Introduction to Hydrological Modellingcss.escwa.org.lb/sdpd/riccar/meeting_docs/2-3.pdf · Source:...

Introduction to Hydrological Modelling

Key Issues & Implication of Climate Change on Hydrological Modeling and Policy

George J. Nasr,

ESCWA Consultant

26-Jun-13 Introduction to Hydrological Modelling 2

How does it all fit in?Policy Makers

Managers Hydrologists Issues


Outline1. Hydrologic Cycle and Watersheds2. Weather and the Hydrologic Cycle3. Hydrologic Modeling4. The Modeling Process

1

Hydrologists


Stages of the Hydrologic Cycle• Elements of a

Hydrological Model:

1

Source: http://www.dcr.virginia.gov/stormwater_management/documents/Chapter_4.pdf

– Precipitation– Infiltration– Interception– Storage

– Run-off– Evaporation– Transpiration– Groundwater


Key Unit: Watershed

Source: http://www.ourwatershed.ca/swp/watersheds.php

1


Concepts: Watershed Divide

Source: http://echo2.epfl.ch/VICAIRE/mod_1`a/chapt_2/text.htm

1


Concept: Karst Formations

Source: http://www.nzap.ca/graphics/karst_cave.jpg

1• Flow path routes:

– Converging conduits,– Unrelated to

topography

• Flow velocities: – Comparatively Fast

• Macropores/swallow holes;– Recharge bypasses the

filtering capability of soil

– Little/No filtration


Characteristics of watershed• Size: Rainfall received, retained, amount of runoff ...• Shape: Morphological parameters (geological structure),• Slope: Rainfall distribution and movement,• Drainage: Flow characteristics, erosion,• Soil: Infiltration rates,• Land use, land cover: Overland flow of the rainwater,• Main channel and tributaries: Stream flow,

1


Outline1. Hydrologic Cycle and Watersheds2. Weather and the Hydrologic Cycle3. Hydrologic Modeling4. The Modeling Process

2

Issues


Weather and the Hydrologic Cycle• Weather: day-to-day temperature and precipitation activity, • Climate: average atmospheric conditions over 30-yr periods

2

Source: Gleckler, P. J.; Taylor, K. E.; Doutriaux, C.; 2008: Performance Metrics for Climate Models, Journal of Geophysical Research, Vol. 113.

While the weather of a given day cannot be predicted in the far future, the change in prevailing future climate trends can be forecasted with relative accuracy


Climate Change and the Hydrologic Cycle2


Outline1. Hydrologic Cycle and Watersheds2. Weather and the Hydrologic Cycle3. Hydrologic Modeling

• Problem Structure• Model Types

4. The Modeling Process

3

Hydrologists


Model: Problem Structure3


Models: Spatial Scale3


Models: Time Scale

Diminished Surface Flow

DepletedGroundwater

Time span

Scale

Small Turbulent Eddies

Thunderstorms

2000 km

Seconds Minutes Hours

mic

rosc

ale

mes

osca

leSy

nopt

icG

loba

l

200 km

20 km

2 m

Days Weeks

Winds:Land/SeaMountain/Valley

HurricanesTropical Storms

Weather Fronts

Months Years

Droughts

Floods

Seawater Intrusion

Sea Level Rise

Weather Phenomena Climate ImpactsLegend:

Hydrological Impact

3


Outline1. Hydrologic Cycle and Watersheds2. Weather and the Hydrologic Cycle

3. Hydrologic Modeling• Problem Structure• Model Types:

• Conceptual • Mathematical: Forecasting / Simulation

4. The Modeling Process

3

Hydrologists


Models • Conceptual

– Qualitative, usually based on graphs– Represent important system: components, processes,

linkages, Interactions– used as:

• Initial step;– Hypothesis testing– Mathematical model development

• Framework– Future monitoring , research, management actions.

• Mathematical– Representation of real world structure, phenomena,– Addresses wide range of conditions,– Forecasting impacts of changing climatic conditions

3


Conceptual Model: Example3


Mathematical Model: Basic Structure

Source: http://www.nptel.iitm.ac.in/courses/105101002/1

3


Mathematical Models: Discretization3


Conceptual Model: Discretization Steps3


Types of Mathematical Models1. Hydrological simulation model:

– Synthesizing a (continuous) record of some hydrological variable

– for a period of time– from available concurrent records of other variables

2. Hydrological forecasting model– Synthesizing a record of some hydrological variable– or Estimating some of its states – in an interval of time– from available records of:

• The same variable • Other variables• Obtained in a an immediately preceding time period

Hydrological simulation can operate in a "forecasting mode" if estimates of the predictors for the forecast time interval are available through an independent forecast.

3


Hydrologic Simulation ModelModel Selection: study objectives, watershed

characteristics, data availability, project budget .

1. Equations:• Governing hydrologic processes,

2. Maps:• Delimit/Define the study area

3. Database: • Model parameters• Data on study area• Climatic Variables

3

Hydrologic Simulation Model

Equations Maps Database


Input: (2) Map Data

Source:http://www.isiimm.agropolis.org/OSIRIS/satellite_image/lbLit_FAOProject_5VillagesOfCnal900.jpghttp://daac.ornl.gov/LBA/guides/CD06_Landuse_Landcover_Map.png

Litani – sub-watershed

Parana

3


Input: (3) Database• Soil:

– type , texture , and structure– condition ,– Grain-size distribution,– porosity, – moisture content, capillary pressure,– Steady-state infiltration,– Saturated hydraulic conductivity,

3


Input: (3) Climactic Variables• Rainfall,• Snowfall,• Radiation,

• Humidity,• Vapour pressure,• Temperature,

3 • Sunshine hours,• Wind velocity • ...


Outline1. Hydrologic Cycle and Watersheds2. Weather and the Hydrologic Cycle3. Hydrologic Modeling4. Conclusion: The Modeling Process

4

Policy MakersManagers


Modeling ProcessConceptual Model

Mathematical Model

Computational Model

CalibrationVerification

DataModel Modification

Results

4


Model Development & Policy

Thank you

4

Introduction to Hydrological Modellingcss.escwa.org.lb/sdpd/riccar/meeting_docs/2-3.pdf · Source:...

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