equal to 1.0 for agricultural sources.

The Load Calculator will then add these concentration time series to the Mike 11 boundary file as distributed source boundary conditions linked to the same branch and chainages as the rainfall-runoff links specified in the .nwk11 file for each catchment. The boundaries will be set as AD-RR boundary conditions. A separate boundary is added for each runoff com-ponent (overland flow, interflow, and baseflow). For baseflow, a constant concentration is added equal to the baseflow concentration specified for each catchment in the catchment properties.

The domestic and point source loads are calculated as fluxes (mass per unit time) and adjusted by the alpha values (to maintain mass balance, alpha values must have a time-weighted average of 1.0). These time series are also added to the Mike 11 boundary file as distributed sources accord-ing to the rainfall-runoff links specified in the .nwk11 file. Each flux time series is divided according to the fraction of the area specified in each rainfall runoff link to the total area of the catchment. Thus the total flux for each catchment is maintained. The fluxes are converted to concentra-tions and added with a constant discharge equal to one cubic meter per second. However, the boundary condition is set to include AD boundaries only, not HD calculations. The load is then effectively treated as a “dry” flux in Mike 11.

All new boundary conditions are labelled with a boundary ID in the form [Load: <Source Type>], where the source type is either non-point or domestic/point source. Non-point boundaries also include the runoff com-ponent in the label (overland, interflow, or baseflow.)

Output for Mike 11 using Mike SHE InflowsFor the Mike 11 setup with Mike SHE inflows, the non-point agricultural load concentrations are calculated in the same way as for the rainfall run-off links (see previous section). However, the average total runoff for each

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catchment is calculated by adding the discharge at all inflow points in the catchment. When the Load Calculator is run, it relies on calculating the average total runoff based on the inflow locations and inflow boundary conditions added when the Mike SHE results were imported. As with the rainfall runoff links, baseflow concentrations are added as constant values as specified in the catchment properties. Since the inflow boundary condi-tions were already added to the Mike 11 boundary file during import, the non-point loads components are simply added to the existing boundary conditions.

For domestic sources, the flux time series are also calculated in the same manner as for the rainfall runoff links (see previous section). However, the total flux for the catchment is divided equally among all inflow points in the catchment.

All boundary conditions added by the Load Calculator are labelled with a boundary ID in the form [Load: <Source Type>], [Load: <Source Type>], where the source type is either non-point or domestic/point source. Non-point boundaries include the runoff component in the label (overland, drain, or baseflow.)

6.2.4 Transport EditorsTransport editors include

the Load Catchment Properties Editor (p. 73), which is only relevant when MIKE BASIN output (p. 79) or MIKE 11 output (p. 79) has been selected, and

the Decay Rates Editor (p. 76), which is only relevant when Distance Decay (p. 66) has been included.

Load Catchment Properties Editor This editor is only relevant when the MIKE BASIN output (p. 79) or MIKE 11 output (p. 79) has been selected in the Output (p. 77) section of the Load dialogue.

The Load Catchment Properties table includes settings relevant for the transport of pollutant. Three types of settings are available:

Runoff Start and End Time (p. 74)

NH4 - Fraction (p. 74), and

Baseflow concentrations (p. 74).

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Runoff Start and End TimeFor non-point sources, pollutant transport to the river (as a flux) is typi-cally positively correlated with the Rainfall runoff. Non-point sources include all sources specified as Livestock or Fertilizer source types. To account for this runoff dependent flux of non-point pollutants, it is assumed that pollutant concentrations in the runoff are constant.

The Runoff Start and End time is applied to specify a period for which annual non-point loads (e.g. kg/year) are translated into an average pollut-ant concentration (e.g. mg/l). The total annual load (i.e. total mass) is divided by the total accumulated runoff (i.e. total volume) for the speci-fied period to calculate the mean runoff concentration (e.g. in mg/l) of each pollutant originating from non-point sources. To provide a variable load flux input time series for MIKE BASIN, this concentration is then multiplied by the runoff time series specified for each Catchment in the MIKE BASIN setup.

For details on exact mathematical expression, see the MIKE BASIN refer-ence manual.

Typically, the period specified will be of one year duration and represent the calibration period for a MIKE BASIN Water Quality model.

If the assumption of a constant concentration of a pollutant in the runoff originating from non-point sources is not satisfactory, it is possible to apply an alpha time series to distribute the non-point sources in time (see Time distribution (alpha time series) (p. 57)).

NH4 - FractionIf Total Nitrogen has been specified as one of the pollutant components in at least one of the pollution sources, a NH4 - Fraction must be specified indicating the expected fraction of Total Nitrogen that constitutes ammo-nia-nitrogen. The remaining fraction is defined as nitrate-nitrogen.

Baseflow concentrationsThis option is only relevant if a groundwater runoff component has been explicitly included in the setup of the MIKE BASIN Water Balance model. This must be included as separate time series files, either as a user specified time series or as a NAM model simulation result (see the MIKE BASIN Runoff section).

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When a ground water component is included as described above, only the fraction of the total load corresponding to:

(Total Runoff - Groundwater runoff)/Total Runoff (6.2)

will be added to the MIKE BASIN catchment node in the river network. The rest of the loads are ignored. Instead a user specified base flow con-centration must be specified for each pollutant component representing the expected pollutant concentration in the groundwater discharging into the river section. Base flow concentrations can be identified from water quality measurements as concentrations found during low flow situations in parts of the river where domestic and point sources are absent. Thus, the base flow concentration is often a calibration parameter.

This approach has been introduced based on the assumption that most non-point loads are derived from the overland or drainage flow compo-nents of the hydrological cycle. This is often seen in rivers dominated by non-point sources resulting in a high concentration of pollutants during high flow and low concentrations during low flow. The fluctuation of con-centrations in this case is typically determined by the relation between groundwater and surface/drainage water discharge to the river. Base flow concentrations are typically considerably lower (e.g. <10 %) in base flow compared to in surface/drainage flow.

In some cases, though, transport through ground water may be significant. In those situations it may be recommended not to include groundwater separately as describe above. Instead use the Distance Decay (p. 66) func-tion to describe the overall retention of pollutants in the total runoff not distinguishing between different types of runoff components.

Load Catchment Properties TableThe Load Catchment Properties table includes the following fields:

Name - The name of each of the Catchments in the “Name” field spec-ified in Transport General Dialogue.

WQRunoffStartTime - Start date for a period for calculating mean non-point concentration

WQRunoffEndTime - End date for a period for calculating mean non-point concentration

WQFractionNH4 [-] - Fraction of Total Nitrogen constituting Ammo-nia - Nitrogen

WQBaseflowConcBOD [mg/l] - Concentration of BOD in Base Flow

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WQBaseflowConcNH4 [mg/l] - Concentration of Ammonia in Base Flow

WQBaseflowConcNO3 [mg/l] - Concentration of Nitrate in Base Flow

WQBaseflowConcPtot [mg/l] - Concentration of Total Phosphorous in Base Flow

WQBaseflowConcEColi [M/100 ml] - Concentration of E-Coli in Base Flow

WQBaseflowConcUserDef [mg/l] - Concentration of User Defined component in Base Flow

Decay Rates Editor In the Decay Rates Editor, all distance specific decay rates are specified. For details on the conceptual approach, see the Distance Decay (p. 66) section. First-order decay rates can be specified for all combinations of each pollutant and each of the three categories of pollution sources (i.e. non-point, domestic and point).

The Decay Rates table includes the following fields:

LoadCategory - Load source categories

BODOverlandDecayRate - first-order distance specific decay rate for BOD

NTotOverlandDecayRate - first-order distance specific decay rate for Total Nitrogen

NH4OverlandDecayRate - first-order distance specific decay rate for Ammonia-Nitrogenfirst-order

NO3OverlandDecayRate - first-order distance specific decay rate for Nitrate-Nitrogen

PTotOverlandDecayRate - first-order distance specific decay rate for Total Phosphorus

EColiOverlandDecayRate - first-order distance specific decay rate for Total E-Coli bacteria

UserDefOverlandDecayRate - first-order distance specific decay rate for User Defined Pollutant

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Output

6.3 Output

In the Output section of the Load dialogue, there are three output check boxes for selecting different types of output

.Maps and Statistics output (p. 77) for output in tables directly related to the Catchment attribute table,

MIKE BASIN output (p. 79) for output to be used as input to the MIKE BASIN WQ module, and

MIKE 11 output (p. 79) for output to be used as input to the MIKE BASIN 11 ECO Lab module

6.3.1 .Maps and Statistics outputTo include Maps and Statistics as calculation output, check the Maps and Statistics checkbox. Table output will be presented in a Load Result table. For each WQ component included in the sources specifications total loads will be divided into Non-point (i.e.Livestock Sources and Fertilizer Sources types), Domestic and Point loads. In addition the non-point load fraction an average concentration of non-point derived sources are calcu-lated reflecting the predicted concentration of the pollutant in the total runoff (or drainage water/overland flow if Baseflow concentrations (p. 74) are explicitly included).

xxTotal - Total loads (e.g. kg/year) for WQ component “xx”

xxNonpoint - Non-point loads (e.g kg/year) for WQ component “xx”

xxDomestic - Domestic loads (e.g kg/year) for WQ component “xx”

xxPoint - Point loads (e.g kg/year) for WQ component “xx”

xxConc - Calculated average concentration (e.g. mg/l) of non-point sources in runoff concentrations for WQ component “xx”

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When including baseflow in the Load calculation, only the fraction of the total loads corresponding to:

(Total Runoff - Groundwater runoff)/Total Runoff

will be included in the non-point and total load fraction in the Load Results table. Loads originating from baseflow (e.g. baseflow discharge times the baseflow concentration specified in the Catchment properties dialogue) will be added to the non-point and total load fractions.

The data in the Load Results table is stored in the Catchment feature class table and it is possible to produce chart maps displaying loads per catch-ment using the standard plot facilities in ArcMap. To access the Load Result fields in the Catchment feature class, right click on the Catchment layer in the ArcMap TOC and in the Fields section of the Layer Properties dialogue select the fields you wish to make visible and thereby accessible for changing the layer symbology of the Catchment layer:

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Output

6.3.2 MIKE BASIN outputIf the MIKE BASIN output option is selected, a dfs0 time series file for each MIKE BASIN Catchment will be generated. Each time series file includes items corresponding to the total number of pollution sources included in the load calculation. For each pollution item, the values repre-sent the total mass flux in kg/s. The dfs0-files are automatically assigned to each of the MIKE BASIN sub-catchments (see the MIKE BASIN Water Quality section of the manual).

6.3.3 MIKE 11 outputIf the load results are to be used together with at MIKE 11 (e.g. with a NAM or ECOLab model setup), the catchment theme specified in General Tab (p. 65) tab must be equivalent to the NAM catchment applied in the NAM model. The output consists of two dfs0 time series files for each catchment representing the non-point and point fractions respectively.

Each time series file includes a number of items corresponding to the total number of pollution sources included in the load calculation. For each pol-lutant, the values represent the total mass flux in kg/s (or count/day for bacteria).

The output time series can be used in the MIKE 11 boundary editor as input to the MIKE 11 solute transport model. (see the MIKE 11 AD user manual for details).

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80 MIKE BASIN

NAM Overview Tab

5 NAM RAINFALL-RUNOFF Rainfall-runoff modelling is a pre-processing step in MIKE BASIN that creates the runoff time series for the individual catchments. Simulations of MIKE BASIN is done subsequently. Running the rainfall-runoff model will create input catchment runoff time series files for all the specified catchments. MIKE BASIN is then executed normally. For MIKE 11 appli-cations it is preferable to use MIKE 11 RR, but the rainfall-runoff module in MIKE 11 GIS can be used and is therefore described in this chapter.

The NAM model is a deterministic, lumped and conceptual Rainfall-run-off model accounting for the water content in up to four different storages. NAM can be prepared in a number of different modes depending on the requirement. As default, NAM is prepared with nine parameters represent-ing the Surface zone, Root zone and the Ground water storages. In addi-tion NAM contains provision for:

– Extended description of the ground water component.

– Two different degree day approaches for snow melt.

The NAM Rainfall-Runoff component is accessed from the Toolbar, under the MIKE BASIN/MIKE 11 menu.

Rainfall-Runoff tables are available for specifying parameters for the

Surface-Rootzone,

Groundwater, and

Snowmelt.

These parameters are specified for each representative catchment. Tables are also available for specfiying initial conditions and cross-references to each of the above reference catchments for each of the MIKE BASIN catchments that require rainfall-runoff modeling.

The NAM Rainfall-Runoff simulation does not have to cover the same period as the MIKE BASIN simulation.

Parameters for all options are described in the following sections.

5.1 NAM Overview Tab

In the NAM Overview tab, there are two buttons along the top and a table of common attributes for each of the defined catchments. If you have

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NAM Rainfall-Runoff

installed other DHI Software products there may be additional buttons available. The individual Parameters are listed in the following subsection

.

5.1.1 Parameters

Catchment Name (Name)Simulations can be carried out for several catchments at the same time. The catchment name corresponds to the name of the catchment given in the Catchment Properties Dialog. See Catchment Properties.

Model type (ModelType)The parameters required for each Rainfall-Runoff model type are speci-fied in separate tables. Following models can be selected:

1 LOAD WQ

2 ICM WQ, 1-Layer GW

3 ICM WQ, 2-Layer GW

4 NAM RR, 1-Layer GW

5 NAM RR, 2-Layer GW

6 NAM RR, 1-Layer GW, LOAD WQ

7 NAM RR, 2-Layer GW, LOAD WQ

8 1-Layer GW

Catchment Area (AssignedArea)The default area shown for each catchment corresponds to the area given in the catchment Properties Dialog. The area can be modified as neces-sary.

(NAMSurfRootID)The name of the reference catchment type with a corresponding set of the Surface- Rootzone parameters. See TS Weights Button (p. 44).

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NAM Overview Tab

(NAMGroundwaterID)The name of the reference aquifer type with a corresponding set of Groundwater parameters. See Ground Water Tab (p. 46).

(NAMSnowMeltID)The name of the reference snowmelt condition type with a corresponding set of Snowmelt parameters. See Snow Melt Tab (p. 47).

(NAMInitCondID)The name of the reference initial conditions type with a corresponding set of initial conditions. See Initial Conditions Tab (p. 49).

Rainfall (RainfallTS)A time series, representing the average catchment rainfall. The time inter-val between values, may vary through the input series. The rainfall speci-fied at a given time should be the rainfall volume accumulated since the previous value.

Evapotanspiration (PotentialEvapotranspirationTS)The potential evaporation is typically given as monthly values. Like rain-fall, the time for each potential evaporation value should be the accumu-lated volume at the end of the period it represents. The monthly potential evaporation in June should be dated 30 June or 1 July.

Observed Discharge It is not necessary to specify a time series of observed discharge values here.

The selection of the observed discharge will automatically enable addi-tional output which includes a calibration plot with comparison of observed and simulated discharge and calculation of statistical values.

For calibration purposes all observed discharge time series files should be included in the databse and associated to the appropriate node for compar-ison with the simulated time series after e.g. MIKE BASIN has been run.

Temperature (TemperatureTS)A time series of temperature, usually mean daily values, is required only if snow melt calculations are included in the simulations.

Reference level for temperature station (TempRefLevel)Defines the altitude at the reference temperate station. This station is used as a reference for calculating the temperature and precipitation within

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NAM Rainfall-Runoff

each elevation zone. (The file with temperate data is specified on the time-series page).

Dry temperature lapse rate (DryTempLapseRate)Specifies the lapse rate for adjustment of temperature under dry condi-tions. The temperature in the actual elevation zone is calculated based on a linear transformation of the temperature at the reference station to the actual zone defined as the dry temperature lapse rate (C/100m) multiplied by the difference in elevations between the reference station and the actual zone.

Wet temperature lapse rate (WetTempLapseRate)Specifies the lapse rate for adjustment of temperature under wet condi-tions defined as days with precipitation higher than 10 millimetres. The temperature in the actual elevation zone is calculated based on a linear transformation of the temperature at the reference station to the actual zone defined as the wet temperature lapse rate (C/100m) multiplied by the difference in elevations between the reference station and the actual zone.

Reference level for precipitation station (PrecipRefLevel)Defines the altitude at the reference precipitation station (The file with precipitation data is specified on the timeseries page).

Correction of precipitation (PrecipCorrectRate)Specifies the lapse rate for adjustment of precipitation. Precipitation in the actual elevation zone is calculated based on a linear transformation of the precipitation at the reference station to the actual zone defined as precipi-tation lapse rate (C/100m) multiplied by the difference in elevation between the reference station and the actual zone.

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Run NAM Simulation Button

5.2 Run NAM Simulation Button

Pressing the Run Simulation button will bring up a Run NAM Simulation dialog for specifying the simulation period and desired time step. Note, that the following options are NOT currently available in MIKE BASIN:

Hot start

Force recalculation of mean area weighted time series

5.3 Select TS Button

Clicking on this button allows you to access time series files in the data base and to include them in the NAM Overview table. To edit the time series

1 Click on the edit tool button,

2 Click on the filed where the time series file should be entered,

3 Click on the Select TS button,

4 Click on the appropriate time series item,

5 Click on the Open Time Series button, and finally

6 Stop editing when you finish.

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5.4 TS Weights Button

With this button , multiple input timeseries for mean area weighted time-series can be specified.

Ex. How to define weighted rainfall TS: Catchment1: Station1*0.5 + Station2*0.25

1) Start editing in the NAM overview table and select the cell RainfallTS.

2) Press “TS Weights...”button. It opens a new tab.

Give unique numbers for DHI ID.

When complete timeseries for all stations are available for the entire period of interest, only one weight combination is required. When data are missing at one or more stations, different combinations can be specified. In the picture, only one combination is specified.

Select TS at Time Series ID. The sum of the weight is not necessary to be one.

3) Do the same process for the other cathcment. The catchemnt can be selected from the drop-down-list.

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NAM Surface-Rootzone Tab

5.5 NAM Surface-Rootzone Tab

5.5.1 Parameters

Catchment type name (Name)This is the reference type for which a set of the Surface-Rootzone parame-ters are used.

Maximum water content in surface storage (Umax)Represents the cumulative total water content of the interception storage (on vegetation), surface depression storage and storage in the uppermost layers (a few cm) of the soil. Typically values are between 10 - 20 mm.

Maximum water content in root zone storage (Lmax) Represents the maximum soil moisture content in the root zone, which is available for transpiration by vegetation. Typically values are between 50 – 300 mm.

Overland flow runoff coefficient (CQOF)Determines the division of excess rainfall between overland flow and infiltration. Values range between 0.0 and 1.0

Time constant for interflow (CKIF)Determines the amount of interflow, which decreases with larger time constants. Values in the range of 500-1000 hours are common.

Time constants for routing overland flow (CK1_2)Determines the shape of hydrograph peaks. The routing takes place through two linear reservoirs (serial connected) with the same time con-stant (CK1=CK2). High, sharp peaks are simulated with small time con-stants, whereas low peaks, at a later time, are simulated with large values of these parameters. Values in the range of 3 – 48 hours are common.

Root zone threshold value for overland flow (TOF) Determines the relative value of the moisture content in the root zone (L/Lmax) above which overland flow is generated. The main impact of TOF is seen at the beginning of a wet season, where an increase of the parameter value will delay the start of runoff as overland flow. Threshold value range between 0 and 70% of Lmax, and the maximum values allowed is 0.99.

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NAM Rainfall-Runoff

Root zone threshold value for inter flow (TIF)Determines the relative value of the moisture content in the root zone (L/Lmax) above which interflow is generated.

5.6 Ground Water Tab

For most NAM applications only the Time constant for routing baseflow CKBF and possibly the Rootzone threshold value for ground water recharge TG need to be specified and calibrated. However, to cover also a range of special cases, such as ground water storages influenced by river level variations, a number of additional parameters can be modified.

The individual Parameters are listed in the following subsection.

5.6.1 Parameters

Root zone threshold value for ground water recharge (TG)Determines the relative value of the moisture content in the root zone (L/Lmax) above which ground water recharge is generated. The main impact of increasing TG is less recharge to the ground water storage. Threshold value range between 0 and 70% of Lmax and the maximum value allowed is 0.99.

Time constant for routing baseflow (CKBF) Can be determined from the hydrograph recession in dry periods. In rare cases, the shape of the measured recession changes to a slower recession after some time. To simulate this, a second groundwater reservoir may be included, see the extended components below.

Ratio of ground water catchment to topographical (surface water) catchment area (Carea) Describes the ratio of the ground water catchment area to the topographi-cal catchment area (specified under Catchments). Local geological condi-tion may cause part of the infiltrating water to drain to another catchment. This loss of water is described by a Carea less than one. Usual value: 1.0.

Specific yield for the ground water storage (Sy) Should be kept at the default value except for the special cases, where the ground water level is used for NAM calibration. This may be required in riparian areas, for example, where the outflow of ground water strongly influences the seasonal variation of the levels in the surrounding rivers. Simulation of ground water level variation requires a values of the specific yield Sy and of the ground water outflow level GWLBF0, which may vary

46 MIKE BASIN

Snow Melt Tab

in time. The value of Sy depends on the soil type and may often be assessed from hydro-geological data, e.g. test pumping. Typically values of 0.01-0.10 for clay and 0.10-0.30 for sand are used.

Maximum ground water depth causing baseflow (GWLBF0)Represents the distance in metres between the average catchment surface level and the minimum water level in the river. This parameter should be kept at the default value except for the special cases, where the ground water level is used for NAM calibration, cf. Sy above.

Depth for unit capillary flux (GWLBF1) Defined as the depth of the ground water table generating an upward cap-illary flux of 1 mm/day when the upper soil layers are dry corresponding to wilting point. The effect of capillary flux is negligible for most NAM applications. Keep the default value of 0.0 to disregard capillary flux.

Lower base flow. Recharge to lower reservoir (Cqlow) The ground water recession is sometimes best described using two linear reservoirs, with the lower usually having a larger time constant. In such cases, the recharge to the lower ground water reservoir is specified here as a percentage of the total recharge.

Time constant for routing lower baseflow (Cklow) Is specified for CQlow > 0 as a baseflow time constant, which is usually larger than the CKBF

5.7 Snow Melt Tab

The snow module simulates the accumulation and melting of snow in a NAM catchment. Two degree-day approaches can be applied: a simple lumped calculation or a more advanced distributed approach, allowing the user to specify a number of elevation zones within a catchment with sepa-rate snow melt parameters, temperature and precipitation input for each zone.

The simple degree-day approach uses only the two overall parameters: a constant degree-day coefficient and a base temperature.

The Snow melt module uses a temperature input time series, usually mean daily temperature.


47

NAM Rainfall-Runoff

5.7.1 Parameters

Constant Degree-day coefficient (Csnow). The content of the snow storage melts at a rate defined by the degree-day coefficient multiplied with the temperature deficit above the Base Temper-ature. Typical values for Csnow is 2-4 mm/day/C.

Base Temperature snow/rain (T0). The precipitation is retained in the snow storage only if the temperature is below the Base Temperature, whereas it is by-passed to the surface storage (U) in situations with higher temperatures. The Base Temperature is usu-ally at or near zero degree C.

Radiation coefficient (RadiationCoef)May be introduced when time series data for incoming radiation is availa-ble. The timeseries input file is specified separately on the time series page. The total snow melt is calculated as a contribution from the tradi-tional snow melt approach based on Csnow (representing the convective term) plus a term based on the radiation.

Rainfall degree-day coefficient (RainDegDayCoef)May be introduced when the melting effect from the advective heat trans-ferred to the snow pack by rainfall is significant. This effect is represented in the snow module as a linear function of the precipitation multiplied by the rainfall degree coefficient and the temperature deviation above the Base Temperature.

5.8 Elevation Zones Tab

5.8.1 Parameters

Elevation (Elevation)The elevation of each zone is specified in the table as the average eleva-tion of the zone. The elevation must increase from zone (i) to zone (i+1).

Area of the elevation zone (ZoneArea)The area of each zone is specified in the table. The total area of the eleva-tion zones must equal the area of the catchment.

Min storage for full coverage (MinStore)Defines the required amount of snow to ensure that the zone area is fully covered with snow. When the water equivalent of the snow pack falls

48 MIKE BASIN

Initial Conditions Tab

under this value, the area coverage (and the snow melt) will be reduced linearly with the snow storage in the zone.

Maximum storage in the zone (MaxStore)Defines the upper limit for snow storage in a zone. Snow above this values will be automatically redistributed to the neighbouring lower zone.

Max water retained in snow (MaxWater)Defines the maximum water content in the snow pack of the zone. Gener-ated snow melt is retained in the snow storage as liquid water until the total amount of liquid water exceeds this water retention capacity. When the air temperature is below the base temperature T0, the liquid water of the snow re-freezes with rate Csnow.

(TDryCorrect)The actual temperature correction for dry conditions to estimate actual temperature for the specific zone.

(TWetCorrect)The actual temperature correction for wet conditions to estimate actual temperature for the specific zone.

(PrecipCorrect)The relative correction for precipitatio to estimate precipitation for the specific zone.

(SnowInitial)The initial condition for snow.

(WaterInitial)The initial water content of the snow pack.

5.9 Initial Conditions Tab

The initial relative water contents of surface and root zone storage must be specified as well as the initial values of overland flow and interflow.

Initial values for baseflow must always be specified. When lower base-flow are included a value for the initial lower baseflow must also be spec-ified.

49

NAM Rainfall-Runoff

Initials values of the snow storage are specified when the snow melt rou-tine is used. When the catchment are delineated into elevation zones, the snow storage and the water content in each elevation zones are specified.


5.9.1 Parameters

Relative water content in tsurface storage (U_UMax)This is a value between zero and one, where one indicates wet initial con-dtions.

Releative water content in root zone storage (L_LMax)This is a value between zero and one.

Overland flow (QOF)The overland flow at the beginning of the simulation, which is normally based estimated from the hydrograph.

Interflow (QIF)The interflow at the beginning of the simulation, which is normally based estimated from the hydrograph.

Baseflow (BF)The baseflow at the beginning of the simulation, which is normally based estimated from the hydrograph.

Lower Baseflow (BF_low)The lower baselow at the beginning of the simulation, which is normally based estimated from the hydrograph.

Snow Storage (SnowStorage)The actual initial snow storage in mm.

5.10 Rainfall Runoff Step-by-Step (for MIKE BASIN)

1 Create a MIKE BASIN model layout as usual.

2 Specify catchment names and areas. The figure shows the Catchment Properties dialog for the largest catchment called " Large catchment". The area is 120 km2. The other catchment is called "Small catchment" and has an area of 20 km2

50 MIKE BASIN

Rainfall Runoff Step-by-Step (for MIKE BASIN)

.

3 Access the rainfall-runoff table dialogs from The MIKE BASIN tool-bar. Insert parameters for the Surface-Rootzone, Groundwater and Ini-tial conditions tables.

51

NAM Rainfall-Runoff

Note that there is no snowmelt process in this set up. The figure shows some of the parameters for the Surface-Rootzone. Also, note that the name of the catchment type that the parameters represent is called "catch".

Parameters can only be inserted after the Start Editing button has been clicked. When finished press the Stop Editing button.

4 After the parameters have been entered access the NAM Overview Table and specify the relevant data. Notice, that some of the data is pre-scribed as per specification given in the MIKE BASIN setup, ie. catch-ment names and areas. You should now enter the catchment type nameand time series files. Time sieres files must already be stored in tha data base and are inserted by pressing Select TS…

5 Click on the Run Simulation button and specify in the NAM Run dia-log the simulation period and the time set

.

6 After execution a time series file name has been inserted in time series field in the Catchment Properties dialog

52 MIKE BASIN

Rainfall Runoff Step-by-Step (for MIKE BASIN)

.

7 You can then run the MIKE BASIN for the same or another period. After running MIKE BASIN, right click on the node where you have an observed discharge series associated. The following menu will appear. You can then plot the simulated time series and subsequently click on the observed series and click on the Add to Plot button. The following plot will appear

.

8 You can the adjust the parameters and re-run the models until the com-parison is satisfactory.

53

NAM Rainfall-Runoff

54 MIKE BASIN

NAM - Introduction

19 NAM RAINFALL-RUNOFF TECHNICAL REFERENCE

This guide provides a description of aspects which are encountered during the development, calibration and application of Rainfall Runoff model, including detailed technical descriptions of the hydrological processes.

The NAM model is a lumped, conceptual rainfall-runoff model, simulat-ing the overland-, interflow, and base-flow components as a function of the moisture contents in four storages (see Section 19.1-19.9).

19.1 NAM - Introduction

The NAM hydrological model simulates the rainfall-runoff processes occurring at the catchment scale. NAM forms part of the rainfall-runoff (RR) module of the MIKE 11 river modelling system. The rainfall-runoff module can either be applied independently or used to represent one or more contributing catchments that generate lateral inflows to a river net-work. In this manner it is possible to treat a single catchment or a large river basin containing numerous catchments and a complex network of rivers and channels within the same modelling framework.

NAM is the abbreviation of the Danish "Nedbør-Afstrømnings-Model", meaning precipitation-runoff-model. This model was originally developed by the Department of Hydrodynamics and Water Resources at the Techni-cal University of Denmark (/12/),.

A mathematical hydrological model like NAM is a set of linked mathe-matical statements describing, in a simplified quantitative form, the behaviour of the land phase of the hydrological cycle. NAM represents various components of the rainfall-runoff process by continuously accounting for the water content in four different and mutually interrelated storages. Each storage represents different physical elements of the catch-ment. NAM can be used either for continuous hydrological modelling over a range of flows or for simulating single events.

The NAM model can be characterised as a deterministic, lumped, concep-tual model with moderate input data requirements. A description of the classification of hydrological models is given in Abbott and Refsgaard (1996), /2/. Refsgaard and Knudsen (1997), /14/ compare a number of dif-ferent types of hydrological model, including the NAM model, in terms of both data requirements and model performance.

211

NAM Rainfall-Runoff Technical Reference

The NAM model is a well-proven engineering tool that has been applied to a number of catchments around the world, representing many different hydrological regimes and climatic conditions.

19.2 Data Requirements

The basic input requirements for the NAM model consist of:

Model parameters

Initial conditions

Meteorological data

Streamflow data for model calibration and validation

The basic meteorological data requirements are:

Rainfall

Potential evapotranspiration

In the case of snow modelling the additional meteorological data require-ments are:

Temperature

Radiation (optional)

The NAM model also allows modelling of man-made interventions in the hydrological cycle in terms of groundwater pumping. In this case time series of groundwater abstraction rates are required.

In this section the meteorological and hydrological data are described. The model parameters and initial conditions are described in the subsequent sections.

19.2.1 Meteorological data

Rainfall (mm)The time resolution of the rainfall input depends on the objective of the study and on the time scale of the catchment response. In many cases daily rainfall values are sufficient, but in rapidly responding catchments where accurate representation of the peak flows is required, rainfall input on a finer resolution may be required. Rainfall data with any (variable) time increments can be specified in the rainfall input. The NAM model will then make the necessary interpolations according to the simulation time step. The rainfall data are treated as accumulated totals so the rainfall

212 MIKE BASIN

Data Requirements

associated with any particular time is the rainfall volume since the last entered value.

Potential evapotranspiration (mm)When daily time steps are used, monthly values of potential evapotranspi-ration are usually sufficient. In this case only minor improvements can be obtained by specifying daily values instead of monthly values. For small time steps, however, the diurnal variation of the evapotranspiration may be important. The evapotranspiration data are treated as accumulated totals where the evapotranspiration associated with any particular time is the evapotranspiration since the last entered value.

Temperature (Co)Temperature data are required if snow accumulation and melt are included in the simulations. During the snow season, the time increments in the temperature data should reflect the length of the time step in the simula-tion, e.g. daily mean temperatures. The temperature data at a given time represents the average temperature since the last entered data.

Radiation (W/m2)Actual incoming short wave radiation data can optionally be used as input in the extended snow module. The radiation data at a given time represents the average radiation since the last entered data.

Mean area weightingThe NAM model simulates the rainfall-runoff process in a lumped fashion so provision is given for combining meteorological data from different stations within a single catchment or subcatchment into a single time series of weighted averages. The resulting time series will represent the mean area values of rainfall and potential evapotranspiration for a catch-ment.

The weights are user-defined and can be determined based e.g. on the Thiessen method. In the case of missing values the weighting procedure will redistribute the weights appropriately. Therefore, it is not necessary to specify weight combinations for all possible combinations of missing sta-tions. Alternatively, the user can explicitly specify the weights when data are missing from one or more stations. A weight of “-1” is given to non-reporting stations, indicating missing data.

When rainfall data are available from stations with different reporting fre-quency, e.g. both daily and hourly stations, then the distribution in time of the average catchment rainfall may be determined using a weighted aver-age of the high-frequency stations. It is possible to use all stations to deter-

213


mine the daily mean rainfall over the catchment and subsequently use the hourly stations to distribute this daily rainfall in time. Different weight combinations for different cases of missing values may be applied also to the calculation of the distribution in time.

19.2.2 Hydrological data

Discharge (m3/s)Observed discharge data at the catchment outlet are required for compari-son with the simulated runoff for model calibration and validation. The discharge data at any particular time is the average discharge since the last entered data.

Groundwater abstraction (mm)When the effect of groundwater abstraction is expected to have a signifi-cant effect on the overall groundwater levels or catchment baseflow, pumping rates can be specified to account for these withdrawals. The groundwater abstraction data are treated as accumulated totals where the abstraction associated with any particular time is the abstraction since the last entered value.

19.3 Model Structure

A conceptual model like NAM is based on physical structures and equa-tions used together with semi-empirical ones. Being a lumped model, NAM treats each catchment as a single unit. The parameters and variables represent, therefore, average values for the entire catchment. As a result some of the model parameters can be evaluated from physical catchment data, but the final parameter estimation must be performed by calibration against time series of hydrological observations.

214 MIKE BASIN

Model Structure

Figure 19.1 Structure of the NAM model.

The model structure is shown in Figure 19.1. It is an imitation of the land phase of the hydrological cycle. NAM simulates the rainfall-runoff proc-ess by continuously accounting for the water content in four different and mutually interrelated storages that represent different physical elements of the catchment. These storages are:

Snow storage

Surface storage

Lower or root zone storage

Groundwater storage

In addition NAM allows treatment of man-made interventions in the hydrological cycle such as groundwater pumping.

Based on the meteorological input data NAM produces catchment runoff as well as information about other elements of the land phase of the hydro-logical cycle, such as the temporal variation of the evapotranspiration, soil moisture content, groundwater recharge, and groundwater levels. The resulting catchment runoff is split conceptually into overland flow, inter-flow and baseflow components.

215


19.4 Basic modelling components

Surface storageMoisture intercepted on the vegetation as well as water trapped in depres-sions and in the uppermost, cultivated part of the ground is represented as surface storage. Umax denotes the upper limit of the amount of water in the surface storage.

The amount of water, U, in the surface storage is continuously diminished by evaporative consumption as well as by horizontal leakage (interflow). When there is maximum surface storage, some of the excess water, PN, will enter the streams as overland flow, whereas the remainder is diverted as infiltration into the lower zone and groundwater storage.

Lower zone or root zone storageThe soil moisture in the root zone, a soil layer below the surface from which the vegetation can draw water for transpiration, is represented as lower zone storage. Lmax denotes the upper limit of the amount of water in this storage.

Moisture in the lower zone storage is subject to consumptive loss from transpiration. The moisture content controls the amount of water that enters the groundwater storage as recharge and the interflow and overland flow components.

EvapotranspirationEvapotranspiration demands are first met at the potential rate from the sur-face storage. If the moisture content U in the surface storage is less than these requirements (U < Ep), the remaining fraction is assumed to be with-drawn by root activity from the lower zone storage at an actual rate Ea. Ea is proportional to the potential evapotranspiration and varies linearly with the relative soil moisture content, L/Lmax, of the lower zone storage

(19.1)

Overland flowWhen the surface storage spills, i.e. when U > Umax, the excess water PN gives rise to overland flow as well as to infiltration. QOF denotes the part of PN that contributes to overland flow. It is assumed to be proportional to

Ea Ep U–( ) LLmax-----------=

216 MIKE BASIN

Basic modelling components

PN and to vary linearly with the relative soil moisture content, L/Lmax, of the lower zone storage

(19.2)

where

CQOFis the overland flow runoff coefficient (0 ≤ CQOF ≤ 1)

TOF is the threshold value for overland flow (0 ≤ TOF ≤ 1).

The proportion of the excess water PN that does not run off as overland flow infiltrates into the lower zone storage. A portion, ∆L, of the water available for infiltration, (PN -QOF), is assumed to increase the moisture content L in the lower zone storage. The remaining amount of infiltrating moisture, G, is assumed to percolate deeper and recharge the groundwater storage.

InterflowThe interflow contribution, QIF, is assumed to be proportional to U and to vary linearly with the relative moisture content of the lower zone storage.

(19.3)

where CKIF is the time constant for interflow, and TIF is the root zone threshold value for interflow (0 ≤ TIF ≤ 1).

Interflow and overland flow routingThe interflow is routed through two linear reservoirs in series with the same time constant CK12. The overland flow routing is also based on the linear reservoir concept but with a variable time constant

(19.4)

QOF CQOFL Lmax TOF–⁄

1 TOF–------------------------------------PN for L Lmax TOF>⁄

0 for L Lmax TOF≤⁄

=

QIF CKIF( ) 1– L Lmax TIF–⁄1 TIF–

----------------------------------U for L Lmax TIF>⁄

0 for L Lmax TIF≤⁄

=

CKCK12 for OF OFmin<

CK12OF

OFmin--------------- β–

for OF OFmin≥

=

217


where OF is the overland flow (mm/hour), OFmin is the upper limit for lin-ear routing (= 0.4 mm/hour), and β = 0.4.

The constant β = 0.4 corresponds to using the Manning formula for mod-elling the overland flow. Equation (19.4) ensures in practice that the rout-ing of real surface flow is kinematic, while subsurface flow being interpreted by NAM as overland flow (in catchments with no real surface flow component) is routed as a linear reservoir.

Groundwater rechargeThe amount of infiltrating water G recharging the groundwater storage depends on the soil moisture content in the root zone

(19.5)

where

TG is the root zone threshold value for groundwater recharge (0 ≤ TG ≤ 1).

Soil moisture contentThe lower zone storage represents the water content within the root zone. After apportioning the net rainfall between overland flow and infiltration to groundwater, the remainder of the net rainfall increases the moisture content L within the lower zone storage by the amount ∆L

(19.6)

BaseflowThe baseflow BF from the groundwater storage is calculated as the out-flow from a linear reservoir with time constant CKBF.

19.5 Extended groundwater components

Drainage to or from neighbouring catchmentsLocal geological conditions may cause part of the infiltrating water to drain to neighbouring catchments. In NAM this loss of water can be described by specifying the ratio of the groundwater catchment area to the topographical catchment area, Carea, with a value less than one. In this

G PN Q– OF( )L Lmax TG–⁄

1 TG–-------------------------------- for L Lmax TG>⁄

0 for L Lmax TG≤⁄

=

∆L PN QOF– G–=

218 MIKE BASIN

Extended groundwater components

case the proportion (1-Carea) of the recharge G is drained to neighbouring catchments. Similarly, water may be drained from neighbouring catch-ments, implying an increased groundwater recharge in the catchment (Carea > 1).

Lower groundwater storageFor a better description of the baseflow, an additional (lower) groundwater storage can be defined. In this case the upper groundwater storage pro-vides the fast responding component of the baseflow, whereas the lower storage usually has a slower response. The recharge to the lower storage is given as a proportion CQLOW of the total recharge G. The routing from the lower storage is described by a linear reservoir with time constant CKLOW.

Shallow groundwater reservoir descriptionThe groundwater level is calculated from a continuity consideration accounting for recharge G, capillary flux CAFLUX, net groundwater abstraction GWPUMP, and baseflow BF. The inclusion of capillary flux and groundwater pumping are optional. The groundwater storage can be treated in two different ways, either as a simple linear reservoir as described in Section Baseflow (p. 218) or as a shallow groundwater reser-voir.

The shallow groundwater reservoir description is appropriate for lowland catchments with little topographical variation and the potential for water logging. The baseflow is given by

(19.7)

where SY is the specific yield of the reservoir, GWL is the groundwater table depth, and GWLBF0 is the maximum groundwater table depth, which causes baseflow.

The parameter GWLBF0 can be interpreted as the distance between the average ground level of the catchment to the water level of the river. Due to the variation in the river water level throughout the year GWLBF0 can be given a significant annual variation.

Capillary fluxThe capillary flux CAFLUX of water from the groundwater to the lower zone storage is assumed to depend on the depth of the groundwater table

BF GWLBF0 GWL–( )SY CKBF( ) 1– for GWL GWLBF0≤

0 for GWL GWLBF0>

=

219


below the ground surface, GWL, as well as on the relative moisture con-tent, L/Lmax, of the lower zone storage

(19.8)

where GWLFL1 is the groundwater table depth at which the capillary flux is 1 mm/day when the lower zone storage is completely dry. Equation (19.8) provides a good fit to the theoretical relationship between the capil-lary flux, the depth to the water table and the soil moisture content pro

19.6 Snow module

Snow accumulation and melt are important hydrological processes in river basins where the snow pack acts as a storage in which precipitation is retained during the cold season and subsequently released as melt water during the warmer parts of the year.

The snow melt component of the runoff is incorporated as an integrated module within NAM. This component is optional and temperature data is only required if the snow routine is selected. Normally the precipitation enters directly into the surface storage. However, during cold periods pre-cipitation is retained in the snow storage from which it is melted in warmer periods. Two different models can be applied; a simple lumped calculation or a more general approach that divides the catchment into a number of altitude zones with separate snow melt parameters, temperature and precipitation input for each zone.

Accumulation and melting of snowSeveral investigations (e.g. /17/) have shown that the shift between precip-itation in the form of rain and snow usually takes place when the air tem-perature is within a narrow interval close to 0o C. In the snow module it is assumed that the precipitation falls as rain when the air temperature is above a certain base temperature level, T0, which can be specified by the user.

The snowmelt QS is calculated using a degree-day approach

(19.9)

CAFLUX 1 L Lmax⁄– GWLGWLFL1--------------------- α–

(mm/day)

α 1,5 0,45GWLFL1+

=

=

QS Csnow T T0–( ) for T T0>

0 for T T0≤

=

220 MIKE BASIN

Snow module

where Csnow is the degree-day coefficient. The generated melt water is retained in the snow storage as liquid water until the total amount of liquid water exceeds the water retention capacity of the snow storage. The excess melt water PS is routed to the NAM model where it contributes to the sur-face storage. The excess melt water contribution PS to NAM is

(19.10)

where WR is the water retention in the snow storage, Cwr is the water retention coefficient, and Ssnow is the snow storage. The new snow storage is calculated by subtracting the excess melt water PS from the snow stor-age.

The rain fraction is added as liquid water and is retained in the snow stor-age if the total liquid water content of the snow pack is below its water retaining capacity. When the air temperature is below T0, the liquid water content in the snow storage freezes with rate Csnow. Evaporation from the snow pack is neglected.

19.6.1 Altitude-distributed snowmelt modelIn mountainous areas temperature, precipitation and snow cover often vary significantly within a single catchment. The runoff simulation for such areas can be improved by dividing the catchment into smaller zones and maintain individual snow storage calculations in each zone.

The altitude-distributed snow model calculates melt water in a number of altitude zones using the degree-day approach. Since in many cases the hydro-meteorological information from mountain basins is quite sparse, the module also includes facilities for distribution of the meteorological information with altitude.

Structure of the altitude-distributed snowmelt moduleThe snow melt module allows the user to define a number of altitude zones within a NAM catchment and adjust the snow melt parameters and the temperature and precipitation input to the model for each zone. The snow melt module maintains individual snow storages and calculates accumulation and melting of snow for each altitude zone. The simulated melt water from all zones is subsequently superposed and routed through the NAM model as illustrated in Figure 19.2. This implies that the same model parameters for infiltration, runoff and groundwater routing are applied for all altitude zones. Such an approach will be appropriate for the large majority of mountain catchments.

PSQmelt for WR CwrSsnow≥

0 for WR CwrSsnow<

=

221


Figure 19.2 Structure of the NAM model with extended snow module.

In special cases where differentiation is needed also in the other parame-ters the catchment in question can be divided into two or more sub-catch-ments. The total simulated discharge is then found by accumulating the simulated discharge from the different sub-catchments using the combined catchment approach in the MIKE 11 RR editor.

In the altitude-distributed snow model, snow melting only takes place from the snow-covered part of each zone. When the water equivalent of the snow pack falls under a user-specified value (minimum storage for full coverage), the area coverage will be reduced linearly with the snow stor-age in the zone.

Snow will not necessarily melt on the location where it falls. Due to wind transport the snow accumulation at wind exposed sites may often be sig-nificantly smaller than at locations well sheltered against wind. Wind exposed conditions are often present at higher altitudes where vegetation is sparse and wind velocities generally high. Furthermore, for the higher parts of mountain ranges, steep slopes having a limited snow storage capacity will often dominate. Snow storage in excess of this capacity will

222 MIKE BASIN

Snow module

at such locations generate avalanches which transport the snow to lower altitudes. Hence, some of the snow falling on wind exposed and/or steep highlands may not melt on the location but be deposited and melting at lower altitudes. To account for such re-distribution of snow and avoid unrealistic accumulation of snow in the cold upper zones a user specified upper limit of the snow storage in the individual zones has been intro-duced in the model. Snow storage exceeding this value will be transferred to the neighbouring lower zone.

19.6.2 Adjustment of temperature and precipitation to altitude zonesThe altitude-distributed snow model operates with three meteorological reference time series; precipitation, temperature and potential evapotran-spiration. In order to account for the large variations in precipitation and temperature with altitude the reference series can be adjusted for each alti-tude zone in two different ways:

lapse rate corrections

individual correction factors applied for each zone

Lapse rate correctionsThe lapse rate correction approach is a very simple but powerful way of adjustment in which the temperature and the precipitation are assumed to vary linearly with the altitude. The only input data required are the aver-age altitude of the various zones, a reference altitude of the time series, and the lapse rates. The temperature lapse rates, however, are known to be quite variable, ranging from high values under dry conditions to lower val-ues under wet conditions. Hence, in the model it is possible to specify two different temperature lapse rates to be used during dry and wet weather conditions, respectively. The model applies the “wet” lapse rate during days with precipitation and the “dry” lapse rate during the rest of the time.

The temperature in each zone is adjusted by the following formula:

(19.11)

where

Tzone temperature in the considered zone

Tref temperature at the reference temperature station

Hzone average height in the zone

TzoneTref Hzone Href–( )βdry+ for P = 0Tref Hzone Href–( )βwet+ for P > 0

=

223


Href height at the reference temperature station

bdry temperature lapse rate for dry conditions

bwet temperature lapse rate for wet conditions

The precipitation in each altitude zone is calculated from the precipitation at the reference station:

(19.12)

where

Pref precipitation at the reference precipitation station

Href height at the reference precipitation series

α precipitation lapse rate

Individual correction factors applied for each zoneIn this case corrections have to be specified by the user for each altitude zone. This method requires more input but also offers a larger flexibility. The corrected meteorological series are calculated using the formulae:

(19.13)

(19.14)

where Tcor,zone,wet and Pcor,zone,dry are the actual temperature corrections for wet and dry conditions, respectively, and Pcor,zone is the relative precipita-tion correction.

If it is not possible to represent the meteorological conditions in the catch-ment by adjustment of one series only, the catchment may be divided into smaller sub-catchments in which one series will be representative. The discharges for the individual sub-catchments are then superposed using the combined catchment approach in the MIKE 11 RR editor.

Pzone Pref 1 Hzone Href–( )α+( )=

TzoneTref Tcor zone dry,,+ for P = 0Tref Tcor zone wet,,+ for P > 0

=

Pzone Pref 1 Pcor zone,+( )=

224 MIKE BASIN

Model parameters

19.6.3 Extended components

Seasonal variation of degree-day coefficientThe simple degree-day approach for calculating snow melt cf. (19.9) can be extended by using a seasonal variation of the degree-day coefficient Csnow. This variation reflects in a conceptual way the seasonal variation of the incoming short wave radiation and the variation in the albedo of the snow surface during the snow season. The albedo is very high (about 0.8) for new, cold snow falling in the beginning of the accumulation season and then decreases with the age of the snow (to a minimum value of about 0.3 in the end of the season).

RadiationThe melting effects caused by the absorbed short wave radiation can be explicitly modelled. In this case an additional snow melting is calculated as

(19.15)

where Crad is the radiation coefficient, and R is the incoming short wave radiation. The total amount of snow melt is calculated as the sum of the snow melt rates given by (19.9), (19.15), and (19.16) (optional), respec-tively.

Condensation of humid air and heat contribution from rainfallThe melting effects from condensation of humid air on the snow surface and the advective heat transferred to the snow pack by precipitation can be explicitly modelled. The effects are calculated as an additional snowmelt

(19.16)

where Crain is a degree-day coefficient, and P is the rainfall. The total amount of snow melt is calculated as the sum of the snow melt rates given by (19.9), (19.15) (optional), and (19.16), respectively.

19.7 Model parameters

This section provides a short description of the model parameters, their physical interpretation and importance along with suggestions for parame-ter adjustments in the calibration.

∆QS CradR=

∆QS CrainP T T0–( )=

225


19.7.1 Surface and root zone parameters

Maximum water content in surface storage Umax

Umax [mm] defines the maximum water content in the surface storage. This storage is interpreted as including the water content in the intercep-tion storage (on vegetation), in surface depression storages, and in the uppermost few cm's of the ground. Typical values of Umax are in the range 10-20 mm.

One important characteristic of the model is that the surface storage must be at its maximum capacity, i.e. U ≥ Umax before any excess water, PN, occurs. In dry periods, the amount of net rainfall that must occur before any overland flow occurs can be used to estimate Umax.

Maximum water content in root zone storage Lmax

Lmax [mm] defines the maximum water content in the lower or root zone storage. Lmax can be interpreted as the maximum soil moisture content in the root zone available for the vegetative transpiration. Ideally, Lmax can then be estimated by multiplying the difference between field capacity and wilting point of the actual soil with the effective root depth. The difference between field capacity and wilting point is referred to as the available water holding capacity (AWHC). For estimation of AWHC, moisture con-tents for different soil types at pF-value 2.5, corresponding approximately to field capacity, and pF-value 4.2, corresponding to wilting point are shown in Table 19.1

It should be noted that Lmax represents the average value for an entire catchment, i.e. an average value for the various soil types and root depths of the individual vegetation types. Hence, Lmax cannot in practice be esti-mated from field data, but an expected interval can be defined.

Since the actual evapotranspiration is highly dependent on the water con-tent of the surface and root zone storages, Umax and Lmax are the primary parameters to be changed in order to adjust the water balance in the simu-lations. In the preliminary stages of the model calibration, it is recom-mended to fix the relation between Umax and Lmax, leaving only one storage parameter to be estimated. As a rule, Umax = 0.1Lmax can be used unless special catchment characteristics or hydrograph behaviour indicate otherwise.

Table 19.1 Moisture content in cm3/cm3 at (effective) saturation (θs) and at pF-values of 2.5(θ2.5) and 4.2(θ4.2), for eleven textural classes and from three sources: (1) Rawls et al. (1982),/13/; (2) Cosby et al.

226 MIKE BASIN

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(1984),/5/; (3) Rijtema (1969), /16/.

Overland flow runoff coefficient CQOFCQOF is a very important parameter, determining the extent to which excess rainfall runs off as overland flow and the magnitude of infiltration.

CQOF is dimensionless with values between 0 and 1. Physically, in a lumped manner, it reflects the infiltration and also to some extent the recharge conditions. Small values of CQOF are expected for a flat catch-ment having coarse, sandy soils and a large unsaturated zone, whereas large CQOF-values are expected for catchments having low, permeable soils such as clay or bare rocks. CQOF-values in the range 0.01-0.90 have been experienced.

It should be noted that during periods where the groundwater table is at the ground surface the model excludes the infiltration component, and hence CQOF becomes redundant.

Time constant for interflow CKIFCKIF [hours] determines together with Umax the amount of interflow ((CKIF)-1 is the quantity of the surface water content U that is drained to interflow every hour). It is the dominant routing parameter of the interflow because CKIF >> CK12.

Physical interpretation of the interflow is difficult. Since interflow is sel-dom the dominant streamflow component, CKIF is not, in general, a very important parameter. Usually, CKIF-values are in the range 500-1000 hours.

Time constant for routing interflow and overland flow CK12

The time constant for routing interflow and overland flow CK12 [hours] determines the shape of hydrograph peaks. The value of CK12 depends on the size of the catchment and how fast it responds to rainfall. Typical val-ues are in the range 3-48 hours.

227


The time constant can be inferred from calibration on peak events. If the simulated peak discharges are too low or arriving too late, decreasing CK12 may correct this, and vice versa.

Root zone threshold value for overland flow TOFTOF is a threshold value for overland flow in the sense that no overland flow is generated if the relative moisture content of the lower zone stor-age, L/Lmax, is less than TOF. The behaviour of the threshold value is illus-trated in Figure 19.3. Similarly, the root zone threshold value for interflow TIF and recharge TG act as threshold values for generation of interflow and recharge, respectively.

Figure 19.3 Generation of overland flow.

Physically, the three threshold values should reflect the degree of spatial variability in the catchment characteristics, so that a small homogeneous catchment is expected to have larger threshold values than a large hetero-geneous catchment.

For catchments with alternating dry and wet periods, the threshold values determine the onset of the flow components in the periods where the root zone is being filled up. This can be used in model calibration. It should be noted that the threshold values have no importance in wet periods. The significance of the threshold value varies from catchment to catchment and is usually larger in semi-arid regions.

In areas with alternating dry and wet seasons, TOF can be estimated on the basis of situations where even very heavy rainfall does not give rise to the quick response of the overland flow component. The parameter has an impact only during the first, few weeks of the wet season. Values of TOF in the range 0-0.7 have been experienced.

228 MIKE BASIN

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Root zone threshold value for interflow TIFThe root zone threshold value for interflow has the same function for interflow as TOF has for the overland flow. It is usually not a very impor-tant parameter, and it can in most cases be given a value equal to zero.

19.7.2 Groundwater parameters

Baseflow time constant CKBF

The time constant for baseflow, CKBF [hours], determines the shape of the simulated hydrograph in dry periods. According to the linear reservoir description the discharge in such periods is given by an exponential decay. CKBF can be estimated from hydrograph recession analysis. CKBF-values in the range 500-5000 hours have been experienced.

If the recession analysis indicates that the shape of the hydrograph changes to a slower recession after a certain time, an additional (lower) groundwater storage can be added to improve the description of the base-flow.

Root zone threshold value for groundwater recharge TGThe root zone threshold value for recharge has the same effect on recharge as TOF has on the overland flow. It is an important parameter for simulat-ing the rise of the groundwater table in the beginning of a wet season.

Recharge to lower groundwater storage CQLOW

In some cases the shape of the hydrograph recession changes to a slower recession after a certain period. To simulate this, a lower groundwater storage may be included. The parameter CQLOW determines the proportion of the recharge that percolates to the lower groundwater storage. CQLOW together with CKlow can be estimated from hydrograph recession analysis.

Time constant for routing lower baseflow CKlow

The baseflow from the lower groundwater storage is modelled using a lin-ear reservoir with time constant CKlow [hours]. The time constant can be estimated from hydrograph recession analysis. Usually, CKlow is larger than CKBF.

Ratio of groundwater catchment to topographical catchment area Carea

Drainage to or from neighbouring catchments can be modelled by specify-ing a value of Carea different from 1. Carea specifies the amount of recharge G that is being drained. If Carea < 1, part of the recharge, (1-Carea)G, is drained to another catchment, whereas for Carea > 1, the amount (Carea-1)G is added to the catchment recharge.

229


Maximum groundwater depth causing baseflow GWLBF0

The maximum depth to the groundwater table for which baseflow occurs, GWLBF0 [m], represents the outflow level of the groundwater reservoir given as the distance between the average ground level of the catchment and the minimum level of the river to which it drains. In low, flat areas the annual variation of this distance may be of importance and the facility to allow GWLBF0 to vary seasonally is provided in NAM.

GWLBF0 and the specific yield SY can be calibrated by comparing the sim-ulated groundwater level with observations.

Specific yield SY

Values of the specific yield for the groundwater storage may often be assessed from hydrological data e.g. pump tests. Alternatively, SY-values can be estimated from the literature for different soil types. Small values are found for clay (0.01-0.1) and high values for sand (0.1-0.3).

Groundwater depth for unit capillary flux GWLFL1

GWLFL1 [m] is the depth to the groundwater table which yields an upward capillary flux of 1 mm/day when the moisture content of the upper soil layers is at wilting point, i.e. L = 0. This parameter will depend on the soil type, and values for 20 soil types according to Rijtema (1969), /16/ are listed in Table 19.2.

Table 19.2 Depth to the groundwater table corresponding to a capillary flux of 1 mm/day for 20 soil types.

Soil Type GWLFL1 [m]

1. Coarse sand 0.5

2. Medium coarse sand 0.6

3. Medium fine sand 0.9

4. Fine sand 1.5

5. Humus loamy medium coarse sand 1.2

6. Light loamy medium coarse sand 0.7

7. Loamy medium coarse sand 0.5

8. Loamy fine sand 1.7

9. Sandy loam 0.7

10. Loess loam 1.5

230 MIKE BASIN

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19.7.3 Snow module parameters

Degree-day coefficient Csnow

The snow melts at a rate defined by the degree-day coefficient Csnow [mm /°C/day]. A seasonal variation of Csnow can be defined in order to account for the seasonal variations of the incoming short wave radiation and the albedo of the snow surface. Typical values of Csnow are in the range 2-4 mm/°C/day.

Base temperature (snow/rain) T0

The precipitation is assumed to fall as snow if the temperature is below the base temperature T0 [°C]. For temperatures above T0 the snow in the snow storage is melting. The base temperature is usually close to zero degrees Celsius.

Radiation coefficient Crad

The radiation coefficient Crad [m2/W/mm/day] determines the rate of snow melting caused by the absorbed short wave radiation.

Rainfall degree-day coefficient Crain

The rainfall degree-day coefficient Crain [mm/mm/°C/day] determines the rate of snow melting caused by condensation of humid air on the snow

11. Fine sandy loam 2.5

12. Silty loam 2.8

13. Loam 1.9

14. Sandy clay loam 2.2

15. Silty Clay Loam 1.8

16. Clayey Loam 1.0

17. Light clay 2.9

18. Basin clay 0.4

19. Silty clay 1.4

20. Peat 0.6

Table 19.2 Depth to the groundwater table corresponding to a capillary flux of 1 mm/day for 20 soil types.

Soil Type GWLFL1 [m]

231


surface and the advective heat transferred to the snow pack by precipita-tion.

19.8 Initial conditions

The initial conditions required by the NAM model consist of the initial water contents in the surface and root zone storages, together with initial values of overland flow, interflow, and baseflow.

If a lower groundwater reservoir is specified, the initial baseflow from both the upper and the lower reservoir should be specified. If the snow module is included, the initial value of the snow storage should be speci-fied.

If a simulation commences at the end of a dry period, it is often sufficient to set all initial values to zero, except the water content in the root zone and the baseflow. The water content in the root zone should be about 10-30% of the capacity and the baseflow should be given a value close to the observed discharge.

Improved estimates of the initial conditions may be obtained from a previ-ous simulation, covering several years, by noting the appropriate moisture contents of the root zone and baseflow at the same time of the year as the new simulation will start.

In general it is recommended to disregard the first 3-6 months of the NAM simulation in order to eliminate the influence of erroneous initial condi-tions.

19.9 Model calibration

In the NAM model the parameters and variables represent average values for the entire catchment. While in some cases a range of likely parameter values can be estimated, it is not possible, in general, to determine the val-ues of the NAM parameters on the basis of the physiographic, climatic and soil physical characteristics of the catchment, since most of the parameters are of an empirical and conceptual nature. Thus, the final parameter esti-mation must be performed by calibration against time series of hydrologi-cal observations.

19.9.1 Calibration objectives and evaluation measuresThe following objectives are usually considered in the model calibration

232 MIKE BASIN

Model calibration

1 A good agreement between the average simulated and observed catch-ment runoff (i.e. a good water balance)

2 A good overall agreement of the shape of the hydrograph

3 A good agreement of the peak flows with respect to timing, rate and volume

4 A good agreement for low flows

In this respect it is important to note that, in general, trade-offs exist between the different objectives. For instance, one may find a set of parameters that provide a very good simulation of peak flows but a poor simulation of low flows, and vice versa.

In the calibration process, the different calibration objectives 1-4 should be taken into account. If the objectives are of equal importance, one should seek to balance all the objectives, whereas in the case of priority to a certain objective this objective should be favoured.

For a general evaluation of the calibrated model, the simulated runoff is compared with discharge measurements. For individual calibration of the groundwater parameters, the simulated average groundwater level can be compared with groundwater level measurements in the catchments.

Both graphical and numerical performance measures should be applied in the calibration process. The graphical evaluation includes comparison of the simulated and observed hydrograph, and comparison of the simulated and observed accumulated runoff. The numerical performance measures include the overall water balance error (i.e. the difference between the average simulated and observed runoff), and a measure of the overall shape of the hydrograph based on the coefficient of determination or Nash-Sutcliffe coefficient (/11/)

(19.17)

where Qsim,i is the simulated discharge at time i, Qobs,i is the corresponding observed discharge, and is the average observed discharge. A perfect match corresponds to R2 = 1.

R2 1

Qobs i, Qsim i,–[ ]2

i 1=

N

∑

Qobs i, Qobs–[ ]2

i 1=

N

∑

--------------------------------------------------–=

Qobs

233


An exact agreement between simulations and observations must, however, not be expected. The goodness-of-fit of the calibrated model is affected by different error sources, including

1 Errors in meteorological input data

2 Errors in recorded observations

3 Errors and simplifications inherent in the model structure

4 Errors due to the use of non-optimal parameter values

In model calibration only error source (4) should be minimised. In this respect it is important to distinguish between the different error sources since calibration of model parameters may compensate for errors in data and model structure. For catchments with a low quantity or quality of data, less accurate calibration results may have to be accepted.

Satisfactory calibrations over a full range of flows usually require continu-ous observations of runoff for a period of 3-5 years. Runoff series of a shorter duration, however, will also be useful for calibration, although they do not ensure an efficient calibration of the model. For a proper eval-uation of the reliability and hydrological soundness of the calibrated model it is recommended to validate the model on data not used for model calibration (split-sample test). Some general aspects related to calibration and validation of hydrological models are described in Refsgaard and Storm (1996), /15/.

19.9.2 Manual calibrationThe process of model calibration is normally done either manually or by using computer-based automatic procedures. In this section a manual cali-bration strategy for the NAM model is outlined. Application of an auto-matic optimisation routine for calibration of the basic NAM model is described in the subsequent section.

In manual calibration, a trial-and-error parameter adjustment is made until satisfactory results are obtained. It is recommended, especially for the less experienced users, to change only one parameter between each trial, so that the effect of the change can be easily discerned. The manual calibra-tion strategy outlined below is based on the different rainfall-runoff proc-ess descriptions for calibration of the relevant model parameters, i.e. the parameters that mostly affect the considered process description (see also Section 19.7 Model parameters (p. 225)).

A calibration usually commences by adjusting the water balance in the system. The total evapotranspiration over a certain period should corre-spond to the accumulated net precipitation minus runoff. The evapotran-

234 MIKE BASIN

References

spiration will increase when increasing the maximum water contents in the surface storage Umax and the root zone storage Lmax, and vice versa.

The peak runoff events are caused by large quantities of overland flow. The peak volume can be adjusted by changing the overland flow runoff coefficient (CQOF), whereas the shape of the peak depends on the time constant used in the runoff routing (CK12).

The amount of base flow is affected by the other runoff components; a decrease in overland flow or interflow will result in a higher baseflow, and vice versa. The shape of the baseflow recession is a function of the base-flow time constant (CKBF). If the baseflow recession changes to a slower recession after a certain time, a lower groundwater reservoir should be added, including calibration of CQlow and CKlow.

Initially, the root zone threshold values TOF, TIF and TG can be set to zero. After a first round of calibration of the parameters Umax, Lmax, CQOF, CK12 and CKBF, the threshold parameters can be adjusted for fur-ther refinement of the simulation results.

For individual calibration of the groundwater parameters GWLBF0 and SY, the simulated groundwater level is compared to observed groundwater levels. Inclusion of the shallow groundwater reservoir description is important in lowland areas, as found e.g. in swamps or river delta areas, where the groundwater table may reach the ground surface during the wet season.

The snow module parameters are calibrated against periods with snow-melt runoff.

19.10 References

/2/ Abbott, M.B. and J.C. Refsgaard (eds) (1996), Distributed Hydro-logical Modelling, Kluwer Academic Press, The Netherlands, 321 p.

/3/ Brakensiek, D.L. (1979), Comments on 'Empirical Equations for some soil Hydraulic Properties' by Roger B. Clapp and George M. Hornberger, Water Resources Research, 15 (4), 989-990.

/4/ Brakensiek, D.L., Engleman, R.L. and Rawls, W.J. (1981), Varia-tion within texture classes of soil water parameters, Trans. ASAE,

235


24, 335-339.

/5/ Cosby, B.J., Hornberger, G.M., Clapp, R.B. and Ginn, T.R. (1984), A statistical exploration of the relationships of soil moisture charac-teristics to the physical properties of soils, Water Resources Research, 20 (6), 682-690.

/6/ Doorenbos, J. and W.O. Pruitt (1977), Guidelines for Predicting Crop Water Requirements. FAO Irrigation and Drainage paper No. 24. Food and Agricultural Organization of the United Nations.

/7/ Duan, Q., Sorooshian, S., Gupta, V. (1992), Effective and efficient global optimization for conceptual rainfall-runoff models, Water Resources Research, 28(4), 1015-1031.

/8/ Li, R.-M., Stevens, M.A. and Simons, D.B. (1976), Solutions to Green-Ampt infiltration equations, J. Irrig. and Drain. Div., Amer. Soc. Civil. Eng., 102 (IR2), 239-248.

/9/ Madsen, H. (1999), Automatic calibration of a conceptual rainfall-runoff model using multiple objectives, Journal of Hydrology, Sub-mitted.

/10/ McCuen, R.H., Rawls, W.J. and Brakensiek, D.L. (1981), Statistical analysis of the Brooks-Corey and Green-Ampt parameters across soil textures, Water Resources Research, 17, 1005-1013.

/11/ Nash, I.E. and Sutcliffe, I.V. (1970), River flow forecasting through conceptual models, Part I, Journal of Hydrology, 10, 282-290.

/12/ Nielsen, S.A. and E. Hansen (1973), Numerical simulation of the rainfall runoff process on a daily basis, Nordic Hydrology, 4, 171-190.

/13/ Rawls, W.J., Brakensiek, D.L. and Saxton, K.E. (1982), Estimation of soil water properties, Transactions of the ASAE, 25, 1316-1320.

/14/ Refsgaard, J.C. and J. Knudsen (1997), Operational validation and intercomparison of different types of hydrological models. Water Resources Research, 32(7), 2189-2202.

/15/ Refsgaard, J.C. and Storm, B. (1996), Construction, calibration and validation of hydrological models, In: Distributed Hydrological modelling (eds. M.B. Abbott and J.C. Refsgaard), Kluwer Aca-

236 MIKE BASIN

References

demic Press, The Netherlands, 41-54.

/16/ Rijtema, P.E. (1969), Soil moisture forecasting, Nota 513, Instituut voor Cultuurtechniek en Waterhuishouding, Wageningen, The Netherlands.

/17/ U.S. Army Corps of Engineers (1956), Snow hydrology: Summary report on snow investigations.

237


238 MIKE BASIN

I N T E R F A C E P R O G R A M M I N G G U I D E

239

240 MIKE BASIN

Overview of interfaces and enumerations

20 FOR VISUAL BASIC MACRO PROGRAMMING

20.1 Overview of interfaces and enumerations

There are two interfaces, or objects, that the MIKE BASIN engine pro-vides, namely

1 DHI_MikeBasin_Engine.Engine

2 DHI_MikeBasin_Engine.ModelObject.

The Engine is the core object that contains the entire model setup and sim-ulation information. The model setup itself is composed of ModelObjects.

ModelObjects can be physical features or network elements, such as nodes, reaches, and catchments. Additional types of ModelObjects are logical or computational entities, such as allocation rules and water quality models.

Note the difference in architecture to what you may be used to from work-ing just with the ArcGIS user interface. In ArcGIS, you have features, and each feature (or network element) has a property dialog. In these dialogs, also rules and water quality parameter sets (models) applicable for the fea-ture can be defined. Under the hood, however, rules and water quality models are separate entities. Relationships define the link between fea-tures and logical entities. The ModelObject interface also provides meth-ods to return the rules applicable for a feature-type ModelObject.

Both MIKE BASIN interfaces contain methods that refer to some enumer-ations that are defined in the DHI Mike Basin Data Access Component (DHI.MikeBasin.Data.tlb).

20.2 Some tips and tricks

The following is mostly intended for those not so familiar with Visual Basic. There is full help available for Visual Basic from its Editor, but most users will find they can get started with MIKE BASIN programming with just a little bit of assistance and a few tips and tricks.

20.2.1 Call by reference Several methods use arguments passed "by reference" ("out" in C#). These are methods that have, loosely speaking, more than one return value. Technically, a method can only have one return value, though. In Visual

Interface Programming Guide 241

For Visual Basic macro programming

Basic, arguments passed by reference have to be declared in their proper type. An example for a call by reference is

Dim CurrTimeStep As Date

Dim CurrTimeStepLength As Double

engine.GetCurrTimeStepInfo CurrTimeStep, CurrTimeStepLength

Assuming "engine" is a DHI_MikeBasin_Engine.Engine variable, this call "fills in" the requested values into the two arguments. Arguments passed by reference are denoted ByRef in the documentation below. Accordingly, the syntax used to document the method in the example is

GetCurrTimeStepInfo ByRef Date CurrTimeStep, ByRef Double Curr-TimeStepLength

20.2.2 Call by value Most commonly, arguments are passed to a method only "for informa-tion", not to be "filled in" by the method. Visual Basic, however, by default passes arguments by reference. Therefore, arguments not marked ByRef, explicity ensures that your arguments are not going to be changed in the method. An example of a call by value is

Dim CurrTimeStep

CurrTimeStep = #12/15/1981#

engine.SimulateTimeStep CurrTimeStep

Again assuming "engine" is an DHI_MikeBasin_Engine.Engine variable, CurrTimeStep will still be December 15, 1981 after the call to Simulate-TimeStep. Accordingly, the syntax used to document the method in the example is

SimulateTimeStep Date SomeDate

20.2.3 PropertiesProperties are "shorthand" methods with one argument or return value, respectively. A property can be set, get (read-only), or both. An example for properties is

engine.Silent = True ' set property

Dim bSilent As Boolean

242 MIKE BASIN

Some tips and tricks

bSilent = engine.Silent ' get property

The syntax used to document the property in the example is

Boolean Silent [get; set]

20.2.4 Option ExplicitIn Visual Basic by default, variables do not have to be declared at all, so it is legal to write, e.g.,

Dim CurrTimeStep

CurrTimeStep = #12/15/1981#

engine.SimulateTimeStep CurrTimeSteps

This code looks very much like the above example, but note the small spelling mistake in the argument. Such mistakes are actually rather com-mon, and often difficult to find. The above code would execute, but with CurrTimeSteps still having its default value, 0, thus causing an error.

To avoid inadvertent behavior, you should place the single line

Option Explicit

on the very top of your macro. With this option, Visual Basic will not allow non-declared variables, and in the above example, warn you that CurrTimeSteps is not declared.

20.2.5 Static vs dimAlmost always, you will want to declare your variables using the Dim key-word, as in the examples above. Variables declared in this way persist only for the lifetime of the macro, i.e., until the code comes to an Exit Sub or End Sub (or Function) statement. In situations, however, where you want a macro to run many simulations, you can save time by declaring the MIKE BASIN engine as a static variable. Static variables persist as long as the calling application (ArcMap or Excel) is open. A typical example is opti-mization using Solver in Excel, working on a function like

Public Function MikeBasinEval(SomeVariableToBeOptimized)

Static engine As DHI_MikeBasin_Engine.Engine specified



If engine Is Nothing Then ' first-time call only

Set engine = new DHI_MikeBasin_Engine.Engine

engine.Initialize "c:\example", "ProjectData.mdb"

End If

' code to set some inputs for engine

engine.Simulate

' code to retrieve some results from engine

End Function

The first time the above function is called, all variables, also static ones, are uninitialized (0 or "Nothing"). The if statement detects that the MIKE BASIN engine variable is created and the setup is initialized (see details on that method below). Any subsequent time the function is called, engine is no longer nothing, and the time-consuming call to Initialize can be skipped.

20.2.6 Daisy-chaining vs temporary variablesFor many common tasks, you may need to call more than one method. For example, a very common pattern is to have created a DHI_MikeBasin_Engine.Engine variable, then request a ModelObject from it, and finally retrieve a result for that ModelObject. The "daisy-chaining" code for this task is:

result = engine.GetModelObject("N1").GetAverageResult("Net flow to node", #12/15/1981#, #1/1/1982#)

The alternative is to create a temporary variable to hold the result of the first method:

Dim feature As DHI_MikeBasin_Engine.ModelObject

Set feature = engine.GetModelObject("N1")

result = feature.GetAverageResult("Net flow to node", #12/15/1981#, #1/1/1982#)

Daisy-chaining keeps the code shorter, but is more difficult to debug and often also slower. Whenever you want to call multiple methods for the fea-

244 MIKE BASIN

DHI_MIKEBASIN_Engine.Engine interface methods

ture above, it is much faster to only "get" it only once and then store the result for subsequent calls.

20.3 DHI_MIKEBASIN_Engine.Engine interface methods

In the following sections, the most commonly used methods are outlined.

20.3.1 InitializeInitialize String WorkDir, String DatabaseName

This method initializes the MIKE BASIN engine. That is, it establishes the model set-up as created in the user interface. Basically, the principle with using macros for MIKE BASIN is to first create a setup in the regular user interface, run a "base" simulation, and then do any modifications in the macro. Accordingly, this method must be called before any simulation.

The argument WorkDir is the working directory for the simulation, which is the directory that also contains the mxd document. It also contains the MSAccess database indicated by the argument DatabaseName.

20.3.2 SimulateSimulate

Runs the entire simulation for the same time period as specified in the user interface.

20.3.3 OptimizeBoolean Optimize OptimizationModes Mode

This method performs an optimization as defined in the user interface. The Mode argument indicates the desired behavior on iteration errors (ignore, warn, stop). The returned value is true if the optimization converged, pos-sibly at any variables' bound.

20.3.4 RunAllBoolean RunAll String WorkDir, String DatabaseName, Boolean Silent, Boolean RegTest

This is a single method that "does it all". In essence, it is a combination of Initialize and Simulate or Optimize (whichever of the last two is relevant). For details on the first two arguments, see Initialize (p. 245). The argu-ment Silent can be set to true to suppress any dialogs. The argument



RegTest can enable regression tests (not publicly available). The return value is true if the method has finished successfully, false otherwise.

20.3.5 SimulateTimeStepSimulateTimeStep Date SomeDate

This method runs a single time step in the simulation, starting at Some-Date. Stepwise simulation is an alternative to Simulate, giving the possi-bility to control the simulation. For example, one can connect a user to a reservoir and change that user's demand dynamically based on several pre-vious time steps' or the current time step's simulation results for the reser-voir level. Make sure the first call to SimulateTimeStep is with the proper start date/time.

SimulateTimeStep is a very flexible method, because the argument Some-Date does not have to be continuously increasing as in a regular simula-tion. The options are:

Date input in the same sequence as it has in a regular simulation or the Simulate method.

Date repeated (several iterations for the same time step, the iteration loop controlled by the Visual Basic macro).

Date as an earlier time step for which initial conditions were remem-bered ('hotstart', allowing macro-controlled iterations of sub-periods in the simulation. For more information, see RememberForHotstart (p. 246).

20.3.6 AdvanceTimeStepDate AdvanceTimeStep Boolean obsolete

Because the time stepping for SimulateTimeStep can included repeated iterations of the same time step, this method is needed to advance the sim-ulation to the next time step once a user-defined iteration criterion is ful-filled. The argument is obsolete and retained only for backward compatibility. The returned value is the next time step's date, as deter-mined by the sequence in a regular simulation. A value of 0 is returned when the simulation is finished.

20.3.7 RememberForHotstartRememberForHotstart Boolean SaveToFile

This method causes the MIKE BASIN engine to remember all state varia-bles for the current time step T1, such that all initial conditions (e.g., reser-voir levels, groundwater levels, solute masses, volumes in river branches

246 MIKE BASIN

Lesser used DHI_MIKEBASIN_Engine.Engine methods

with routing) are given when the simulation later goes back in time to T1. RememberForHotstart must be called immediately after Advance-TimeStep, before any call to SimulateTimeStep for the new time step (as such a call generally changes the state variables). Set the argument SaveToFile to true to also save the state to a file.

20.3.8 GetModelObjectModelObject GetModelObject Variant UserDefNameOrIDNameOrZeroBa-sedIndex

A MIKE BASIN setup consists for a collection of ModelObjects. That is, the four types of nodes, reaches, catchments, allocation rules, and water quality models. GetModelObject retrieves any such object, as described by either

its user-defined name, as entered in the "Name" field in feature's prop-erty dialog, the Water Quality parameter set dialog, or the "Comment" field of an allocation rule, depending on the type of model object. Note that such name has to be unique for this method to succeed.

The short ID also shown in results time series (e.g., "N15" for the river node with feature ID 15)

A zero-based index within all ModelObjects in the setup.

The ModelObject interface is documented separately.

20.3.9 GetIthRuleForNodeModelObject GetIthRuleForNode ModelObject NodeObject, Long iZero-Based, Boolean bUpstream, Boolean bDownstream

This method returns the i-th rule relevant for NodeObject. That is, a Mod-elObject that is a node, or 0 if the i-th rule does not exist. The returned rule is also a ModelObject. Set bUpstream and bDownstream to true to retrieve only those rules where NodeObject is the upstream and downstream end, respectively, of a rule. To retrieve all rules for a node, call this method in a while loop, incrementing iZeroBased until the return value is 0.

20.4 Lesser used DHI_MIKEBASIN_Engine.Engine methods

The following sections outline other methods available to you, but they are typically less commonly used.



20.4.1 SetSimulationOptionsSetSimulationOptions WqSimulationModes WqMode, Boolean bGroundwa-ter

This method allows you to override the simulation settings otherwise defined in the Options dialog in the user interface. To be effective, this method must be called before Initialize.

The argument WqMode refers to one of three water quality simulation modes from the Options dialog, either No WQ modeling, WQ modeling for all solutes, or WQ modeling for all solutes except DO. The argument bGroundwater refers to the groundwater modeling option in that dialog.

20.4.2 SetSimulationTimingSetSimulationTiming Date SimStart, Date TimeOfForecast, Date SimEnd, Double TimeStepInSeconds, Long StochasticPeriodInYears

With this method, the simulation timing can be changed relative to the val-ues specified in the "Run MIKE BASIN" dialog in the user interface. The most relevant dates that can be edited are simulation start and end. The time step must be given in seconds, or -1.0 to indicate monthly time steps. This method should be called immediately after Initialize, before any call to Simulate or SimulateTimeStep.

All specs relevant to simulation timing are thus collected in a single multi-argument method rather than provided as individual properties to set. This design makes it easier to check the various constraints related to timing. Individual get-only properties for timing specs are provided, however.

The arguments TimeOfForecast and StochasticPeriodInYears refer to options not available from the user interface. StochasticPeriodInYears can be set to 1 in the "Run MIKE BASIN" dialog when checking the "reset states every year" option. However, intervals other than 1 year are also possible. The TimeOfForecast argument is related to MIKE BASIN's abil-ity to perform data assimilation, which is not yet fully documented. Fore-cast can be disabled by setting TimeOfForecast for 1st Jan 100.

20.4.3 SetInputTimeSeriesValueSetInputTimeSeriesValue String UserDefNameOrIDName, String TSFileName, String TSItemName, Date When, Double valueInUserUnits

Changes an input value in a time series associated with a node, reach, or catchment feature as identified by the argument UserDefNameOrIDName, which can be

248 MIKE BASIN


1 the user-defined name, as entered in the "Name" field in feature's prop-erty dialog. Note that such name has to be unique in order for this method to succeed.

2 The short ID also shown in results time series (e.g., "N15" for the river node with feature ID 15)

For this feature, it affects the time series specified by its filename (argu-ment TSFileName), which can be either relative to the WorkingDirectory (recommended for portability of macro code) or absolute. For this time series, it affects the entry for in the column with name equal to the argu-ment TSItemName. In that column, the value at time When is set to valueI-nUserUnits.

SetInputTimeSeriesValue is maintained mostly for backward compatibil-ity with pre-2005 versions of MIKE BASIN macros. Accordingly, this method will also scan the time series for all rules associated with a node if UserDefNameOrIDName referes to a node. Currently, rules are ModelOb-jects in their own right, and can be retrieved using GetModelObject.

SetInputTimeSeriesValue is not as fast as its newer alternatives (see the code generated with the Macro Assistant), but it is a shorthand method that "does it all" in a single line of code. Also, it only applies to time series that are stored as remote files, and not locally in the input database itself.

20.4.4 GetCurrTimeStepInfoGetCurrTimeStepInfo ByRef Date CurrTimeStep, ByRef Double Curr-TimeStepLength

Get information on the current time step, both start time and length (in seconds). This method can be useful when running a simulation time step by time step, i.e., using AdvanceTimeStep. That method returns the next time steps start, but not its length. If you require that latter information, use GetCurrTimeStepInfo.

20.4.5 ShowStatusShowStatus

This method is for reference only. It shows the working directory and database specified in Initialize and whether or not the MIKE BASIN engine is ready to run simulations.

20.4.6 ShowAnyWarningsShowAnyWarnings



Shows the list of warnings for the above simulation (if any). Unlike errors, warnings do not cause exceptions that stop the macro, but contain useful information on inputs that probably are incorrect.

20.4.7 FinishSimulationFinishSimulation Boolean ForceWrite

This method need generally not be called explicitly. It writes out the results time series and makes any feature - time series associations. Gener-ally, FinishSimulation is automatically called after the last Advance-TimeStep, i.e., when a simulation has reached its end time. Only in rare cases where you may want to override the default behavior can this method become useful. Furthermore, setting the argument ForceWrite to true is only relevant when running an optimization, which is an iterative repeat of many calls to Simulate. Only the final one - with the optimal var-iables - should write out results.

20.4.8 GetResultsTSObjectTSObject GetResultsTSObject

All results from a simulation a stored in a (big) in-memory object, which can be retrieved with this method. The returned object is of type TSOb-ject, DHI's TimeSeries COM object. Many methods and interface are defined for TSObject; you can see the full documentation under www.mikeobject.com. This method is mainly for advanced users.

20.4.9 GetTemplateModelObjectModelObject GetTemplateModelObject ObjectTypes objType

Return a "typical" instance of a type of model object. This method is mainly relevant if you want to see the results and inputs relevant for any ModelObject of a particular type. This method can be called before Initial-ize, but after any call to SetSimulationOptions.

20.4.10 PreInitializePreInitialize

Not implemented yet.

20.4.11 Initialize2Initialize2


250 MIKE BASIN


20.4.12 EngineEngine(Boolean bOpenMI)

.Net interface only. Alternative constructor used by the OpenMI wrapper for MIKE BASIN.

20.4.13 FindModelObjectModelObject FindModelObject(ObjectTypes objType, Int32 withinTypeOb-jectID)

.Net interface only.

This method is an alternative to GetModelObject. Get a reference to a Mod-elObject, found by its type and primary key value in its attributes table. Should be called after Initialize.

20.4.14 GetRulesForNodeModelObject [ ] GetRulesForNode(ModelObject NodeObject, Boolean bUp-stream, Boolean bDownstream


This method is an alternative to GetIthRuleForNode. It returns an array of all rules for a node rather than the i-th one. Returning arrays is not possi-ble in the COM interface.

20.4.15 RestoreFromHotstartFileDateTime RestoreFromHotstartFile(DateTime DesiredTime, String Hot-StartSubDirectory, Boolean bExactTime)


Read all states (ie, initial conditions) from hotstart file, as generated by a call to RememberForHotstart with argument True, when the simulation was at DesiredTime. The argument HotStartSubDirectory indicates on optional subdirectory of the WorkingDirectory to search for hotstart files in. Leave this argument empty if you haven't moved hotstart files after a call to RememberForHotstart. If no hotstart file is available for DesiredTime, the argument bExactTime becomes relevant. If it is set to false, the method will try to use the closest hotstart file instead, otherwise it will fail. The return value is the date for which the hotstart file is valid, 0 if none.

After this method, you can can call Simulate() or SimulateTimeStep(). Internally in the MIKE BASIN engine, the current time step is not changed by a call to RestoreFromHotstartFile.



20.5 DHI_MIKEBASIN_Engine.Engine interface properties

20.5.1 InitializedBoolean Initialized [get]

Indicates whether Initialize has finished successfully.

20.5.2 WorkingDirectoryString WorkingDirectory [get; set]

The directory where the results time series is to be saved. Also any optimi-zation log and hotstart files are stored in this directory.

20.5.3 WriteOutputBoolean WriteOutput [set]

Determines whether simulation results should be written to a file.

20.5.4 NumberOfNetworkElementsLong NumberOfNetworkElements [get]

Returns the total number of features (nodes, reaches, and catchments) in a model setup.

20.5.5 NumberOfObjectsLong NumberOfObjects [get]

Returns the total number of ModelObjects in a setup. Besides features and network elements, this number also includes allocation rules and water quality models.

20.5.6 SimulationStartDATE SimulationStart [get]

The start of the simulation as specified in the user interface. See also Set-SimulationTiming (p. 248).

20.5.7 SimulationEndDATE SimulationEnd [get]

The end of the simulation as specified in the user interface. See also Set-SimulationTiming (p. 248).

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20.5.8 TimeOfForecastDATE TimeOfForecast [get]

The time of forecast up to which simulated values can be corrected by observations, and beyond which the error model can estimate corrections. This functionality is not yet accessible from the user interface. See also SetSimulationTiming (p. 248).

20.5.9 TimeStepDouble TimeStep [get]

The simulation time step as specified in the user interface, -1.0 for monthly. See also SetSimulationTiming (p. 248).

20.5.10 StochasticPeriodLong StochasticPeriod [get]

The interval for resetting states (in years). The user interface only allows this value to be set to 1. See also SetSimulationTiming (p. 248).

20.5.11 NumberOfTimeStepsLong NumberOfTimeSteps [get]

The number of time steps in the simulation, as follows from Simulation-Start, SimulationEnd, and TimeStep. This number is first computed in the first time step, i.e., is not available until after the first call to Simulate-TimeStep or Simulate.

20.5.12 SilentBoolean Silent [get; set]

Indicates whether any dialogs should be displayed.

20.5.13 OptimizationModeOptimizationModes OptimizationMode [get]

Determines the behavior when errors occur during any of the iterative simulations executed internally by the Optimize method (see also there).

20.5.14 SimulationDescriptionString SimulationDescription [get; set]



The simulation description as specified in the user interface, "Run MIKE BASIN" dialog. The description determines the name of the results output. If you want to set this property, you must do so before calling Initialize.

20.6 DHI_MIKEBASIN_Engine.ModelObject interface methods

The following sections outline the most commonly used interface methods for DHI_MIKEBASIN_Engine.ModelObject.

Note: You cannot create a new instance of a ModelObject. Instances can only be returned from the Engine interface, methods GetModelObject or FindModelObject (.Net interface only).

20.6.1 GetBasicInfoGetBasicInfo ByRef Long ObjectTypeAsInt, ByRef Long ObjectID, ByRef String UserDefName

Returns information common to all ModelObjects. ObjectTypeAsInt is the index in the enumeration ObjectTypes (0 = RiverNode, etc). This method avoids using the enumeration itself in order to be generic. ObjectID is the primary key value in the attribute table for the object, which is the field DHI_ID. Note that every ModelObject has a DHI_ID, not just features. User-DefName is the name, as entered in the "Name" field in feature's property dialog, the Water Quality parameter set dialog, or the "Comment" field of an allocation rule, depending on the type of model object.

20.6.2 FindResultIndexLong FindResultIndex String Name

Simulation results are generated for every ModelObject that is a feature or network element. FindResultIndex returns the index (zero-based) within all result items available for a ModelObject. This index can be stored in a local variable and used repeatedly to access results in a fast manner.

For example, all nodes have a result time series item "Net flow to node". Furthermore, in the output, the item name is prepended an ID letter and the feature ID for easier identification, eg., "N15|Net flow to node". This method should be called without the prepended part, i.e., with "Net flow to node" alone.

20.6.3 GetCurrentResultDouble GetCurrentResult Variant NameOrZeroBasedIndex

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Get the current (this iteration's or time step's) value of a results item for the ModelObject, which must be a feature / network element. Thus, Get-CurrentResult is relevant only when the macro takes control of the simula-tion time loop by using SimulateTimeStep or AdvanceTimeStep on the engine. The return value is in user units, which are the units also shown in the results time series (not necessarily SI).

GetCurrentValue is very useful when modeling feedback, e.g., the sensi-tivity of water demand to availability. Given the "Relative deficit" current result, you could use SetInput to manipute the "Water demand" input time series, then run the current time step again until some convergence crite-rion you define is attained, and finally call AdvanceTimeStep.

The argument NameOrZeroBasedIndex can be a string (as used in Find-ResultIndex) or a long (as would be returned by FindResultIndex). Using the long is faster.

20.6.4 GetAverageResultDouble GetAverageResult Variant NameOrZeroBasedIndex, Date Start-Time, Date EndTime

Get any period's (reasonably ending before the current time in the simula-tion) time-weighted average value of a results item. The value is in user units (not necessarily SI). The argument NameOrZeroBasedIndex can be a string (as used in FindResultIndex) or a long (as would be returned by Fin-dResultIndex). Using the long is faster. The arguments StartTime and End-Time delimit the period of interest.

20.6.5 FindInputIndexLong FindInputIndex String DatabaseFieldName, String TSGroupItem-Name

This method is similar to FindResultIndex, but for inputs. Inputs are more complex than results, because they can be not only time series, but also lookup tables and parameters. You will generally not write code that calls this method, but have the Macro Assistant generate it for you, or use Get-InputSpecs to retrieve the database location details. There is also an option in the Macro Assistant to show the database location specs (the two argu-ments to this method) as tooltips when you move the mouse over the cor-responding tree view node.

The argument DatabaseFieldName indicates the field in the attribute table where an input is set. The argument TSGroupItemName indicates the time series item name (if any) within a time series input group. The return value is the zero-based index found.



20.6.6 GetInputSpecsBoolean GetInputSpecs Long iQuantityZeroBased, ByRef String Database-FieldName, ByRef String TSGroupItemName, ByRef String DisplayName, ByRef Long EumUnit, ByRef String QuantityDescription

This method is similar to GetResultSpecs, but for inputs. The return value is true if a result item with the requested index exists, false otherwise. Thus you can use a while loop to retrieve information on all inputs for the ModelObject.

DatabaseFieldName is set to the name of the field in the object's attribute table that - in a regular simulation - defines the input quantity. If this field refers to a time series group or XY lookup table, TSGroupItemName is set to the name of the item within the group. It is set to an empty string if the input quantity is a parameter. DisplayName and QuantityDescription are set to a textual descriptions, the latter containing more details. EumUnit is set to the DHI-internal code for the unit of the input quantity.

20.6.7 GetInputOriginalValueDouble GetInputOriginalValue Long iQuantityZeroBased, Variant Time-SeriesStartTimeOrTableRow, Variant TimeSeriesEndTime

Return the value of a quantity with index iQuantityZeroBased as it would be in a regular simulation, i.e. as set during Initialize().The value is in the same unit as displayed in the user interface. If the quantity is a time series, you can use pass Date values in the arguments TimeSeriesStartTimeOrTa-bleRow and TimeSeriesEndTime to retrieve a value for a sub-period only. If the quantity is a lookup table, you can use pass a Long value in the argu-ment TimeSeriesStartTimeOrTableRow to indicate the row (zero-based).

GetInputOriginalValue is useful, for example, when wanting to set an input to a multiple of its otherwise user-defined "base" value, or to find an initial guess in an optimization.

20.6.8 SetInputSetInput Long iQuantityZeroBased, Variant TimeSeriesStartTimeOrTable-Row, Variant TimeSeriesEndTime, Double valueInUserUnits

This is the single method for setting any input to a MIKE BASIN simula-tion. The index iQuantityZeroBased is the index found with FindInputIndex or GetInputSpecs. If the quantity is a time series, you can use pass Date values in the arguments TimeSeriesStartTimeOrTableRow and Time-SeriesEndTime to manipulate a sub-period only. If the quantity is a lookup table, you can use pass a Long value in the argument TimeSeriesStart-

256 MIKE BASIN

Lesser used DHI_MIKEBASIN_Engine.ModelObject methods

TimeOrTableRow to manipulate a single row (zero-based). The value to be set is in the same unit as displayed in the user interface.

Note that if the quantity is a time series, only values in existing time steps can be changed. If the arguments TimeSeriesStartTimeOrTableRow and/or TimeSeriesEndTime do not match perfectly any existing time step in the input time series, the closest ones will be used instead. Thus, be aware that if you would like to use a macro to set daily inputs, you cannot use a monthly time series in the regular simulation input. Also note that there is no recycling for SetInput. In other words, while it is generally fine in MIKE BASIN to specify an input time series for any year (as long as it covers a whole year), you must call SetInput with the actual year in the time series.

20.7 Lesser used DHI_MIKEBASIN_Engine.ModelObject methods

20.7.1 GetExtendedInfoGetExtendedInfo ByRef ObjectTypes ObjectType, ByRef String UserDef-Name, ByRef String UserDefCategory, ByRef Long ObjectID, ByRef Long FeatureID, ByRef RuleTypes RuleType

This is an extended version of GetBasicInfo. The ObjectType is returned as the (more indicative) enumeration element. ObjectID and UserDefName are returned as in GetBasicInfo. UserDefCategory is the Category input available for all features / network elements, but not rules or water quality models. Also FeatureID is only relevant for features. It is the ID within the feature class. MIKE BASIN generally divides feature class tables and attribute tables, with a 1:1 relationship between them. The feature classes for all nodes is DHI_NodeFeatures, for reaches it is DHI_BranchFeatures, and for catchments it is DHI_Catchment. RuleType is the type of allocation rule, relevant only if the ModelObject is a Rule.

20.7.2 GetResultSpecsBoolean GetResultSpecs Long iItemIndexZeroBased, ByRef String Item-Name, ByRef Long EumDataType, ByRef Long EumUnit

In a way, this is the inverse of FindResultIndex, in as much that for a given index, the result item name is returned. Also returned are DHI-internal IDs for the data type and unit, respectively. The return value is true if there exists a results item with the requested index, false otherwise. Thus you can use a while loop to retrieve information on all results for the ModelOb-ject.



20.7.3 GetDayResultDouble GetDayResult Variant NameOrZeroBasedIndex, Date StartTime

This method is mainly maintained for backward compatibility. It returns the same result as GetAverageResult with EndTime = StartTime + 1 day.

20.7.4 GetMonthResultDouble GetMonthResult Variant NameOrZeroBasedIndex, Date StartTime

This method is mainly maintained for backward compatibility. It returns the same result as GetAverageResult with EndTime = StartTime + 1 month.

20.7.5 GetInputTSObjectTSObject GetInputTSObject Long iQuantityZeroBased

If the input quantity with index iQuantityZeroBased is a time series, this method returns the reference to the in-memory object that holds both data and supplies many advanced methods for their manipulation. Most users will not find a need to access a TSObject directly, but documentation on it can be found on www.mikeobjects.com.

20.7.6 GetOverwriteableVariableSpecsBoolean GetOverwritableVariableSpecs


20.7.7 OverwriteVariableInComingTimeStepOverwriteVariableInComingTimeStep


20.8 DHI_MikeBasin_Data enumerations

The following enumerations also used in the engine are defined in the "DHI Mike Basin Data Access Component" (DHI.MikeBasin.Data.tlb/dll)

20.8.1 ObjectTypesThe types of entities in a MIKE BASIN model: {RiverNode, WaterUser-Node, HydroPowerNode, ReservoirNode, Reach, Catchment, Rule, Exter-nalUpdater, WQModel, InvalidObject}.

258 MIKE BASIN

DHI_MikeBasin_Data enumerations

The first six members of the enumeration are also features in the map, whereas the remaining are logical entities. ExternalUpdater refers to an entity that is not yet fully implemented. InvalidObject is returned when a method cannot determine the proper value.

20.8.2 WqSimulationModesThe types of water quality simulation options in MIKE BASIN: {NoWq, AllSolutes, AllSolutesExceptDO}.

20.8.3 OptimizationModesThe options for how to handle errors in each of the iterative simulations executed in an optimization. One of {NoOptimization, IgnoreIterationErr-ors, ReportIterationErrors, QuitOnIterationErrors, ReportIterationError-sAndWarnings}. IgnoreIterationErrors is the most robust option. ReportIterationErrorsAndWarnings is not available from the user inter-face.

20.8.4 RuleTypesThere are about 20 different types of allocation rules, e.g. Supply_Demand, Supply_ManagedDemand, or Call_Demand. Detailed documentation of those is beyond the scope of this document, and the enu-meration is used in only one minor method.



260 MIKE BASIN

Tables

21 MIKE BASIN DATA MODEL The following information is provided for advanced users or developers who might want to understand the inner workings of MIKE BASIN, or who might want to build database applications on top of MIKE BASIN.

21.1 Tables

The MIKE BASIN (MB) network contains 6 types of objects. Their data are generally stored in a Feature Class table and a 1:1-related attribute table. The details can be seen in Table 21.1.

Notes

River nodes and reservoirs can be the outlet of a catchment, in which case they display in a different color on the map.

As can be seen, all node types have a common feature class. This means that the FeatureID is unique across all DHI_MbXXXNodes tables.

The DHI_ICMParameterSets attributes are only used when modeling groundwater. For most simulations, all attributes are in DHI_Catchment. This is so because DHI_Catchment is also used by the NAM rainfall-runoff model.

The table DHI_WQSurfaceWaterParameterSets contains numerical parameters for water quality simulations.

The table DHI_MbSimulation contains the execution settings. It must have exactly 1 row.

The table DHI_MbAllocationRules contains operation and allocation logic.

Table 21.1

Network Object Feature Class Attribute TableRiver Node DHI_NodeFeatures DHI_MbRiverNodes

Hydropower Node DHI_MbHydroPowerNodesWater User Node DHI_MbWaterUserNodesReservoir Node DHI_MbReservoirNodes

Reach DHI_BranchFeatures DHI_MbReachesCatchment DHI_Catchment DHI_ICMParameterSets


MIKE BASIN data model

21.2 Relationships

MIKE BASIN uses the ArcObjects-manipulated primary key OBJECTID only in a single relationship, for a feature class. MIKE BASIN’s own rela-tionships use DHI_ID as the primary key.

The relationships between Feature Class and attribute table are:

[FeatureClass].OBJECTID <--- (1 : 1)--> [Attribute table].FeatureID

Note that the relationship class NodesHasCatchments that is part of MB's template database is no longer used.

The [Attribute table].OBJECTID key is not used in any relationship.

There are a few relationships using DHI_ID:

[DHI_MbReaches]. WQParameterSet <- (n:1)-> [DHI_WQSurfaceWaterParameterSets].DHI_ID

[DHI_MbReservoirs]. WQParameterSet <-(n:1)-> [DHI_WQSurfaceWaterParameterSets].DHI_ID

For time series associations, handled by the Time Series Manager

[FeatureClass].DHI_ID <--- (0..1 : n)--> [DHI_Sensor].FeatureID

In MIKE BASIN’s data access layer, there is a component called IDMan-ager that ascertains that DHI_ID is unique in every table that uses it. It does so by storing the highest DHI_ID in every table in the meta table DHI_IDManager. So when adding a row to any such table, the IDManager should be called to increment that number. Although in general the idea is to only let the IDManager manipulate "its" table DHI_IDManager, an import procedure should probably access it directly.

21.3 Topology

In the ArcMap user interface, MIKE BASIN uses a geometric network. The DHI_BranchFeatures and DHI_NodeFeatures feature classes partici-pate in the geometric network. A geometric network consists of line fea-tures (called "edges") and node features (called "joints") and a set of system tables which keeps track of how these features are connected. The system tables are maintained by ArcObjects and are not directly accessi-ble. In addition, the geometric network will automatically recalculate the

262 MIKE BASIN

Topology

topology dynamically as the network is edited and new nodes and branches are added or removed.

Because we want to be able to run simulations without the user interface, i.e., without an ESRI license, the network topology is also stored in the attribute tables. During an edit session in ArcMap, our network editor extension always keeps the relevant relationships in synch. All network topology can be described based on the IDs of the nodes alone, and here it becomes important that FeatureID is unqiue across all node types' attributes tables! The relationships are:

[Node Attribute table].FeatureID <--- (1 : 0..n)--> [DHI_MbReaches].UpstreamNode

[Node Attribute table].FeatureID <--- (1 : 0..n)--> [DHI_MbReaches].Down-streamNode

[Node Attribute table].FeatureID <--- (1 : 0..n)--> [DHI_Catchment].OutletN-ode

[Node Attribute table].FeatureID <--- (1 : 0..1)--> [DHI_Catchment].Upper-Node

In other words, and with details on restrictions:

A river or reservoir node can have any number of downstream nodes, of which only at most one may be a river or reservoir node. A special case is a river's natural bifurcation, which is represented by a river node with exactly two downstream river nodes.

A hydropower node must have exactly one downstream node, either a river node or a reservoir node.

A reservoir node can have at most one hydropower node downstream.

A water user node can have any number of river nodes, reservoir nodes, or water user nodes downstream and upstream.

A node can have any number of upstream nodes. A hydropower node, however, must have exactly one upstream node that is a reservoir node.

A node can be the outlet of any number of catchments.

A reach has exactly one downstream node and one upstream node.

A catchment has exactly one outlet node, and possibly one upper node. The upper node of a catchment can be any node inside the catchment upstream of the outlet (strictly, the upper node is only needed for water quality calculations).



A "logical topology" exists for the allocation and operation rules, as those define the flow rules between two nodes (upstream/downstream) or at one node (by convention, the downstream node). The relationships are:

[Node Attribute table].FeatureID <--- (0..1 : 0..n)--> [DHI_MbAllocationRules].UpstreamNode

[Node Attribute table].FeatureID <--- (1 : 0..n)--> [DHI_ MbAllocationRu-les].DownstreamNode

21.4 Physical Values (Units)

Many tables contain numbers that represent physical quantities that as such have a unit. Such number fields are characterized by being of type double. MIKE BASIN has a component called DatabaseManager that uses a meta table to store units for every field of type double in every table. This table, DHI__MetaDoubles, also contains data type, default values, and any bounds for a valid range.

DHI has an Engineering Unit Management dll (eum.dll) in which units and data types are represented by numerical ID's. The fields eumUnit, DefaultUnitSI, and DefaultUnitUS in DHI__MetaDoubles contain such ID's. For legibility only, the fields eumUnitSIAsString and eumUni-tUSAsString contain the string representation of the ID's.

When a MIKE BASIN project is created, the DHI__MetaDoubles table is automatically copied from a template database to the new project data-base. It is thus possible also for an "empty" database to see what units to assume for fields in attribute tables that hold physical quantities.

21.5 Time series and XY-type lookup tables

Many fields in the MIKE BASIN attribute tables refer to time series or lookup tables. Technically, DHI's TSObject underlies both proper time series and lookup tables (the latter are represented as a "time series" with an "x" instead of a time axis). For this reason, but maybe somewhat con-fusing, also lookup tables are treated as time series in the DHI data model.

Some details on the DHI time series data model are helpful in understand-ing its use in the MIKE BASIN data model. The data model defines a time series as a pair of a time (or "x") column and a single column of values. A time series group is defined as a collection of any number of time series. A time series can be a member of at most one group. Time series may be

264 MIKE BASIN

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stored locally in the database, or remotely, eg as files. The dfs file format mostly used by DHI supports multiple value columns for a single time col-umn. In the data model, files are usually represented as time series groups. However, conversely, a group need not be stored as a single file! Also, it is possible to have lookup tables with more than one "y" column, e.g, the level-area-volume table in MIKE BASIN.

Fields in the attribute tables ending with "TS" refer to time series, and fields ending with "Table" refer to lookup tables. Such fields are of type integer, which indicates their group ID in the DHI time series data model, i.e., DHI_TimeSeriesGroups.DHI_ID, as related to DHI_TimeSeries.GroupID.

To be valid simulation input, time series groups must contain particular items. For example, the field DHI_Catchment.TotalRunoffTS must indi-cate a group that contains an item of type discharge or specific runoff (data types are also as defined by DHI's Engineering Unit Management dll). The MIKE BASIN data access component provides valid group defini-tions through static methods.



266 MIKE BASIN

I N D E X

267

Index

AAnimation . . . . . . . . . . . . . . . 141ArcGIS extension . . . . . . . . . . . . 12

BBackwater . . . . . . . . . . . . . . . 111Bifurcation Node Dialog . . . . . . . . 63

CCatchment Dialog, General . . . . . . 71Catchment Dialog, WQ in Groundwater

77Crop Sequence . . . . . . . . . . . . 126Crop Yield . . . . . . . . . . . . . . . 114

DDead Storage . . . . . . . . . . . . 90, 92Decay Rates Editor . . . . . . . . . 190Delineating catchments . . . . . . . . 67Dual crop coefficient model (FAO56) .

124

EEngine efficiency . . . . . . . . . . . 110EUM . . . . . . . . . . . . . . . . . . . 35

FF1 key . . . . . . . . . . . . . . . . . . 11FAO 33 Yield Model . . . . . . . . . 126FAO 56 Climate model . . . . . . . 121FAO 56 Irrigation Model . . . . . . . 123FAO 56 Soil Water Model . . . . . . 123FAO56 Reference ET . . . . . . . . 121Flood Control level . . . . . . . . . . . 92Flood Control Zone . . . . . . . . . . 93Flow capacity time series . . . . . . . 49Flow losses . . . . . . . . . . . . . . . 48

GGroundwater . . . . . . . . . . . . 72, 84

HHead Approximation . . . . . . . . . 111Hydropower . . . . . . . . . . . . . . 109Hydropower Dialog . . . . . . . . . . 109

IInstalled capacity . . . . . . . . . . . 110Irrigation . . . . . . . . . . . . . . . . 113Irrigation Dialog, Groundwater . . . 120Irrigation Dialog, Scheme . . . . . . 116Irrigation Dialog, Surface Water . . 119

LLinear Reservoir model . . . . . . . . 73Load Calculator Dialog . . . . . . . . 169Load Calculator, Distance Decay . . 180Load Calculator, Domestic Source . 173Load Calculator, Fertilizer Source . 172Load Calculator, Livestock Source . 172Load Calculator, Output . . . . . . . 191Load Calculator, Point Source . . . 174Load Calculator, Transport General 179Load Catchment Properties Editor . 187Load Reduction Factors Editor . . . 178Load Source Fluxes Editor . . . . . 177Load Sources Editor . . . . . . . . . 177

MMacro Assistant . . . . . . . . . . . . 144Maximum release constraint . . . . . 92MIKE BASIN Result Groups . . . . . . 32Minimum Flow Rule . . . . . . . . . . 62Minimum operation level . . . . . . . . 92Minimum release reqiurement . . . . 92

NNAM . . . . . . . . . . . . . . . . . . 211

Accumulation and melting of snow . 220Adjustment of temperature and pre-cipitation to altitude zones . . . . 223Altitude-distributed snowmelt model 221Base temperature (snow/rain) T0 231Baseflow . . . . . . . . . . . . . . 218Baseflow time constant CKBF . . 229Basic modelling components . . 216Capilary flux . . . . . . . . . . . . 219Degree-day coefficient Csnow . . 231Evapotranspiration . . . . . . . . 216

268 MIKE BASIN

Index

Extended groundwater components .218Extended snow melt components 225Groundwater depth for unit capillary flux GWLFL1 . . . . . . . . . . . . 230Groundwater recharge . . . . . . 218Initial conditions . . . . . . . . . . 232Interflow . . . . . . . . . . . . . . 217Interflow and overland flow routing .217Lower groundwater storage . . . 219Lower zone or root zone storage 216Maximum groundwater depth causing baseflow GWLBF0 . . . . . . . . 230Maximum water content in root zone storage Lmax . . . . . . . . . . . 226Maximum water content in surface storage Umax . . . . . . . . . . . 226Model parameters . . . . . . . . . 225Model Structure . . . . . . . . . . 214Overland flow . . . . . . . . . . . 216Overland flow runoff coefficient CQOF . . . . . . . . . . . . . . . . 227Radiation coefficient Crad . . . . 231Rainfall degree-day coefficient Crain231Ratio of groundwater catchment to topographical catchment area Carea229Recharge to lower groundwater stor-age CQLOW . . . . . . . . . . . . 229Root zone threshold value for ground-water recharge TG . . . . . . . . 229Root zone threshold value for interflow TIF . . . . . . . . . . . . . . . . . 229Root zone threshold value for over-land flow TOF . . . . . . . . . . . 228Shallow groundwater reservoir description . . . . . . . . . . . . . 219Snow module . . . . . . . . . . . 220Soil moisture content . . . . . . . 218Specific yield SY . . . . . . . . . 230Structure of the altitude-distributed snowmelt module . . . . . . . . . 221Surface storage . . . . . . . . . . 216

Time constant for interflow CKIF . 227Time constant for routing interflow and overland flow CK12 . . . . . . . . 227Time constant for routing lower base-flow CKlow . . . . . . . . . . . . . 229

NAM Elevation Zones . . . . . . . . 204NAM Ground Water . . . . . . . . . . 202NAM Initial Conditions . . . . . . . . 205NAM Overview . . . . . . . . . . . . 195NAM Snow Melt . . . . . . . . . . . . 203NAM Surface-Rootzone . . . . 200, 201New Load Source Dialog . . . . . . . 170

OOptimization . . . . . . . . . . . . . . 149Optimization Problem Dialog . . . . 149Options Dialog, Advanced . . . . . . 19Options Dialog, General . . . . . . . 18Options Dialog, Symbology . . . . . 19

Ppseudo-DEM . . . . . . . . . . . . . . 68

RReach Dialog, General . . . . . . . . 48Reach Dialog, Hydraulics . . . . . . 49Reach Dialog, Water Quality . . . . . 55Reservoir Dialog . . . . . . . . . . . . 87Reservoir Dialog, General . . . . . . 89Reservoir Dialog, Operation . . . . . 91Reservoir Dialog, Spillways . . . . . 104Reservoir Dialog, Water Quality . . . 107Result Manager . . . . . . . . . . . . 140Result presentation . . . . . . . . . . 133Return Flow . . . . . . . . . . . . . . 114Return flow . . . . . . . . . . . . . . . 83Return flow rule . . . . . . . . . . . . 83River Node Dialog . . . . . . . . . . . 59Routing . . . . . . . . . . . . . . . . . 49Rule Curves Reservoirs and Lakes . 91Run NAM Simulation . . . . . . . . . 199

SSpillways . . . . . . . . . . . . . . . . 104Surplus capacity Usage . . . . . . . 110

269

Index

Symbology . . . . . . . . . . . . . . 129

TTailwater . . . . . . . . . . . . . . . . 110

WWater Quality . . . . . . . 55, 76, 85, 107Water Quality Modeling . . . . . . . 159Water User Dialog . . . . . . . . . . . 79Water User Dialog, Groundwater . . 84Water User Dialog, Water Quality . . 85

270 MIKE BASIN

MIKEBASIN_UserManual

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