1

Introduction to Modeling Eutrophication Using

QUAL2Kw

Nicholas von Stackelberg, P.E.December 4, 2012

Slide 2

QUAL2Kw Background

Developed specifically to simulate dissolved oxygen dynamics in riverine systemsWidely applied to eutrophication TMDLs and WLAs in the US and internationallyDevelopers

Dr. Steven Chapra, Tufts UniversityGreg Pelletier, Washington Dept of EcologyMaintained and distributed by Washington Dept of Ecology

Related ModelsQUAL2E – Brown and Barnwell 1987QUAL2K – distributed by EPA

2

Slide 3

QUAL2Kw Fundamentals

Receiving water model – simulates flow and kinetics of advective systems

One dimensional - channel is uniformly mixed vertically and laterally

Steady state flow - non-uniform, steady flow is simulated

Diel meteorology & water quality – Meteorology and water quality constituents can be varied over 24-hours

Flow and water quality inputs - Point and non-point loads and abstractions can be simulated

Water quality kinetics – temperature, pH, sediment, pathogens, nutrients, organic matter, algal growth and dissolved oxygen

Slide 4

QUAL2Kw Limitations

Does not simulate:Watershed processesNon-uniform mixing – 2D or 3D transport

Unsteady flowBeta version with non-steady, non-uniform flow using kinematic wave flow routing now availableScour and depositionAdsorption/desorption to sedimentOrganisms – zooplankton, macroinvertebrates, fish

Reservoirs

3

Slide 5

Mechanistic Model

Conservation of MassFor a finite volume over a unit time period:

Accumulation = Loading – Outflow +/- Reaction - Settling

loading outflowaccumulation

settling

Slide 6

Dry weather – no precipitationHeadwaters (hourly)

Point Sources (sine wave)TributariesWastewater treatment plantsIndustrial discharges

Point Abstractions (sine wave)Canals/diversions

Diffuse Sources (sine wave)Groundwater

Model Inputs

19

21

6:00 12:00 18:00 0:00 6:00

Time of max = 17:13

Mean = 20.057

Range/2 = 0.717

20

4

Slide 7

Model Segmentation

Point withdrawalPoint withdrawal

Headwater boundary

Downstream boundary

1

2

3

456

8

7

Nonpointwithdrawal

Nonpointsource

Point withdrawal

Point source

Point source

Point source

Slide 8

Flow (Q)→ depth (H) and velocity (U)

Hydraulics

Given Q: solve for H and U• Rating Curve• Mannings Equation for Trapezoidal Channel• Weir Equation

Reach worksheet

5

Slide 9

Trapezoidal Channel

B0

1 1ss1 ss2

H

Q, U

S0

Mannings Equation

3/2

3/52/10= c

PA

nS

Q

Solves for H and U, given Q, S0, B0, ss

Slide 10

∑=

=i

kkitt

1, τ=

k

kk Q

Uτ

Travel Time

Jordan River (10/3/2006) Mainstem

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

2030405060708090

trav time, d Travel time data (d)

6

Slide 11

Heat Balance

iinflow outflow

dispersion dispersion

heat load heat withdrawal

atmospherictransfer

sediment-watertransfer

sediment

Slide 12

Water Surface Heat Balance

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Slide 13

Meteorological Data

( )

))(())((15273(

)1(031.015273(

airair14

4air

eeUfTTUfc).T

ReA).TJJ

swsws

Lairsn

−−−−+−

−+++=

εσ

σ

Solar Radiation(Cloud Cover)

Dew PointTemperature

WindSpeed

AirTemperature

Slide 14

Shading

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Slide 15

TTools for ArcGISOregon DEQ

http://www.deq.state.or.us/WQ/TMDLs/tools.htm

Shade.xls Excel SpreadsheetWashington DOE

http://www.ecy.wa.gov/programs/eap/models.html

Shading Estimation Tools

Slide 16

Water Quality Constituents

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Slide 17

= i

Hv

Inorganic Suspended Solids

ISS Settling

vi: ISS settling velocity

H: water depth

* ISS

Slide 18

Dissolved Oxygen

10

Slide 19

Effect of Water Velocity (8 formulas)

Effect of Wind (2 formulas)

Reaeration

Slide 20

Soluble Carbonaceous BOD

DO

kdc

SCBODs SCBODfkhc

kdcs

SCBODs SCBODf

DO

kdckhc

Series:kdcs= 0

SCBODs SCBODf

DO

kdckhc= 0

kdcs

Parallel:khc= 0

2 Types of SCBOD:SCBODs: slow reacting

SCBODf: fast reacting

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Slide 21

Detritus (Particulate Organic Matter)

Settling

kdcSCBODs SCBODfkhckdcs

kdt rod

Ff

1 – Ff

Detritus

DO

DO

SOD

vdt

Dissolution

Algae

Death kdp

Slide 22

Nutrient Cycle

respiration

death

photosynthesisphytoplankton

nitrification denitrificationnitrateammoniaorg N

hydrolysis

org P inorg Phydrolysis

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Slide 23

Nitrogen

air

water

mineralization

organic N NH4+ NO2

− NO3−

nitrification nitrification

O2

O2,s

net production

N2

nitrogen fixation

N2,s

NH3

highpH

lowpH

gas-filmcontrolled

volatilization

liquid-filmcontrolled

volatilization

settling

denitrification

denitrification

Slide 24

Nitrification (NBOD)

CBODs

Ammonia N

DO

CBODf

DO

O7H2N5CO4H4NOO5CH 22232 ++→++ +−

Nitrate N

nitrification

DO is low

denitrificationkdnkn

OH2H2ONH 224 +→+++ NO 3

−+

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Slide 25

PhytoplanktonFree floating algae

Bottom AlgaeFixed to stream substratePeriphyton or benthic algaeFilamentous algaeMacrophytes

Algal Growth

Slide 26

Floating vs. Bottom Plants

Floating BottomTransport Yes No

Types DiatomsGreensBlue Greens

PeriphytonFilamentous AlgaeRooted Macrophytes

Units mgA/m3 gA/m2

Light Ave. Water Column Bottom Light

Predation Zooplankton Insect Larvae, Snails

Substrate None Rock vs. Mud

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Slide 27

dadt

= transport + kg(T, N, I) a – kr(T) a – kd(T) a – (vs/H) a

Phytoplankton Kinetics

temperature

respirationdadt

= transport + kg(T, N, I) a – kr(T) a – kd(T) a – (vs/H) a

settling

death

kg(T, N, I) = kg,T φN φL

inorganicnutrients

detritusorganic nutrients

sedimentslightnutrients

growth

Slide 28

Phytoplankton StoichiometryThe “Redfield Ratio”

100% : 40% : 7.2% : 1% : 0.5-2.0%

D : C : N : P : A

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Slide 29

Light Estimation

(a) floating plants (b) bottom algae

Slide 30

Periphyton Growth Rates

Cgb(T) = mgA/m2/d

kgb(T)ab = mgA/m2/d

)(= LbNbgbb Tk

dtda φφ ab

First-order:

)(= LbNbgbb TC

dtda φφ

Zero-order:

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Slide 31

1 mm

10 mm

POM CBOD Ammonia Nitrate Inorganic Phosphorus

Sediment Oxygen Demand

Slide 32

QUAL2K2w User Manual (Version 5.1), Greg Pelletier and Steve Chapra, 2008.QUAL2K2w Theory and Documentation (Version 5.1), Greg Pelletier and Steve Chapra, 2008.Hydrodynamics and Water Quality: Modeling Rivers, Lakes and Estuaries, Zheng-Gang Ji, John Wiley and Sons, 2008.Surface Water Quality Modeling, Steven Chapra, WCB McGraw Hill, 1997.Principles of Surface Water Quality Modeling and Control, R.V. Thomann and J.A. Mueller, Harper and Row, 1987.Sediment Flux Modeling, Dominic DiToro, John Wiley and Sons, 2001.The Enhanced Stream Water Quality Models QUAL2E and QUAL2E-UNCAS: Documentation and Users Manual, L.C. Brown and T.O. Barnwell, EPA/600/3-87-007, 1987.

References