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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
7
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
8
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
9
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
11
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
12
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
−+
13
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
14
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
15
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:
16
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