Water Quality Modeling Workshop, HWorkshop, H- · PDF file1 Water Quality Modeling Workshop,...

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Water Quality Modeling Water Quality Modeling Workshop, HWorkshop, H--GAC:GAC:M d li F d t lM d li F d t lModeling FundamentalsModeling FundamentalsTim Cox, Ph.D., P.E.Tim Cox, Ph.D., P.E.

CDMCDM

June 30, 2010June 30, 2010

Session OutlineSession Outline

Modeling Overview

Stream Water Quality Modeling

Lake Water Quality Modeling

Estuary Modeling

Watershed Modeling

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Modeling OverviewModeling Overview

Modeling OverviewModeling OverviewWhy do we use models?Why do we use models?

To predict the future

To quantify things that are difficult (or expensive) to directly measure

To gain a better understanding and interpretation of existing measured data.

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Modeling OverviewModeling OverviewTypical Applications of Water Quality ModelsTypical Applications of Water Quality Models

TMDLs

BMP assessment

Compliance demonstration

Data interpretationData interpretation

Modeling OverviewModeling OverviewModel Limitations and Sources of ErrorModel Limitations and Sources of Error

Measurement error data inputscalibration

Numerical errorstability t titruncation error

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Modeling OverviewModeling OverviewModel Limitations and Sources of ErrorModel Limitations and Sources of Error

Structural errornot comprehensive enoughmissing key processes or structures

Operator errorbad model selectionbad calibrationbad calibrationbad application or extension

Modeling OverviewModeling OverviewModel CategoriesModel Categories

Mechanistic

Qin = CIA + baseflow

Cin = EMC, Cbase

Qout = Qin

[Chl a]

fd fp Evap

[N1]Qsup , Csup

kd

[P1]

Phytoplankton = F(N1, P1, d1, V1 )

Qrecirc

vS

[N2] ,[P2] [N3],[P3]kd3

kd2

Linternal = D *AdzdC

d2

kdz

V2= ρ*d2*A

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Empirical

7 Day Low Flow vs Total Water Year Precip:

y = 10.97e0.05x

R² = 0.8480

100

120

140

160

180

7Q (cfs)

7 Day Low Flow vs. Total Water Year Precip: Kaweah River

0

20

40

60

0 10 20 30 40 50 60

7

total precipitation (in.)


Deterministic

C XC1 = XC2 = Y...

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ProbabilisticDistributions of 7Q10 Low Flows:

15

20

25

307Q

10 (cfs)

Kaweah River, 3 Rivers CA

Historical Data 7Q10 = 18 cfs

0

5

10

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

7

Risk of Lower 7Q10

A2 Climate Change B1 Climate Change Historical Distribution Bootstrapping


Probabilistic

a.) Modeled Exceedance Probability CDF:24-hour Storm Events

0 4

0.6

0.8

1

of e

xcee

danc

e

10 yr Post 10 yr Pre5 yr Post 5 yr Pre2 yr Post 2 yr PreAcute Standard (160.3) *

0

0.2

0.4

0 2000 4000 6000 8000 10000 12000

C (ug/l)

prob

abili

ty

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Modeling OverviewModeling OverviewModel Calibration and VerificationModel Calibration and Verification

1 6

Machado Lake Phosphorus

M-1 M-2 M-3 modeled

0 6

0.8

1.0

1.2

1.4

1.6

TP (m

g/l)

0.0

0.2

0.4

0.6

9/25/2007 1/3/2008 4/12/2008 7/21/200810/29/2008 2/6/2009 5/17/2009 8/25/2009 12/3/2009date

Modeling OverviewModeling OverviewModel SelectionModel Selection

Intended Use

Relative, Current Absolute, Current Relative, Future Absolute, Future

single param

multiple params

single param

multiple params

single param

multiple params

single param

multiple params

Model Complexity1D -> 3D

Simple, Empirical

Multi-Variate, Empirical

Lumped, Mechanistic

Distributed, Mechanistic

1D > 3D

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Model ParameterizationModel Parameterization

Site Specific Measured Inputs

Internal Parameter Calibration

Internal Parameter Calibration + Verification

Estimated or Regional Measured Inputs


Intended Use


single param

multiple params

single param

multiple params

single param

multiple params

single param

multiple params


Simple, Empirical


Lumped, Mechanistic


1D > 3D

9







= high cost + high data requirements!


Intended Use


single param

multiple params

single param

multiple params

single param

multiple params

single param

multiple params


Simple, Empirical


Lumped, Mechanistic


1D > 3D

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= low cost + medium data requirements!

Stream Water Quality ModelingStream Water Quality Modeling

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Stream Water Quality ModelingStream Water Quality ModelingSolute TransportSolute Transport

U, D1200

1600

2000

2400

trat

ion advection, dispersion

0

400

800

1200

0:20:00 0:30:00 0:40:00 0:50:00

time (min.)

conc

ent

Stream Water Quality ModelingStream Water Quality ModelingSolute TransportSolute Transport

CCQCA ∂∂∂∂ )()(LLCq

xCAD

xxCQ

tCA

+∂∂

∂∂

+∂

∂−=

∂∂ )()()(

QCQCCQ ni

ni

ni

ni

n −∂ 11)( Error ~ Δx

xQCQC

xCQ iiii

Δ=

∂∂ −− 11)( Error Δx

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Stream Water Quality ModelingStream Water Quality ModelingDissolved OxygenDissolved Oxygen

DISSOLVEDDISSOLVEDOXYGENOXYGEN

Stream Water Quality ModelingStream Water Quality ModelingDissolved OxygenDissolved Oxygen

HydraulicsHydraulics

ReRe--aerationaeration

DISSOLVEDDISSOLVEDOXYGENOXYGEN

SODSOD Plant / AlgaePlant / Algae

TemperatureTemperature

NutrientsNutrients

BOD/TKNBOD/TKNOxidationOxidation

Plant / Algae Plant / Algae Photosynthesis & Photosynthesis &

RespirationRespiration

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Stream Water Quality ModelingStream Water Quality ModelingDO, Nutrients, Plants (Eutrophication)DO, Nutrients, Plants (Eutrophication)

ModelsWASP = dynamicWASP = dynamicQUAL2E / QUAL2K = steady stateHSPF / WARMF = dynamic watershed WQ models with instream modules

http://www epa gov/ceampubl/swater/http://www.epa.gov/ceampubl/swater/

http://www.epa.gov/waterscience/basins/

http://www.epa.gov/ATHENS/wwqtsc/html/warmf.html

Stream Water Quality ModelingStream Water Quality ModelingDO, Nutrients, PlantsDO, Nutrients, Plants

Model Calibration

Typical calibration parameters:– Kinetic rates– SOD– Plant growth rates– Must have hydraulics/transport first!

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Stream Water Quality ModelingStream Water Quality ModelingPlantsPlants

Phytoplankton (floating algae)Larger rivers lakesLarger rivers, lakesChl a (mg/L)

Periphyton (attached algae)Smaller/shallower streamsChl a (mg/m2), Dry wt. (mg/m2)

Macrophytes (rooted plants)Shallower streams = emergentLarger rivers/lakes = submerged, floatingDry wt. (mg/m2)


Phytoplankton

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Periphyton


Macrophytes

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Stream Water Quality ModelingStream Water Quality ModelingNitrogenNitrogen

NITROGEN CYCLEAIRAIR

PlantsPlants

WATERWATER

Nitrate (NO3

-)DissolvedOrganic N

ParticulateOrganic NAmmonia

(NH4+)

Nitrogen

TKNTKN

Nitrification/Nitrification/OxidationOxidation

SEDIMENTSSEDIMENTS

ParticulateNNitrate Pore Water

SRPPore WaterAmmonia

Pore WaterAmmonia

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NITROGEN CYCLEWATERWATER

SEDIMENTSSEDIMENTS

ParticulateNNitrate Pore Water

Ammonia

(Aerobic)(Aerobic)

DEEP SEDIMENTSDEEP SEDIMENTSN2 Gas

(Anaerobic)(Anaerobic)Nitrate Pore Water

Ammonia

DenitrificationDenitrification

Bacteria Bacteria in in StreamsStreams

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SourcesSources

WWTPs

Wildlife, CAFOs, AFOs

Septic Systems SSO/CSO

Sediment

SSO/CSO

OUTPUT(t t h)

InIn--stream Fate and Transport stream Fate and Transport –– Planktonic Planktonic BacteriaBacteria

• WWTPs• SSOs

INPUT (From Watershed)

Bacterial removal through:• Settling• Die-off

In-StreamINPUT(Point)

(to next reach)

• Sed-associated bacteria• Runoff

Wildlif• SSOs• CSOs• CAFOs

Die off

Addition of Bacteria from:• Regrowth

• Wildlife• Septic Systems• Boat Discharge

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Bacteria Survival InBacteria Survival In--StreamStreamFactor ResultSunlight/UV Increased UV leads to die-offRadiationTemperature Temperature outside growth range leads

to die-offSalinity High salinity leads to die-offNutrient Levels Suitable levels of nutrients encourage

bacteria growthSettling/ Adsorption

Reduces numbers of suspended bacteria, can increase bacteria in sediment

Typical DieTypical Die--off Rates off Rates

Location K (day-1)kteCC −Seine River 0.10 – 17.86Seine River 0.11 – 0.81

Houston 0.92 – 2.2Various 0.12 – 8.64

Laboratory 0.39 – 0.76

ot eCC =

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Lake Water Quality ModelingLake Water Quality Modeling


Key differences (compared to streams)Mixing > advection

– wind-induced diffusion– high residence times

2-D (vertical)

Sensitivity to surface fluxes:Sensitivity to surface fluxes:– sediments– water / atmosphere interface

Stratification

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Qin = CIA + baseflow

Cin = EMC, Cbase

Ph t l kt F(N P d V )

Qout = Qin

vS

[Chl a]

fd fp Evap

[N1]Qsup , Csup

kd

[P1]

Phytoplankton = F(N1, P1, d1, V1 )

Qrecirc

[N2] ,[P2] [N3],[P3]kd3

kd2

Linternal = D *AdzdC

d2

kdz

V2= ρ*d2*A


Stratification

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30Temperature (oC)DO (mg/L)

0

1

2

3

4

5

6

7

8

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

met

ers)

3/13/2002

6/12/2002

9/25/2002

12/11/2002

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7 8 9 10 11 12

(met

ers)

( g )

9

10

11

12

13

14

15

16

Dep

th (m 9

10

11

12

13

14

15

16

Dep

th (

3/13/2002

6/12/2002

9/25/2002

12/11/2002

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Estuary and Bay Water Quality ModelingEstuary and Bay Water Quality Modeling


Key Differences (compared to stream and lake modeling)

Hydrodynamics and solute transportHydrodynamics and solute transport– Tidal advection (flow) rather than gravity advection– Bi-directional– Cyclical– High dispersion

May need to couple more sophisticated hydrodynamic model with WQ model

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Key Differences (compared to stream and lake modeling)

SalinitySalinity– Additional stratification effects

Depths and widths may require 2-D or 3-D models


1

1.5

‐1

‐0.5

0

0.5

0 1 2 3 4 5 6 7

Q

‐1.5time

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Watershed Water Quality ModelingWatershed Water Quality Modeling


Objectives:Source (load) quantification and identificationWatershed BMP assessmentLanduse / landscape changes

Key Differences (compared to water body modeling)

Dynamic hydrology -> dynamic water qualityDynamic hydrology > dynamic water qualityAdditional model parametersAdditional data requirementsImportance of sediment load

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Hydrologic Modeling Hydrologic Modeling


Mechanistic ModelingMechanistic Modeling

Wash-offBacteria loading fromwildlife, trash, etc.

Stor

age

Time

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Empirical ModelingEmpirical ModelingSite 04 Sager Creek

Event 3 Stream Levels and P Samples

0.8

1

1.2

1.4

1.6

th (f

t)

levels samples

0

0.2

0.4

0.6

3/31/06 4/1/06 4/1/06 4/2/06 4/2/06 4/3/06 4/3/06 4/4/06 4/4/06 4/5/06

dept

date / time

EMC = Ltot/Vtot

Watershed Water Quality ModelingWatershed Water Quality Modeling0

2

45,000

6,000

Rainfall (in)

6

8

10

12

14

161 000

2,000

3,000

4,000

Flow

(cfs

)

18

200

1,000

Simulated Hydrograph Observed Hydrograph Observed Rainfall

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Watershed Water Quality ModelingWatershed Water Quality Modeling1.00

Simulated TP

Observed TP

0.50

0.75

hosp

horo

us (m

g/l)

0.00

0.25

Oct Mar Aug Jan Jun Nov Apr Sep Feb Jul Dec May Oct Mar Aug Jan Jun

Tota

l Ph

Questions and DiscussionQuestions and Discussion

Water Quality Modeling Workshop, HWorkshop, H- · PDF file1 Water Quality Modeling Workshop,...

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