Total Maximum Daily Load
(TMDL) Training Workshop
Presented by:
David W. Dilks
Paul L. Freedman
Limno-Tech, Inc.(LTI)
Ann Arbor, Ml
Don Brady
U.S. EPA
Office of Wetlands, Oceans, and Watersheds
Washington, D.C.
TMDL Workshop
-------
Total Maximum Daily Load
(TMDL) Training Workshop
Presented by:
David W. Dilks
Paul L. Freedman
Limno-Tech, Inc.(LTI)
Ann Arbor, Ml
Don Brady
U.S. EPA
Office of Wetlands, Oceans, and Watersheds
Washington, D.C.
TMDL Workshop
-------
OUTLINE
EPA's TMDL Program
TMDL Development Overview
Nonpoint Source Evaluation
Water Quality Modeling
Case Studies
Potential Pitfalls
TMDL Workshop
-------
OBJECTIVES
What is a TMDL?
What sj©ps are involved in TMDL
development?
What too Is are available for performing
those steps?
How have other TMDLs been developed?
What kind of problems can I expect?
How can I address these problems?
TMDL Workshop
-------
THEMES
New regulatory implementation of existing
technologies
Tools exist, implementation steps still
being developed
Imperfect fit between results required and
resources available
No "cookbook" solutions; professional
judgment often required
TMPL Workshop
-------
ROLE OF MODELING IN
WATER QUALITY CONTROL
Environmental
Conditions
Pollutant —> MODEL —» Pollutant
Load Concentration
Clb^lcUO)
: r\W^i
Standard
T Wastewater Load
1 liiMi'V
i (~\ Cvz_ . i o cccC
-------
TMDL DEVELOPMENT
OVERVIEW
Background
Steps of TMDL Development
Existing case studies
TMDL Workshop
-------
Effect of Nonpoint Sources on WLA
STD
WLA
Wastewater Load
0
STD
/la
WLA
Wastewater Load
TMDL Workshop
-------
TMDL: Historical change in Focus
cl/X rc_
Old Approach: r
WQS
-~
WLA
->
NPDES
Repeat for each discharge
New Approach:
WQS
|>
TMDL
WLA/LA
Ill HB»
NPDES/BMI
Consider all loads simultaneously
,-0V Ci_Jr O-o
looL^:
TMDL Workshop
-------
u
General Elements of the
Water Quality-Based Approach
1. sWp
Identification of Water
Quality-Limited Waters
o Review water quality standards
o Evaluate monitoring data
o Determine if adequate controls
are in place
5.
Assessment of Water Quality-
Based Control Actions
o Monitor point/nonpoint sources
o Audit NPS controls for effectiveness
o Evaluate TMDL for attainment of
water quality standards
4.
Implementation of Control Actions
o Update water quality management
plan
o Issue water quality-based permits
o Implement nonpoint source controls
(section 319 management
plans)
2.
Priority Ranking and Targeting
o Integrate priority ranking with other
water quality planning and
management activities
o Use priority ranking to target
waterbodies for TMDLs
Development of TMDLs
o Apply geographic approach
where applicable
o Establish schedule for phased
approach, if necessary
o Complete TMDL development
TMDL Workshop
-------
TMDL DEFINITIONS
Loading Capacity (LC):
,Vrvcc_:i"
i^Lr^V.c^Z C-*—3
The greatest amount of
pollutant loading that a
water body can receive
without violating water
quality standards.
Load Allocation (LA):
Waste Load Allocation
(WLA):
Margin of Safety (MOS):
Total Maximum Daily
Load (TMDL):
The portion of loading
capacity attributed to
nonpoint sources or
background conditions.
The portion of loading
capacity attributed to
point sources.
The portion of the loading
capacity attributed to
uncertainty. The MOS
may be explicit or implicit
via conservative
assumptions.
The sum of WLAs and
LAs and MOS.
TMDL Workshop
-------
Maximum Allowable
Nonpoint Load (LA)
Water Quality
Standard
Maximum Allowable
Point Load (WLA)
TMDL Workshop
-------
5
Determine Total Allowable Load
Define
Water Quality
Objectives
, Water Quality
H Model
V Determine Present Load
r>-\ cfZ-C. c Kc, \ Vd,\ i rXx
6 2r
Monitoring/
Nonpomt Source
Model
Total
) ~
Allowable
Load
Present
Load
(C&lbs\c (<
\^G lb-=> Ulo-o
1
3 Allocate Load Reductions
Monitoring/
Nonpoint Source
Model
Allocation
Strategy
yes
no
Load
Allocation
Wasteload
Allocation
Nonpoint Source
Load
Point Source
Load
Best Management
Practices
Point Source
Controls
Is Total
Load
(Nonpoint +
Point Sources)
Less Than
Total
Allowable
Load?
TMDL Workshop
-------
Example Total Phosphorus TMDL
Water Quality Standard: Maintain total phosphorus concentration at 0.05 mg/L
on an annual average basis at watershed outlet.
Watershed is all agricultural.
Pilot studies have shown that
conservation tillage will reduce
loads by 75%.
WWTP Load (Observed)
= 22,000 kg/yr = 0.7 g/sec
Upstream Load = 9500 kg/yr = 0.3 g/sec
Total Flow = 10 nnP/sec
TMDL Workshop
O?
-------
TMDL CALCULATIONS
1. Define Objective
WQS = 0.05 mg/l = 0.05 gm/m3
2. Relate Load to Water Quality
C = WvQ
Concentration = ^ Finu/
AYi i.
\D04/-*'
W = C x Q
Allowable load = Target Concentration * Flow
Nonpoint Sources = 0.3 g/sec
4. Select & Evaluate Control Alternatives
BMP (Conservative tillage) reduces loads by 75%.
5. Allocate Among Sources
policy is to achieve equal percent reduction from
~ all sources
Required reduction in total load = 50%
WLA = 0.35 g/sec
LA = 0.15 g/sec, achieved by BMP implementation
of 2/3 of the watershed
= .05 g/m3 * 10m3/sec = 0.5 g/sec
3. Estimate Sources
Point Sources = 0.7 g/sec
\ H
\.o I See
TMDL W o r k s h o p
-------
SSkpi
TMDL DEVELOPMENT
ACTIVITIES
:i¦ 1. Define quantitative objective
] b5)Oi.Lrv\jLe^'c o«- hfrls" lfr~'
-u^-V / J u tt-U'-XJr
(2. Relate load to water quality
L>) u3 ,nrv-i O d-1-^ o
3. Estimate pollution sources
4. Select/evaluate control alternatives
Kcv^ (oa^Co 4=n^f-obj
5. Allocate among sources
TMDL Workshop
-------
1. WATER QUALITY STANDARDS (WQS)
Goal of TMDL is to achieve compliance with WQS
Often the easiest part of the process, sometimes the
most difficult
Need to match response parameter with the
parameter to be controlled.
Loa ob'
Response
Parameter
L„t ^-Dissolved Oxygen
Algae
BOD, Ammonia
Nitrogen, Phosphorus
Solids
—^ Copper
Parameter to be
Controlled
-Turbidity
"W>2_
TMDL Workshop
-------
EMPIRICAL EXAMPLE
Relating Responses to Controls
Silver Creek
300 T
250
200
=>
*-
Z
,c 150
100 -
50
¦ ¦
. ¦ j
¦ -» ¦
Observed Turbidity, NTU
-t-
50
100 150
Total Suspended Solids, mg/1
200
250
Water quality standard is for turbidity.
Parameter to control is solids.
San Luis Obispo
Water quality problem = nuisance algal growth
Conduct algal assays to determine algal growth
at several different concentrations of nitrogen
and phosphorus
TMDL Workshop
LTI, Limno-Tech, Inc.
-------
Relating Response to Controls: Model Example
Dissolved Oxygen:
WWTP
BOD,
NH0
BOD
Dissolved
Oxygen
Ammonia
Eutrophication:
Nutrient
Load
[ ) \ccdc
Phosphorus
Nitrogen
Algae
THDL Workshop
-------
1/
2. Relate Load to Water Quality
Criterion
Model
Loading Capacity
Simple Model Can Be Run "In Reverse"
C = W/Q
W = C x Q
More Complex Models Must Be Run Iteratively
Model
Concentration Comply
Reduce
Load
Concentration
Load
DONE
TMDL Workshop
-------
3. ESTIMATE LOADING SOURCES
Point Sources: Relatively easy
Discharge monitoring reports
Nonpoint Sources:
Relatively difficult
Monitoring
Modeling
TMDL Workshop
-------
4. SELECT/EVALUATE ALTERNATIVES
Select Alternatives
Stakeholder input
Evaluate Alternatives
Literature search
Simple model-based estimates
SCS-provided estimates
Pilot studies
Detailed nonpoint source modeling
TMDL Workshop
-------
5. ALLOCATE LOAD
Combine policy with technical issues
Technical Issues
Determine relative contribution -
Estimate controllability
Cost benefit
Policy Issues
Public input
Intergovernmental cooperation
Enforceability of controls
TMDL Workshop
-------
l'-
Real World TMDLs
Dillon Reservoir:
Parameters: Algae, Phosphorus
Objectives: Maintain present water quality
Define Objectives
jr
v«,
Columbia Dioxin:
Parameters:
Model:
Monitor Total LoadsXJstrategy"
LA
Dioxin ^ n
^ »\s iviwui^i. 0 — W / Q ha£nrit'"r^<- rrrvOiv-v PU-u3 - A i
VW/ vx
orji^ Allocation Strategy: Pulp mills treat to level of detection
(P
o
Numeric Standard
Unallocated
OQ_ m cun
llocatio
Strategy
Loading
Capacity
WQ Model
Pulp Mill
WLA
Tualatin River:
3s'1
U
Parameters:
Objectives:
Model:
Phosphorus, Algae
Lab and field studies relating
nutrient conc. to algal growth
C = W/Q
Allocation Strategy: Tributaries at target levels
WLA = TMDL - LA
Define Objectives
WQ Model
Allocatior"
Strategy
WLA
LA
Loading
Capacity
TMDL Workshop
-------
Real World TMDLs
Saginaw Bay:
Parameters: Taste and Odor in drinking water
Objective: Correlate problems to observed
blue-green algae concentration
WQ Model: Complex multi-species
phytoplankton model
Present, Future Loads: Monitoring, Modeling
Allocation Strategy: Technology-based WLA followed
by cost-effectiveness analysis
on-point Source
Model .
Allocation
Strategy
'ater Quality
Models .
Numeric
Objective
Designated Use
Total Load
Point Source
Load
Load Response
Curve
Non-point Source
Load
Best Management
Practices
TMDL Workshop
-------
Nonpoint Source Evaluation
for TMDL Analysis
Presented by:
Paul L. Freedman, P.E.
Limno-Tech, Inc.(LTI)
Ann Arbor, Ml 48108
-------
OVERVIEW
~ Importance of Nonpoint Sources
~ Methods for Nonpoint Source
Assessment
~ Modeling Approaches
~ Model Selection
-------
Nonpoint Source Evaluation
for TMDL Analysis
Presented by:
Paul L. Freedman, P.E.
Limno-Tech, Inc.(LTI)
Ann Arbor, Ml 48108
-------
OVERVIEW
~ Importance of Nonpoint Sources
~ Methods for Nonpoint Source
Assessment
~ Modeling Approaches
~ Model Selection
-------
iu
TYPES OF NONPOINT
SOURCES
Agricultural Runoff
Soils
Pesticides/Herbicides
Animal Wastes
Urban Runoff
Residential vs. Commercial/Industrial
Combined vs. Separate Sewers
Mining
Construction
Silviculture
Land Disposal
Atmospheric Deposition
Contaminated Sediments
-------
Estimated 1986 Point and Nonpoint Phosphorus Loading to
the Great Lakes
Superior
Michigan
Huron
Erie
Ontario
St. Lawrence
Legend
~ Nonpoint Source
H Atmospheric
I Industrial
~ Municipal
Great Lakes Water Quality Board, Oct. 1989, "1989 Report on Great Lakes Water Quality",
International Joint Commission, Windsor, Ontario.
-------
Are NPS Significant?
Estuaries Lakes Rivers
¦ Non-Point Sources H Industrial Point Sources
H Combined Sewer Overflows M Other/Unknown
~ Natural Causes | Municipal Point Sources
-------
NPS CONTROL MEASURES
Agriculture
Animal waste management
Conservation tillage
Contour farming
Contour strip cropping
Cover crops
Crop rotation
Fertilizer management
Integrated pest management
Livestock exclusion
Range and pasture management
Sod-based rotation
Terraces
Construction
Distrurbed area limits
Nonvegetative soil
stabilization
Runoff detention/retention
Surface roughening
Urban
Flood storage
Porour pavements
Runoff detetion/retention
Street cleaning
Categories of Structural
Control
Storage
Treatment
Conveyance
Silviculture
Ground cover maintenance
Limiting disturbed areas
Log removal techniques
Pesticide/herbicide
Proper handling of haul roads
Removal of debris
Riparian zone management
Road and skid trial management
Mining
Block-cut or haul-back
Underdrains
Water diversion
Multi category
Buffer strips
Detection/sedimentation basins
Devices to encourage infiltration
Grassed waterway
Interception/diversion
Material ground cover
Sediment traps
Streamside management zones
Vegetative stabilization/mulching
-------
DIFFICULTIES IN
QUANTIFYING NPS
~ Event Related
- Intermittent
- Time Variable
- Event Variable
~ Diffuse
- Multiple delivery locations
0 Representing multiple sources
- Variable with location
~ Expensive
- For above reasons, many
samples needed
-------
If nonpoint sources are so difficult to
isolate, characterize, and measure, then
how do we quantify them?
-------
METHODS FOR NPS
ASSESSMENT
~ Empirical
- Measure flows, concentrations
~ Semi-empirical load estimation
- Unit area loads, export
coefficients
- Universal Soil Loss Equation
~ Model runoff
- Estimate concentration
~ Computer models
-------
METHODS FOR NPS
ASSESSMENT
~ Empirical
- Measure flows, concentrations
~ Semi-empirical load estimation
- Unit area loads, export
coefficients
- Universal Soil Loss Equation
~ Simple Models
- Simulate runoff
- Estimate concentrations
~ Computer models
-------
to
EMPIRICAL NPS METHODS
~ Empirical = Direct Measurements
~ Event
Measure hydrograph and pollutograph
~ Season/Annual
Monitor flow and concentrations
over long term
0 Compile and sum
~ Statistical
Monitor flow and concentration
over range of conditions
0 Correlate load to flow
-------
LIMITATIONS OF
EMPIRICAL METHODS
~ Limited by available data
- The amount of data required to
accurately represent a
watershed is often prohibitively
large
~ Only characterizes existing conditions
- Rainfall/hydrology specific
Can't quantify impact of future changes
0 Land Use
0 Agricultural practices
-------
SEMI-EMPIRICAL LOAD
ESTIMATES
~ Estimate loading from land parcels with
homogeneous land characteristics
~ Characterize watershed in terms of
homogeneous land parcels
~ Total load is sum of loads from
homogeneous parcels
~ Commonly used methods
- ^Unit area loads (a.k.a. export coefficients)
- ^Universal soil loss equation
~ Must also consider delivery ratio
~ Examine dissolved and particulate loads
-------
UNIT AREA LOADING
~ Mass of pollutant export per area per time
kg/ha/yr, Ib/ac/yr
~ Influencing Factors scb/torcs
Land use
Soil type
% imperviousness
~ Pollutant specific
-------
1.22
Chapter 1: Impacts of Urban Runoff
U
Table 1.5: Annual Storm Pollutant Export For Selected Values of
Impervious Cover (I) Developed from the Simple Method1
LAND2
SITE
TOTAL
TOTAL
BOD
EXTRACTABLE
USE
IMPERVIOUSNESS
PHOSPHORUS3
NITROGEN
5-day
ZINC
LEAD
RURAL
0
0.11
0.8
2.1
0.02
0.01
RESIDENTIAL
5
0.20
1.6
4.0
0.03
0.01
10
0.30
2.3
5.8
0.04
0.02
LARGE LOT
10
0.30
2.3
5.8
0.04
0.02
SINGLE
15
0.39
3.0
7.7
0.06
0.03
FAMILY
20
0.49
3.8
9.6
0.07
0.04
MEDIUM
20
0.49
3.8
9.6
0.07
0.04
DENSITY
25
0.58
4.5
11.4
0.08
0.05
SINGLE
30
0.68
5.2
13.3
0.10
0.05
FAMILY
35
0. 77
6.0
15.2
0.11
0.06
TOWNHOUSE
35
0.77
6.0
15.2
0.11
0.06
40
0.87
6.7
,17.1
0.12
0.07
45
0.97
7.4
18.9
0.14
0.07
50
1.06
8.2
20.8
0.15
0.08
GARDEN
50
1.06
8.2
20.8
0.15
0.08
APARTMENT
55
1.16
8.4
22. 7
0.16
0.09
60
1.25
9.6
24.6
0.18
0.09
HIGH RISE,
60
1.25
9.6
24.6
0.18
0.09
LIGHT
65
1.35
10.4
26.4
0.19
.0.10
COMMERICAL/
70
1.44
11.1
28.3
0.21
0.10
INDUSTRIAL
75
1.54
11.8
30.2
0.22
0.11
80
1.63
12.6
32.0
0.23
0.11
HEAVY
80
1.63
12.6
32.0
0.23
0. 11
COMMERCIAL,
85
1.73
13.3
33.9
0.25
0.12
SHOPPING
90
1.82
14.0
35 .8
0.26
0.13
CENTER
95
1.92
14.8
37.7
0.27
0.13
100
2.00
15.4
39 .2
0.28
0.14
1 P=40 inches, Pj=0.9, Rv=0.05+0.009(I), ,C=suburban values, A=1 acre.
2 Rural Residential: 0.25-0.50 Dwelling Units (DU)/acre
Large Lot Single Family: 1.0-1.5 DUs/acre
Medium Density Single Family: 2-10 DUs/acre
Townhouse and Garden Apartment: 10-20 DUs/acre
3 These values are for NEW DEVELOPMENT SITES ONLY. For older urban
areas, central business districts, sites with highways, or areas out-
side of the Middle Atlantic region, use a more appropriate "C" value
in Equation 1.1 (see Table 1.1).
-------
Comparative Pollutant Removal Of Urban BMP Designs
BMP/design
EXTENDED 0ETENT10N PONO
OESIGN 1
moderate
OESIGN 2
KEY:
OESIGN 3
HIGH
0 TO 20* REMOVAL
20 TO 40% REMOVAL
OESIGN 4
MODERATE
40 TO 00% REMOVAL
OESIGN S
MOOERATE
00 TO 60% REMOVAL
OESIGN e
HIGH
60 TO 100% REMOVAL
INFILTRATION TRENCH
INSUFFICIENT
KNOWLEDGE
OESIGN 7
OESIGN 8
HIGH
OESIGN 9
HIGH
NFILTRATION BASIN
OESIGN 7
MODERATE
OESIGN 8
HIGH
OESIGN 9
HIGH
POROUS PAVEMENT
MOOERATE
DESIGN 7
OESIGN 8
HIGH
DESIGN 9
HIGH
WATER QUALITY INLET
OESIGN 10
LOW
FILTER strip
OESIGN 11
LOW
OESIGN 12
MOOERATE
GRASSED SWALE
OESIGN 1 3
LOW
OESIGN 14
LOW
First-flush runoff volume detained for 6-12 hours.
Runoff volume produced by 1.0 inch, detained 24 hours.
As in Design 2, but wich shallow oarsn in bottom stage.
Permanent pool equal co 0.5 inch storage per uopervious acre.
Permanent pool equal to 2.*5 (Vr); wnere Vr=roean storm runoff.
Permanent pool equal co 4.0 (Vr), approx. 2 weeks retention.
Facility exfiltrates first-flush; 0 5 men runoff/imper. acre
Facility exfiltrates one inch runoff volume per imper. acre.
Facility exfiltrates all runoff, up to tne 2 year aesign storm.
400 cubic feet wet storage per impervious acre.
20 foot vide turf strip.
100 foot wide forested strip, with level spreader.
High slope swales, with no check dams
Low gradient swales with check daas.
Design
Design
2
Design
3
Design
4
Design
3
Lasign
0
Design
7
Design
a
Design
9
Design
10
Design
11
Design
12
Design
13
Design
14
(Controlling Urban Runoff; MWCOG 1987)
-------
Comparative Pollutant Removal Of Urban BMP Designs
BMP/design
EXTENDED DETENTION POND
DESIGN 1
MODERATE
DESIGN 2
MODERATE
KEY:
DESIGN 3
HIGH
0 TO 20% REMOVAL
WET POND
20 TO 40% REMOVAL
DESIGN 4
MODERATE
40 TO 00% REMOVAL
DESIGN S
MODERATE
60 TO S0% REMOVAL
DESIGN 6
HIGH
00 TO 100% REMOVAL
INFILTRATION TRENCH
INSUFFICIENT
KNOWLEDGE
DESIGN 7
MODERATE
DESIGN 8
HIGH
DESIGN 9
HIGH
INFILTRATION BASIN
DESIGN 7
MODERATE
DESIGN 8
HIGH
DESIGN B
HIGH
-------
UNIVERSAL SOIL LOSS
EQUATION
X = (E) K (LS) C (P)
X = soil loss (mass/area)
E = rainfall erosivity °
K = soil erodibility
LS = topographic factor —i \ op*-
C = cover factor
P = management practice factor
~ Can be applied on an annual or event basis
~ Tables are available to define values of
each factor based upon site-specific
characteristics
/cuwa-b^ "bcLCtU
-------
Average Annual Erosivity Indices (Eggi ish Units.).
For Eastern U.S. (Wischmeier and Smith, 1978)
-------
Average Annual Erosivity Indices (English Units)
For Western U.S. (Wischmeier and Smith, 1978)
-------
Monthly distribution of erosive rainfall as a percentage of total rain<
fail. (Reprinted from references .)
-------
SOIL ERODIBILITY,(<
(Stewart et al, 1975)
Texture
Organic Matter
0.5%
2%
4X
Sand
0.05
0.03
0.02
Fine sand
0.16
0.14
0.14
Very fine sand
0.42
0.36
0.28
Loamy sand
0.12
0.10
0.08
Loamy fine sand
0.24
0.20
0.16
Loamy very fine sand
0.44
0.38
0.30
Sandy loam
0.27
0.24
0.19
Fine sandy loam
0.35
0.30
0.24
Very fine sandy loam
0.47
0.41
0.33
Loam
0.38
0.34
0.29
Silt loam
0.48
0.42
0.33
Silt
0.60
0.52
0.42
Sandy clay loam
0.27
0.25
0.21
CI ay 1 oam
0.28
0.25
0.21
Silty clay 1 oam
0.37
0.32
0.26
Sandy clay
0.14
0.13
0.12
Silty clay
0.25
0.23
0.19
CI ay
0.13-0.29
nVACiLt IcuV/drd
-------
-------
UTAH COUNTY AREA. IDAHO
">58 SOIL SURVEY
TABLE 16 AHD CHEMICAL PROPERTIES OF SOILS
[The symbol < Beans leas than; > Beans nore than. Entries under "Erosion factors—apply to the entire
profile. Entries under "Orjanlc natter* apply only to the surface layer. Absence of an entry indicates
that data were not available or were not estimated!
Soil nut and
aap syabol
epcnlciay <2nnl ?eroeattility
Available
water capacity
Soil
eactlon
Shrink-swell
potential
irosion j
factor:
Agatha
2* .
Aquic
Xerofluvents
Athena
3* :
Athena-
?alouse-
31uesprin-
FlyOow-
6»:
Slueaprln-
Xeuterville-
Cruoarine
8»:
Driscoll-
Larlein-
farber-
Hlnaloosa-
10-
larfleld
n
,-ct
in/ nr
m/ in
-7
-18
-53
35
15-22
20-27
27-35
0.6—2.0
0.6-2.0
0-6-2.0
0-. 14-0.19
0.10-0.16
Q.10-0.14
0-17
-50
O-oO
15-22
18-25
15-20
0.6-2.0
0.6-2.0
0.6-2.0
0.19-0.21
0.19-0.21
0.15-0.21
0-17
7-50
0-60
15-22
18-25
15-20
0.6-2.0
0.6-2.0
0.6-2.0
0 .19-0.21
0.19-0.21
0.19-0.21
0-15
15-60
18-24
20-30
0.6-2.0
0.6-2.0
0.19-0.21
0.19-0.21
0-11
1-au
24
18-24
27-32
0.6-2.0
0.2-0.6
0.16-0.19
0.12-0.16
0—4
4
10-15
0.6-2.0
0.06-0.08
0-11
1-24
24
18-24
27-32
0.6-2.0
0.2-0.5
0.16-0.19
0.12-0.16
0-13
3-44
44-60
18-25
27-35
20-30
0.6-2.3
0-2-0.6
0 - 2—0.5
0. 12-0.14
0.06-0.10
0.06-0.08
0-9
9-46
46-60
15-20
10-18
5-10
0.6-2.0
0.6-2.0
2-0-6.0
0.18-0.21
0.11-0.18
0.04-0.10
0-33
3-60
20-25
35-4 5
0.6-2.0
0.06-0.2
0.19-0.21
0.15-0.20
0-21
21-60
15-24
24-30
0.6-2.0
0.2-0.6
0.19-0.21
0.19-0.21
0-1
1-16
6-44
44-60
15-22
15-22
15-22
15-22
0.6-2.0
0.6-2.0
0.6-2.0
0.6-2.0
0.16-0.21
0.12-0.18
0.10-0.13
0.05-0.10
0-6
6-22
22-6
15-22
15-22
15-22
0.6-2.0
0.6-2.. 0
0.6-2.0
0.14-0.18
0.12-0.16
0. 12-0. 16
0-8
a-z
22-0
22-27
35-55
25-35
0.2-0.6
0.06-0.2
0.2-0.6
0.17-0.20
0.14-0.16
0.18-0.21
on
.1-7.3
.1-6.5
.6-6.5
,ov-
.1-7.3
.6-7.3
.5-8.a
.ou-
ow-
,oy-
.1—7.3
.3-
.3-
.6-
. l-
,i-
i
7 .8
3.#
7.3
7.S
¦7.3
•7.3
.ou-
.ou-
Hoderate-
,.6-7.3
,ou-
. 1-
6.1-
•7.3
¦7.3
Low
Moderate—
6.1-7.3
6.1-7.3
6.1-7.3
5.6-6.5
5.6-6o
5.6-6.0
5.6-7.3
5.6-7 .3
5.6-7.3
5.0-7.3
6.1-7.3
6.1-7.3
5 - 6-6.5
5.6-6.5
5.6-6.5
5.1-6.5
5.1-6.5
6.1-7.3
6.6-7 .8
6.6-3.4
.ow-
,ow-
.ou-
.ow-
Low-
Lou-
Low—
High-
Lo«-
Moderate-
Lovi-
Low-
Low-
Low-
Lou-
Lou-
Lou-
Hlgtl
Hoderate-
-10.2a;
•10.37!
¦10.37',
-10.32!
-10. a 9 i
-:o.55!
BV
ioderace
10.32!
10.591
10.35!
1.-32!
!0.53:
-10.28!
-10.2S;
-!0.28!
-10.281
-!0.281
-10.32!
¦JO.32!
•10.32!
I 1
-1Q -« 31
-10.24!
-10.201
I
r 1
-:0.32s'
-10.371
I I
•I0.32!
• 10.113!
-10.32!
-10.371
-10.28!
• 10.241
-io.32!
- i 0 . 3TI
-10.371
-;o.32'!
-{0.281
-50.32',
See footnote at end of table.
-------
60
°o
20 -I
I0H
°o.
°°
°o
¦°o
0.6J
0.3 H
02. -i
600 1000
300
100
60
30
10
SLOPE LENGTH, meters
Length-slope factor (LS) for different slopes. (Taken from references )
LS = L1/2 (0.00138 + 0.00974S + 0.00138S2)
-------
n
TABLE 5-3. Values oiC jor Cropland, Pasture,
and WoocHand.®
Land Cover or Land Use C
Continuous Tallow tilled up and down slope 1.0
Shortly after seeding or harvesting6 0.3-0.8
For crops during main pail of growing season
Corn0 0.1-0.3
Wheat0 0.05-0.15
Cotton 0.4
Soybeans0 0.2-0.3
Meadow0 0.01-0.02
For permanent pasture, idle land, unmanaged woodland
Ground cover 95-100%
As grass
As weeds
Ground cover 80%
As grass
As weeds
Ground cover 60%
As grass
As weeds
For managed woodland
Tree canopy of 75-100%
40-75%
20-40%
0.003
0.01
0.01
0.04
0.04
0.09
0.001
0.002-0.004
0.003-0.01
'Adapted from references 3, 7, and 10.
Depending on root and residue density.
""Depending on yield.
iVVi
TABLE 5-6. Values of P for Agricultural Land."
Strip Cropping and Terracing
Slope (%)
Contouring
Alternate Meadows
~osegrown Crops
1.1-2.0
0.6
0.30
0.45
2.1-7.0
0.5
0.25
0.40
7.1-12.0
0.6
0.30
0.45
12.1-18.0
0.8
0.40
0.60
18.1-24.0
0.9
0.45
0.70
>24.0 1.0
* Adapted from reference 1.
Novotny & Cheslers, 198:
-------
SEDIMENT DELIVERY
R ATIQ ^
Qntom
~ Unit area load, USLE estimate amount of
pollutant exported from the land surface
~ They do not estimate how much pollutant is
ultimately delivered to the receiving water of
concern.
~ Ratio of sediment eroded:sediment
delivered is called the delivery ratio
~ Factors affecting the delivery ratio
- Watershed size
Relief
Bifurcation
^5* btfl'tohinq of sVaai
-------
g 0.40
£ 0.30
0.20
Ui
uj 0.08
0.06
H-
S 0.04
cn 0.02
10
100
1000
ORAINAGE AREA (km2)
Sediment Delivery Ratio As A Function Of
Watershed Drainage Area (Vanoni, 1975)
^ (X\_2A- ^
-------
PARTICLE-BOUND
POLLUTANTS
~ Many watershed sources of pollutant occur
predominantly in the particulate phase,
sorbed onto soil particles
~ Pollutant loading rates can be directly
estimated from results of USLE
UlniV. S«> I (-oss
Xi = Pi x Xs
X| = loading of pollutant I
Pi = potency factor for the pollutant
xs = loading of solids
~ Potency factors available from local soil
agency
-------
Basic Modeling Theory
trO^eO instead
Loadioii
Quality
Q x C = W
Flow x Concentration = Load
-------
SIMPLE METHOD
Q x C = W
Flow x Concentration = Load
~ Flow (Q)
- Can be monitored or estimated from:
0 Rational method
0 SCS Curve Number approach
~ Concentration (C)
Observed
BPJ from other sites
-------
RATIONAL METHOD
Q = CIA
~ Q = Runoff flow (L3/T)
~ C = Runoff coefficient
- Basin specific
- Sometime referred to as Rv,
- For rural lands C = 1.0 - Zrf
i - a-3'mfall intensity (L/T)
Lp-f^vCcK r^Ufv-J
-------
Urban Areas
Runoff Coefficients.3
Runoff
Description of Area Coefficient
Flat, residential, with about 30% of area
impervious 0.40
Moderately steep, residential, with about 50%
of area impervious 0.65
Moderately steep, built-up, with about 70%
of area impervious 0.80
Table from Homer and Ftynt-Transactions ASCE 1936.
Deductions from unity to obtain runoff coefficients for
agricultural areas
Type of Area Value of f
Topography
Flat land, with average slopes of 0.02-0.06% 0.30
Rolling land, with average slopes of 0.3-0.4% 0.20
Hilly land, with average slopes of 3-5% 0.10
Soil
Tight, impervious clay 0.10
Medium combination of clay and loam 0.20
Open, sandy loam 0.40
Cover
Cultivated lands 0.10
Woodland 0.20
Table from Bernard-Transactions ASCE 1935.
aReprinted from "Handbook on the Principles of Hydrology" by D.M
Gray18 by permission of the National Research Council of Canada.
^The magnitude of the runoff coefficient, Rv, is obtained by adding values
of r1 for each of the three factors: topography, soil, and cover, and by
subtracting the sum from unity.
Novotny & Chesters, 1981
-------
x SCS CURVE NUMBER
^ APPROACH
^ (P-0.2S)2 r „
Q = - — forP < 0.2S
(P+0.8S)
Q = runoff (cm)
P = precipitation (cm)
S = water retention parameter
= f(soils, management, antecedent
moisture)
\\(A^ \\ i//tv.v\01..U \)cvyiA ov)
V] vJ 1
-------
HYDROLOGY: SOLUTION OF RUNOFF EQUATION Q' t£7§f-lJ*
P> 0 lo 12 inchet
0-0 lo B Inchet
Rainfall |P|
RUNOFf (01
IP-I.I'
0- jzyis *"h p* l,: Si ,0'F:
•nd r* p-i0-o
com L* O.t 9. •« lhal
o. K-o-«»r
pfo.e
In 111 oI
obitfoetion I#
Infiltration
t| i-ii-n
SCS Curve Number Runoff Equation (1 in = 2.5'Icm)
/V
-------
Table B-1.
Descriptions of Soil Hydrologic Groups (Soil Conservation Service, 1986)
. Soil
Hydrologic Group Description
A Low runoff potential and high infiltration rates even when thoroughly wetted. Chiefly
deep, well to excessively drained sands or gravels. High rate of water transmission
(> 0.75 cm/hr).
B Moderate infiltration rates when thoroughly wetted. Chiefly moderately deep to deep,
moderately well to well drained soils with moderately fine to moderately coarse
textures. Moderate rate of water transmission (0.40-0.75 cm/hr).
C Low infiltration rates when thoroughly wetted. Chiefly soils with a layer that impedes
downward movement of water, or soils with moderately fine to fine texture. Low rate
of water transmission (0.15-0.40 cm/hr).
D High runoff potential. Very low infiltration rates when thoroughly wetted. Chiefly clay
soils with a high swelling potential, soils with a permanent high water table, soils
with a ciaypan or clay layer at or near the surface, or shallow soils over nearly
impervious material. Very low rate of water transmission (0-0.15 cm/hr).
Disturbed Soils (Major altering of soil profile by construction, development):
A Sand, loamy sand, sandy loam.
B Silt loam, loam
C Sandy clay loam
D Clay loam, silty clay loam, sandy clay, silty clay, clay.
-------
Table B-2. Runoff Curve Numbers (Antecedent Moisture Condition II) for Cultivated Agricultural
Land (Soil Conservation Service. 1986).
Land Use/Cover
Hydrologic Soil Hydrologic Group
Condition A B C D
Fallow Bare Soil
Crop residue cover (CR)
Row Crops
Small SR
Grains
Close- SR
seeded or
broadcast
legumes or
rotation
meadow
Straight row (SR)
SR + CR
Contoured (C)
C + CR
Contoured & terraced (C&T)
C&T + CR
SR * CR
C
C + CR
C&T
C&T + CR
C
C&T
77
86
91
94
Poor2/
76
85
SO
93
Good
74
83
83
90
Poor
72
81
88
91
Good
67
78
85
89
Poor
71
80
87
90
Good
64
75
82
85
Poor
70
79
84
88
Good
65
75
82
86
Poor
69
78
83
87
Good
64
74
81
85
Poor
66
74
80
82
Good
62
71
78
81
Poor
65
73
79
81
Good
61
70
77
80
Poor
65
76
84
88
Good
63
75
83
87
Poor
64
75
83
86
Good
60
72
80
84
Poor
63
74
82
85
Good
61
73
81
84
Poor
62
73
81
84
Good
60
72
80
83
Poor
61
72
79
82
Good
59
70
78
81
Poor
60
71
78
81
Good
58
69
77
80
Poor
66
77
85
89
Good
58
72
81
85
Poor
64
75
83
85
Good
55
69
78
83
Poor
63
73
80
83
Good
51
67
76
80
combination of factors that
affect
infiltration
a u. vcyeuiuve areas, amount or year-round cover, (c) amount
of dose-seeded legumes in rotations, (d) percent of residue cover on the land surface (good ;»
20%), and (e) degree of surface roughness.
-------
Runoff Curve Numbers (Antecedent Moisture Condition II) for other Rural Land (Soil
Conservation Service, 1986).
Land Use/Cover
Hydrologic
Condition
Soil Hyarologic Group
A B C
D
Pasture, grassland or range
Poor3/
68
79
86
89
- continuous forage for grazing
Fair
49
69
79
84
Good
39
61
74
80
Meadow - continuous grass, protected
from grazing, generally mowed for hay
-
30
58
71
78
Brush - brush/weeds/grass mixture
Poor'3/
48
67
77
83
with brush the major element
Fair
35
56
70
77
Good
30
48
65
73
Woods/grass combination
Poor
57
73
82
86
(orchard or tree farm)0/
Fair
43
65
76
82
Good
32
58
72
79
Woods
Poor/d
45
66
77
83
Fair
36
60
73
79
Good
30
55
70
77
Farmsteads - buildings, lanes,
driveways and surrounding lots
-
59
74
82
86
a/ Poor: < 50% ground cover or heavily grazed with no mulch; Fair 50 to 75% ground cover and
not heavily grazed; Good: > 75% ground cover and lightly or only occasionally grazed.
k/ Poor. < 50% ground cover, Fair. 50 to 75% ground cover; Good: > 75% ground cover.
c/ Estimated as 50% woods. 50% pasture.
Poor forest litter, small trees and brush are destroyed by heavy grazing or regular burning; Fair:
woods are grazed but not burned and some forest litter covers the soil: Good: Woods are protected
from grazing and litter and brush adequately cover the soil.
-------
J-T
ANTECEDENT MOISTURE LIMITS FOR CURVE NUMBER SELECTION
(Ogrosky and Mockus, 1964)
Antecedent
Moisture Condition
5-Day Antecedent
Precipitation
(cm)
Dormant
Season*
Growi ng
Season
I
<1.3
<3.6
II
1.3-2.8
3.6-5.3
III
>2.8
>5.3
*During snowmelt, condition III is always assumed
regardless of antecedent precipitation.
-------
M~\
(A)
.(3)
9.0
I ,/'
9.0
\0 yv
< O- 's'
O.* '
(C)
(D)
Mean Annual Row Crop Runoff In Inches
For Selected Curve Numbers. A; CN2=67,
B: CN2=78; C: CN2=85; D: CN2=89. (1 in
= 2.54cm) (Stewart Et Al, 1976)
-------
SIMPLE METHOD
Q x C = W
Flow x Concentration = Load
~ Flow (Q)
- Can be monitored or estimated from:
0 Rational method
0 SCS Curve Number approach
~ Concentration (C)
Observed
BPJ from other sites
-------
! rv. CK
\W--;
Urban 'C' Values For Use With the Simple Method (mg/1)
NEW
OLDER
CENTRAL
NATIONAL
HARDWOOD
NATIONAL
SUBURBAN
URBAN
BUSINESS
NURP
FOREST
URBAN
NURP SITES
AREAS
DISTRICT
STUDY
(Northern
HIGHWAY
POLLUTANT
(Wash.,DC)
(Baltimore)
(Wash.,DC)
AVERAGE
Virginia)
RUNOFF
PHOSPHORUS
Total
0.26
1.08
-
0.46
0.15
-
Ortho
0.12
0.26
1.01
-
0.02
-
Soluble
0.16
-
-
0.16
0.04
0.59
Organic
0.10
0.82
-
0.13
0.11
NITROGEN
Total
2.00
13.6
2.17
3.31
0.78
-
Nitrate
0.48
8.9
0.84
0.96
0.17
-
Ammonia
0.26
1.1
-
-
0.07
-
Organic
1.25
-
-
-
0.54
-
TKN
1.51
7.2
1.49
2.35
0.61
2.72
COD
35.6
163.0
-
90.8
>40.0
124.0
BOD (5-day) 5.1
-
36.0
11.9
-
-
METALS
Zinc
0.037
0.397
0.250
0.176
-
0.380
Lead
0.018
0.389
0.370
0.180
-
0.550
Copper
•
LO
o
»—1
o
•
0.047
-
-
(Controlling Urban Runoff; MWCOG 1987)
-------
Kj •-! i L
NURP MEDIAN SITE EMC's
(NURP, 1983)
Values are median (mean)
Site San Francisco Area. CA Bellevue. WA
Land Use
Urban Open
and Nonurban
Mixed
Residential (2 sites)
TSS (mg/1)
551
(718)
171
(283)
100-101
(118-127)
BOD (mg/1)
COD (mg/1)
102
(111)
80
(931)
32-42
(44-48)
TP(ug/l)
455
(590)
374
(418)
184-204
(239-264)
Sol. P (ug/1)
91
(145)
120
(169)
TKN (ug/1)
3159
(3674)
1775
(2220)
852-857
(1007-1056)
N03-N02 (ug/1)
1383
(1542)
1044
(1111)
Tot. Cu (ug/1)
55
(58)
65
(98)
21
(22)
Tot. Pb (ug/1)
159
(214)
351
(495)
136-159
(152-192)
Tot. Zn (ug/1)
160
(190)
231
(303)
107-114
(120-124)
-------
Land Use
Nitrogen Phosphorus
( (mg//) )
tt
Fallow3/ 2.5 0.10
Corn3' 2.9 0.26
Small grains3' 1.3 0.20
Hay3/ 2.3 0.15
Pasture3' 3.0 0.25
Barn yards / 2S.3 £.10
Snowmelt runoff from manured landc<^
Com 12.2 1.S0
Small grains 25.0 £.00
Hay 36.0 8.70
a^Dombush et al. (1974)
^Edwards et al. (1972)
c /
' Gflbertson et al. (1979); manure left on soil surface.
?<>
Table 6-15.
Dissolved Nutrients in Agricultural Runoff.
Watershed
Concentrations (mg/0
Type
Eastern U.S. Central U.S. Western U.S.
N'rtroaen3/:
a 90% Forest
0.19
0.06
0.07
s 75% Forest
0.23
0.10
0.07
2: 50% Forest
0.34
0.25
0.18
i 50% Agriculture
1.08
0.65
0.83
>75% Agriculture
1.32
o.so
1.70
s 90% Agriculture
5.04
0.77
0.71
PhosDhorus^/:
s 90% Forest
0.006
0.009
0.012
a 75% Forest
0.007
0.012
0.015
^ 50% Forest
0.013
0.015
0.015
2: 50% Agriculture
0.029
0.055
0.083
i 75% Agriculture
0.052
0.067
0.069
a 90% Agriculture
0.067
0.085
0.104
^Measured as totaJ inorganic nitrogen.
^/Measured as total orthopnosphorus
Table B-16. Mean Dissolved Nutrients Measured in Streamflow by National Eutrophication
Survey (Omernik, 1977).
40
$WLF MANUAL
-------
•? -
, /
EMC Mean Values for Pollutant Load Estimates (EPA, 1983)
Site Mean EMC
Constituent
Median urban site
90th percentile urban site
TSS (mg/L)
141
to
224
424
to 671
BOD, (mg/L)
10
to
13
17
to 21
COD (mg/L)
73
to
92
157
to 198
Tot. P (mg/L)
0.37
to
0.47
0.78
to 0.99
Sol. P (mg/L)
0.13
to
0.17
0.23
to 0.30
TKN (mg/L)
1.68
to
2.12
3.69
to 4.67
N02+3:N (mg/L)
0.76
to
0.96
1.96
to 2.47
Tot. Cu (fxg/L)
38
to
48
104
to 132
Tot.Pb (ixg/L)
161
to
204
391
to 495
Tot. Zn (jxg/L)
179
to
226
559
to 707
From: Novotny, V., Jan. 1992, "Unit Pollutant Loads", Water Environment &.
Technology, Vol. 4, No. 1, pp. 40-43.
EPA, 1983, "Results of the Nationwide Urban Runoff Program, Volume 1,
Final Report", U.S. Environmental Protection Agency Water Planning
Division, Washington, D.C.
-------
METHODS FOR NPS
ASSESSMENT
~ Empirical
- Measure flows, concentrations
~ Semi-empirical load estimation
- Unit area loads, export
coefficients
- Universal Soil Loss Equation
~ Simple Models
- Simulate runoff
- Estimate concentrations
~ Computer models
-------
SIMPLE & EMPIRICAL
METHODS SUMMARY
~ Advantages
Applicable to most watersheds
Suitable for most pollutants
Easy to use
Good for relative comparisons
~ Disadvantages
Limited accuracy
Limited applicability for future projections
Not a good absolute predictor
No information on variability
-------
COMPUTER MODELS
~ Several models are available to predict
watershed hydrology and loads
~ Wide range of models available
Varying complexity
- Varying applicability
~ Don't use these models
Unless you have a good understanding
of the theory presented up to now
-------
WATERSHED MODELING
THEORY
~ Simulation of water movement
~ Simulation of dissolved pollutants
~ Simulation of solids
- Particle-bound pollutants
-------
Rain (Snow Melt)
Pervious Areas
vaporation
I
Impervious Areas
Interception
Storage
fE vaporation
I
I
Depression
Storage
Depression
Storage
Erosion
Evaporation
Sewers
Runoff
Infiltration
~ Surface f 0
Runoff ^ n
k
<
£vapo-
Upper Zone
Flow and
Storage
4 1 !~
- .Interflow* . •
i
transpiration
* i *
• - ,•
• * i * i *
>
i
1
.'
« "i i
• • •
i
» »
Groundwater
Flow and
Storage
• • •
• » • « • «
•
* > n
1
• 1 » 1 i 1
i < i
•
i
1
Geological Water Loss
Stream Flow
and
Storage
TMDL Workshop
-------
HYDROLOGIC MODEL
COMPONENTS
~ Interception storage
- Plant types
- % coverage
~ Depression storage -poVhoU^A.
~ Infiltration
~ Overland flow
- Slope
- Roughness
- Channel Routing
-------
LOADING MODEL
COMPONENTS
~ Pollutant Build-Up
- Land use
- Management practices
0 e.g. street cleaning
- Atmospheric deposition
~ Erosion of particulate material
- Rainfall impact
- Overland flow
-------
Agricultural NPS Models
Rainfall
Driving Force
Interception
Infiltration
Surface Detention
Surface Retention
I _ Water Losses
if
$
o
t:
£
c
«5
c
CO
"O
-------
Urban NPS Modeling
Pollutant
Build Up
Rainfall
Water Losses
Hydrological
Runoff
Pollutant
Wash-Off
p.^S' W "5.WW.W
Sewer
Routing
1
Storage
Treatment
LOADS
h:\ltimk\mk01\urban. vsd
-------
AVAILABLE MODELS
~ Simple models
- Application of simple theory presented
earlier
- Hand calculate or spreadsheet
~ Mid-range models
- GWLF, AGNPS, SLAMM, NPSMAP
~ Complex models
- SWMM, HSPF, SWRRB, ANSWERS
~ Compendium of Watershed Scale
Models for TMDL Development
(EPA, 1992)
- EPA-841R-94-002
-------
MODEL INPUT REQUIREMENTS
~ Watershed
Size
Homogeneous subareas
Slope
%impervious
Drainage routing
Land use
~ Rural
Crop type
Crop stage
Soil type
- Tillage practices
Fertilization practices
~ External
Precipitation
Evaporation
~ Urban
Pollutant build-up rates
Curb density
Sewer characteristics
-------
MODEL SELECTION
~ System Characteristics
- Urban, rural, or mixed use?
Pollutant of concern
- Time scale of pattern (event or annual)
~ Management Objectives
- Planning, regulations
~ Project Constraints
- Available data
- Time, money
User skills/resources
~ Start simple; add complexity only as
necessary!
-------
DRAFT June 8, 1993
Table 3-2. Runoff Models
Model
Other
Uses
Main
Rcf.
1 —
Review
Land
Use
Consti-
tuents
Load
Generation
Sediment
Erosion
Time Step
Routing -
Transfor-
mation
Agency
EPA Statistical
NR
1,2
a,b,c
U,R
General
Loading
Function
USLE/
MUSLE
Annual,
Event Ave.
no
EPA
USGS Regression
NR
3
a,b
U
N,0,M,C
Loading -
Regression
N/A
Annual,
Event Ave.
no
USGS
FHWA
NR, RQ
2
a,b
High-
way
"n,c,m
Loading -
Median
Cone.
N/A
Annual,
Event Ave.
no
FHWA
Watershed
8
a
U,R
General
Loading
Function
USLE
Annual
no
USGS
GWLF
NR
4
a
U,R
N,S
Loading
Function
MUSLE
Continuous
Monthly
no
Univ.
AGNPS
NR
5
a,b
R(Ag)
N,S
Potency
Factors
MUSLE
Continuous
Hourly
no
USDA/
ARS
STORM-RWQM
NR,RF,
RQ
6
a,b,c,d
U
N,0,M#S
Buildup-
Washoff
USLE
Continuous
Hourly
no
HEC
ANSWERS
NR
7,11
a,b
R(Ag)
N,S
Potency
Factors
Detach-
ment
Event
yes
Univ.
DR3M-QUAL
NR
13
a,b,c
U
N,S,C,M
Buildup-
Washoff
MUSLE
Continuous
Subhourly
no
USGS
SWRRBWQ
NR,RF,
RQ
9
a,b
R
S,N,C,NC
Buildup-
Washoff
MUSLE
Continuous
Daily
yes
USDA/
ARS
EPA TGM Wet Weather TMDLs
-------
DRAFT
June 8, 1993
Table 3-2 (continued)
SWMM
NR
10
a,b,c,d
U
General
Buildup-
Washoff
MUSLE
Continuous
Subhourly
yes
EPA/
CEAM
HSPF
NR,RF,
RQ
12
a,b,c,d
U,R
General
Loading-
Washoff
Detach-
ment
Continuous
Subhourly
yes
EPA/
CEAM
CREAMS
NR
15
a,d
R
(field
scale)
S>1,C,NC
Potency
Factors
Continuous
Dally
yes
USDA/A
RS
Auto Q-
ILLUDAS
MR
14
a
U
s,n,c,
NC,0
Buildup-
Washoff
Continuous
Event
no
Illinois
sws
Watershed
Management
Model
RQ
16
a
U,R .
N,M
Loading
Function
NA
- Annual
no
Florida
DER
Key to References
1. Hydroscience, 1979
2. Driscoll et al., 1990
3. Driver and Tasker, 1988
4. Haith et alv 1992
5. Young et al. 1986
6. HEC 1977a
7. Beasley & Huggins, 1981
8. Walker et al., 1989
9. Arnold et al., 1991
10. Huber & Dickinson, 1988
U. Dlllaha et al., 1988
12. johanson et al., 1984
13. Alley & Smith, 1982b
14. Terstiiep et al., 1990
15. Knleel, 1980
16. CDM, 1992
Key to Reviews
a. U.S. EPA, 1992
b. Donigian It Huber, 1991
c. WPCF, 1989
d. McKeon & Segna, 1987
EPA TGM Wet Weather TWDLs
-------
DRAFT June 8, 1993
Table 3-1 (continued)
HSPF
NQ,RF,
RQ
12
a,b,c,d
U,R
Water Balance,
Hydrologic
Routing
Continuous
Subhourly
EPi4 / CEAM
Auto Q-'LLUDAS
NQ
13
a
U
Water Balance
Continuous
Event
Illinois State
Water Survey
CREAMS
NQ
14
a,d
R (field
scale)
Water Balance
Continuous
Daily
USDA/ARS
TR-20
RF
15
R
Curve Number
Event, Sub-
event
SCS
HEC-1
RF
16
R
Multiple (UH to
Kinematic)
Event, Sub-
Ev- .t
HEC
TR-55
17
U
Curve Number
Event
SCS
Key to Kelerences
1. Hydroscience, 1979
2. Driscoll et al., 1990
3. Driver and Tasker, 1988
4. Haith et al., 1992
5. Young et al. 1986
6. HEC, 1977a
7. Beasley & Huggins, 1981
8. Alley and Smith, 1982a
9. Arnold et al., 1991
10. Huber & Dickinson, 1988
11. Roesner et al., 1988
12. Johanson et al., 1984
13. Terstriep et al., 1990
14. Knisel, 1980
15. SCS, 1973
16. HEC, 1985
17. SCS, 1986
Key to Reviews
a. U.S. EPA, 1992
b. Donigian & Huber, 1991
c. WPCF, 1989
d. McKeon & Segna, 1987
EPA TGM Wet Weather TMDLs
-------
DRAFT
June 8, 1993
Table 3-1. Runoff Qu^nt)ty Models
Model
Other
Uses
M..,n
Ref.
Reviews
Land Use
Simulation
Type
Time Step
Agency
EPA Statistical
NQ
1,2
a,b,c
U,R
Runoff Coeff.
Annual,
Event Ave.
El A
USGS Regression
NQ
3
a,b
U,R
Regression
Annual,
Event Ave.
USGS
FHWA
NQ, RQ
2
a,b
Highway
Runoff Coeff.
Annual,
Event Ave.
FHWA
GWLF
NQ
4
a
U,R
Curve Number
Continuous
Monthly
Cornell Univ.
AGNPS
NQ,RF,
RQ
5
a,b
R(Ag)
Curve Number
Continuous
Hourly
USD A/
ARS
STORM-RWQM
NQ,RF,
RQ
6
a,b,c,d
U
Runoff Coeff./
Curve #
Continuous
Hourly
HEC
ANSWERS
NQ
7
a,b
R
Water Balance
Event
Univ.
DR3M
NQ
8
a,b,c
U
Kinematic
Wave
Continuous
Subhourly
USGS
SWRRBWQ
NQ,RF,
RQ
9
a,b
R
Curve #/ Water
Balance
Continuous
Daily
USD A/
ARS
SWMM
NQ
10,11
a,b,c,d
U
Kinematic &
Dynamic Wave
Continuous
Subhourly
EPA/ CEAM
EPA TGM Wet Weather TMDLs
-------
-Q
O
*
"53
CC
Complexity
Relation Between Model Complexity
and Reliability
LTI, Limno-Tech, Inc.
-------
Defining Model Complexity
Based on Data and Resources Available
Data/Resources
-------
NPS SOURCE MODELING
SELECTED REFERENCES
Handbook of Nonpoint Pollution, Novotny & Chesters, Van
Nostrand Reinhold Co., New York, NY, 1981.
Modeling of Nonpoint Source Water Quality in Urban and
Nonurban Area. Donigian & Heber, U.S. Environmental
Research Laboratory, Athens, GA, 1991.
Control and Treatment of Combined Sewer Overflows. Moffa
et al., Van Nostrand Reinhold Co., New York, NY, 1990.
Combined Sewer Overflows Pollution Abatement. Manual of
Practice FD-17, WPCF, Alexandria, Va, 1989.
-------
£/¦ /
GENERAL REFERENCES
Novotny, V., and Chesters, G., 1981, Handbook of Nonpoint
Pollution Sources and Management, Van Nostrand
Reinhold Company, New York, N.Y.
MWCOG, July 1987, "Controlling Urban Runoff: A Practical
Manual for Planning and Designing Urban BMPs",
Metropolitan Washington Council of Governments Water
Resources Planning Board, Washington, D.C.
Local U.S.D.A. Soil Conservation Service offices can provide
the coefficients necessary for the USLE, models that are
based on the USLE (e.g. AGNPS), wind erosion
calculations, and SCS engineering equations.
UNIT AREA LOADING GUIDANCE
Omernik, J.M., 1977, "Non-Point Source - Stream Nutrient
Level Relationships: A Nationwide Study", EPA-600/3-
77-105, U.S. Environmental Protection Agency, Corvallis,
Oregon.
Reckhow, K.H., Beaulac, M.N., and Simpson, J.T., Jun. 1980,
"Modeling Phosphorus Loading and Lake Response
Under Uncertainty: A Manual and Compilation of Export
Coefficients", EPA-440/5-80-011, U.S. Environmental
Protection Agency Office of Water Regulations and
Standards, Washington, D.C.
-------
Rast, W., and Lee, G.F., Apr. 1983, "Nutrient Loading
Estimates for Lakes", Journal of Environmental
Engineering, Vol. 109, No. 2, pp. 502-517.
Sonzogni, W.C., Chesters, G., Coote, D.R., Jeffs, D.N.,
Konrad, J.C., Ostry, R.C., and Robinson, J.B., Feb.
1980, "Pollution from Land Runoff', Environmental
Science & Technology, Vol. 14, No. 2, pp. 148-153.
Uttormark, P.D., Chapin, J.D., and Green, K.M., Aug. 1974,
"Estimating Nutrient Loadings of Lakes from Non-Point
Sources", EPA-660/3-74-020, U.S. Environmental
Protection Agency Office of Research and Monitoring,
Washington, D.C.
RATING CURVES METHOD GUIDANCE
Mills, W.B., Porcella, D.B., Ungs, M.J., Gherini, S.A.,
Summers, K.V., Lingfung Mok, Rup, G.L., Bowie, G.L.,
and Haith, D.A., Sept. 1985, "Water Quality Assessment:
A Screening Procedure for Toxic and Conventional
Pollutants in Surface and Ground Water - Part 1", 1985
revision, EPA/600/6-85/002a, U.S. Environmental
Protection Agency Office of Research and Development,
Athens, Georgia, pp. 142-277.
Ogrosky, H.O., and Mockus, V., 1964, "Hydrology of
Agricultural Lands", Handbook of Applied Hydrology, V.T.
Chow, ed., Mcgraw-Hill, New York, N.Y.
-------
SCS, 1983, "Section 3, Sedimentation", 2nd ed., National
Engineering Handbook, U.S. Department of Agriculture
Soil Conservation Service, Washington, D.C.
Stewart, B.A., Woolhiser, D.A., Wischmeier, W.H., Caro, J.H., ^
and Frere, M.H., 1975, "Control of Water Pollution from
Croplands, Vol.1", EPA-600/2-75-026a, U.S.
Environmental Protection Agnecy, Washington, D.C.
Vanopi, V.A., ed., 1975, Sedimentation Engineering,.
American Society of Civil Engineers, New York, N.Y.
Wischmeier, W.H., and Smith, D.D., 1978, "Predicting Rainfall
Erosion Losses - A Guide to Conservation Planning",
Agriculture Handbook No. 537, U.S. Department of
Agriculture, Washington, D.C.
COMPUTER MODELS GUIDANCE
U.S. EPA, Jun. 1992, "Compendium of Watershed-Scale Xr
Models forTMDL Development", EPA841-R-92-002, U.S.
Environmental Protection Agency Office of Water,
Washington, D.C.
-------
H<7
RECEIVING WATER
MODELING
WATER QUALITY MODELING:
INTRODUCTION
Focus of
Talk:
Objective: Define relationship between pollutant
loads and receiving water quality.
Model Theory
Model Application
Available Models/Model Selection
NPS Linkage
TMDL Workshop
-------
Water Quality Model Objective
External Loadings
Environmental
Conditions
<27
Water Quality Model
Water Quality
What level of loading will result in
acceptable water quality?
TMDL Workshop
-------
RECEIVING WATER
MODELING
WATER QUALITY MODELING:
INTRODUCTION
Focus of
Talk:
Objective: Define relationship between pollutant
loads and receiving water quality.
Model Theory
Model Application
Available Models/Model Selection
NPS Linkage
TMDL Workshop
-------
Water Quality Model Objective
External Loadings
Environmental
Conditions
Water Quality Model
Water Quality
loac^u-vj
What level of loading will result in
acceptable water quality?
TMDL Workshop
-------
TYPES OF MODELS ^
0 Empirical
Predicts based on observed data
tendencies
Oft
3
C
o
c
©
o
c
o
o
r.
o
c
<0
©
2
Median total phosphorus (Tp| concentration, ug/l
Mechanistic(aka Deterministic)
Mass balance models
Accumulation = Inputs - Outputs + Reactions
cha™.
Future Amount = Present Amount + Accumulation
TMDL Workshop
-------
GENERAL MASS BALANCE MODEL
Accumulation
Mass Transfer
Loading
Kinetic Terms
Terms
Terms
/\ i/a
=
dt
Jp3kj Cj + ^Ekj(Cj - Cj)
— VkKkCk
+
w.
dQ
•dT=0
• Steady State
Conditions
Advection
Dispersion
• Decomposition
• Bio-Chemical
Transformations
• Recycle
• Settling
• Municipal
• Industrial
• Non-point
TMDL Workshop
-------
MASS BALANCE MODEL
I Accumulation = Inputs - Outputs +/- Reactions
SAVINGS ACCOUNT ANALOGY
With-
Month
Balance
Deposits
drawals
Interest
Accumulation
Jan
$1000
$10
$10
$5
5
Feb
$1005
$10
$10.05
$5.03
4.98
March
$1009.98
$10
$10.10
$5.05
4.95
TMDL Workshop
-------
LAKE ANALOGY
= Load-Outflow -Reaction
V^n- = W-QP-VkP
dt
At Steady State
1 W
J sWcU. Uad. ^ [P] =
\lct^ 1 J Q+Vk
, 7 \
\fC>\ U-;:j\c^\c'i ^VVl,r,c.yi,6\riL,l.L1
TMDL Workshop
-------
MODEL APPROACH
^^[Determine Temporal Resolution ^ ,
Determine Spatial Resolution
Define Water Movement
Define Kinetic Processes
TMDL Workshop
-------
SPATIAL RESOLUTION
Choice of model depends upon:
• Degree of mixing
• Spatial variability in concentrations
• Spatial variability of concern
"O-Dimensional - sxo^pWV
i'Ap 1 -^Kj e^W. ^ L 3 Ox/^ sWn
Slow acting pollutant or rapid mixing
Point of mix in a river, eutrophication in a lake
ox#- 1-Dimensional o<2_ \
Laterally well mixed river, downstream
decay important ^ o.
Concentrations along the length of a river
2-Dimensional
0 , AU
0(L Concentrations vary over length and width
Concentrations vary over length and depth
3-Dimensional
Concentrations vary with length, width, and depth
TMDL Workshop
-------
Examples of Different Spatial Resolution
0 - Dimensional
' 9 • *
A*
* *-* v « ft v «
~ •-•~ft*-****###.-
.¦«»*«*•*»• ¦ » < « *
OR
1 - Dimensional - -Voo
• ~ « ~
' « » •
:
» ft *
'*«««¦
•« • ft «
: •
* « *
5» '•
~ , ft
• /:-ft
ft « « ft
• . P ¦
' ~ ~
* •
• ' ' •'»
« » » •
• . •"«
9
»
« •• ft *
~ *
* • .* %.:?
ft » «. *
* * V*
•V* . - : • *$.
¦ * .• >.+:?:*
¦::: 4
• :••; •
* ¦ '
Iv * •
~ ' ' M ¦*
"~ ' •
• ••:>•:
«;.» «• •
* . .•••.=;•«
¦¦ ::::i
.**•
:\ *
«•
* » ' • *¦;.
«
~ :•
* •.
» » '« '»
• ' * ft.;:'-:
*
* •••• :;. i
*• »
• ft ft *
~ •. * •
•
~ •
«\
2 - Dimensional
2.
OR
/V/n,
* * «,.»•• ••.«. • • ? « ;
*- * «
.ft * ~ ft... ,,« ¥¦'•'.• «
p * _
fc 4 ft 'V ft'-- * '• ; 'ft :
»m*- « *' *':
' .~*.«:*. .4:.: . 4
*.' •'* . .ft
..••••: •.•.•••••.•::
J*
.V
»•: "v:;':S
,e_
T M D L Workshop
-------
j) TEMPORAL RESOLUTION
' Steady-State:
,L
Predicts concentration in response
to steady loads and environmental
conditions. ("How much?")
Easiest to apply
Limited information
1)Time Variable:
Predicts change in concentration
over time. (How much and when?)
Most difficult to apply
Detailed information
TMDL Workshop
-------
STEADY STATE VS.
TIME VARIABLE
SAVINGS ACCOUNT ANALOGY
With-
Month
Balance
Deposits
drawals
Interest
Accumulation
Jan
$1000
$10
$10
$5
5
Feb
$1005
$10
$10.05
$5.03
4.98
March
$1009.98
$10
$10.10
$5.05
4.95
Sept
$2000
$10
$20
$10
0
Accumulation = 10 - .01 (Balance) + .005 (Balance)
(change in $/mo)
Steady State Model (Accumulation =0)
0 = 10 - .01 (Balance) + .005 (Balance)
= 10 - .005 (Balance)
10
Balance = = 2000
.005
TMDL Workshop
-------
STEADY STATE VS.
TIME VARIABLE
WHEN TO USE STEADY STATE
Water quality responds immediately to changing
conditions
Point of mix in a river
Only interested in long term response
Standard expressed as annual average
Current water quality is acceptable,
how much can load be increased?
WHEN TO USE TIME VARIABLE
Water quality responds slowly to change in
load
C\r\ C\
Interested in concentration during time of
response
TMDL Workshop
-------
Varying Time Response to
Change in Model Inputs
Load
Time
Cone.
System 1
Time
Cone.
System 2
Time
TMDL Workshop
-------
HYDRODYNAMIC
CONSIDERATION
(WATER MOVEMENT)
EITHER THE EASIEST STEP OF THE
MODELING EFFORT, OR THE HARDEST.
EASY
Free flowing streams with stable flow
Qdown = Qup "*¦ Qin
OiL. Well mixed lakes
HARD
Storm surges
Embayments
Large lakes
NOTE: IF YOUR MODEL DOESN'T MOVE WATER
PROPERLY IT WILL NEVER SIMULATE QUALITY
TMDL Workshop
-------
I MIXING ZONE
ASSESSMENT
Determine pollutant concentration at the
edge of the regulatory mixing zone.
Time of travel from discharge to edge of
mixing zone is fast enough that kinetic
processes can be ignored.
~ Simple Equations
Discharge-induced vs. ambient induced
where
x = fraction of cross-sectional area
allowed for mixing
~ EPA-supported Models
CORMIX
UM/PLUMES
xQup Cup + Qw Cw
Cmix
xQup + Qw
TMDL Workshop
-------
KINETIC CONSIDERATIONS
CtL.tw^
© None
Mixing zone assessment
Conservative pollutant
(5 Some
¦^First-Order Loss
Dissolved oxygen
a Eutrophication — 'iOlcV2-\ S A
4T oxics
TMDL Workshop
-------
FIRST-ORDER LOSS ©
PROCESSES
dC! dt = -k
*
C
Change in
concentration
over time
Rate
Constant
Concentration
Loss rate is proportional to concentration. 90+% of
model kinetics are based on first-order kinetics.
100
c
o
5
0=0,6*
c
a)
o
c
o
O
n
0
Time, t (days)
10C
\c -cMo>cr2.*b^l
'YV^ >—¦8
a
In * = -kt
¦ Co
. c
In
^0
a
¦
¦
¦
Time, t
TMDL Workshop
-------
"Mechanistic" Examination
® of Dissolved Oxygen
Reaeration
1
CBOD
Degredation
Dissolved
Oxygen
Photosynthesis
w
Respiration
W
Ammonia
Nitrification
Sediment
Oxygen
Demand
TMDL Workshop
-------
SUMMARY OF DISSOLVED
OXYGEN MODEL
PROCESSES AND MODEL
INPUT PARAMETERS
Process
Reaeration
CBOD Deoxygenation
Ammonia Nitrification
SOD
Photosynthesis
Respiration
Model Inputs
Reaeration Rate
CBODult:BOD5 ratio
CBOD decay rate
CBOD settling rate
Nitrification Rate
SOD
Oxygen production rate
Oxygen consumption rate
TMDL Workshop
-------
Conceptual Framework for Eutrophication Model
0^
vv
Boundary
Conditions
Temperature
Advection and
Dispersion
External Source
Loads
Sediment Flux
Light
Water Co umn
Denitrification
N02 +
N03
CBOD
I
Settling
Denitrification
Organic N
Organic P
J
x Settling
/\ ^ Photosynthesis /
Dissolved —
Re,pi,,!,on
PhytO- | Grazing
plankton
Respiration I Decay
Settling
Zoo-
plankton
•)
SOD
Settling
Sediment
THDL Workshop
-------
(¦->0
TOXICS MODELING "
What makes toxics so special?
Toxicity
Many different chemicals
Many different loss processes
Affinity for solids
TMDL Workshop
-------
LOSS PROCESSES
(Volatilization
j Photolysis
/ Hydrolysis
I Biodegradation
Settling
(F) VOLATILIZATION
Exchange of chemical across the air-water
interface.
Information required:
Henry's law constant
Reaeration rate I' i <~i "bi L K\
Toxicant molecular weight
0 PHOTOLYSIS
Chemical breakdown of pollutant via solar energy.
TMDL Workshop
-------
Lei
Depends upon:
Quantum yield: Amount of light required to
cause a given reaction
Incoming solar radiation.
Light attenuation in water column.
• •
(n) HYDROLYSIS
Chemical reaction with water, Often accelerated by
high or low pH
Information required:
pH of receiving water
neutral hydrolysis rate
acid-catalyzed hydrolysis rate
base catalyzed hydrolysis rate
Kh=K,+K»[ir] + Kb[OH]
TMDL Workshop
-------
A /
pH
BIODEGRADATION
Bacterial degradation of pollutant
TMDL Workshop
-------
Lot
PARTITION COEFFICIENT
Ratio of sorbed to dissolved pollutant
Concentration on solids (mg/kg)
Concentration in solution (mg/l)
= Cp/[SS]
cd
Kp can be measured or estimated by
chemical (Kow) and particulate (f0c)
characteristics.
Units for Kp are inverse of the units used for
solids (l/kg or l/mg)
TMDL Workshop
-------
Suspended Solids
mg SS
liter
o
o
O
o
O
o
o
o
o
o
0
I
.o
¦
©
"G0O
® -o
© ¦
. ©
HDL Workshop
Dissolved Pollutant
[C-] =
mg Pollutant
liter
[CD] =
mg bound pollutant
liter
v =
mg bound pollutant
kg solid
[CP]
[SS]
-------
Repeat experiment with different levels of solids and polllutant, plot results
mg Pollutant
[Cd]
At low [Q ], relationship between v and [C ^ is linear
v [cpyiss]
Partition coefficient (K D Jt) = —*— =
p - [CdJ [Cd]
TMDL Workshop
-------
AFFECT OF PARTITION
COEFFICIENT OF
PERCENT PARTICULATE
DISSOLVED
Percent 1 oo Percent iCO Kp[SS]
Dissolved 1+Kp[SS] Particulate 1+Kp[SS]
f (,0
Percent
Percent
\\ SS (mg/l)
Kp
Particulate
Dissolved
$cl' (\d(j;(\ c.
Rsri.
50
1q3
' 4.8 Sl^
95.2
50
104
33.3
66.7
50
1 Q5 -h^clr^phvll'L,
83.3
16.7
1
104
1.0
99.0
10
104
9.1
90.9
100 d
104
50.0
50.0
TMDL Workshop
-------
ESTIMATION OF
PARTITION
COEFFICIENTS FOR
ORGANIC
CHEMICALS
Assumes: Chemical sorbs solely to the organic
carbon content of solids
Organic carbon partition coefficient is
equal to the octanol water partition
coefficient, Kqw
Kp
Partition
Coefficient
Kqw
foe
K ow
Octanol water
Partition Coefficient
* f
oc
Fraction organic
content of solids
Tabulated in scientific literature
for most organic chemicals
4f Wv'V O-J- SOtc.(iL
0.05 - 0.25, Water column
0.001 - 0.05, Bed sediments
Li> sVc-iaci
TMDL Workshop
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TOXIC LOSS
PROCESS SUMMARY
b --,ic!_LAgj0degradation Guesswork
Photolysis Educated guess
}o\
-------
Conceptual Framework
Toxic Chemical Model
Atmosphere
yflk.
Chemical on
Particulate Organic
Carbon
(ug/kg O.C)
Koc
Chemical in
Dissolved Phase
(ug/l)
C-(_<_C-C.
Water Column CT
C
<1)
to
1 —
0)
o.
(/)
3
O)
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MODEL APPLICATION
TOXICS
Dilution equation (C)
First-order loss models (C,S)
Partitioning-solids interactions (M) u
DISSOLVED OXYGEN
Streeter-Phelps (S,M) c¦¦ u« « tol.
Eutrophication model (M)
EUTROPHICATION
Empirical model of TP and/or chlorophyll (C)
Lakes only
Dilution model of TP (C)
First-order loss model of TP (C,S)
Eutrophication model (M)
C = Calculator
S = Spreadsheet
M = Mechanistic Model
TMDL Workshop
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IA _P
STEADY-STATE
ANALYTICAL SOLUTIONS
Predicting River Water Quality:
Cup Qup + ZCw Qw Total Load
Criver = =
Qup + Qw Total Flow
where
CUp = Upstream concentration
Qup = Upstream flow
Cw = Wastewater concentration
Qw = Wastewater flow
River Loading Capacity:
Total Load
Wiver -
Total Flow
Total Load = Criver * Total Flow
Total Allowable = Criver * Total Flow
Load
c
TMDL Workshop
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FIRST ORDER LOSS
MODEL
Required when pollutant decays significantly
between point of entry to stream and
downstream point of interest.
C(x) =
C(0) * e"kx/u
C(X) =
Concentration at distance
x downstream
C(0) =
Concentration of upstream
location
k
Pollutant decay rate
u =
Stream velocity
x/u =
Time of travel
Example:
U =
2 mi/day
k
0.5/day
X (miles)
X/U (days)
e-kx/u
(mg/l)
0
0
1
100
0.5
0.25
0.88
88
1.0
0.50
0.78
78
1.5
0.75
0.69
69
2.0
1.00
0.61
61
TMDL Workshop
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(J i
PRINCIPLE OF
SUPERPOSITION
WHEN A LINEAR RELATIONSHIP EXISTS
BETWEEN LOAD AND RECEIVING WATER
QUALITY, EACH LOADING SOURCE CAN BE
CONSIDERED INDEPENDENTLY AND THEN
SUMMED.
River
Mile
Upstream
Loading
Source 1
Loading
Source 2
Loading
Source 3
Total
Cone.
10
1.0
—
—
—
1.0
9
0.9
—
—
—
0.9
8
0.8
—
—
0.82
7
0.74
4.0
—
—
4.74
6
0.67
3.3
—
—
4.27
5
0.60
3.2
7.0
—
10.8
4
0.54
2.9
6.3
2.1
11.8
3
0.48
2.6
5.6
1.9
10.6
WORKS FOR EVERYTHING EXCEPT ALGAE
AMENABLE TO SPREADSHEET APPLICATION
TMDL Workshop
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EMPIRICAL
EUTROPHICATION
MODELING
Phosphorus
P = L / (11.6 + 1.2*qs)
where
P = Total phosphorus concentration (mg/l)
L = Phosphorus loading (g/m2 yr)
= M/A
M = Annual mass input of phosphorus to lake (g/yr)
A = Lake surface (bottom) area (m2)
qs = Annual areal water loading (m/yr)
= Q/A
Q = Annual volumetric flow rate at outlet (m3/yr)
Reckhow, K.H. 1979. Uncertainty analysis applied to
Vollenweider's phosphorus loading, criterion. Journal
Water Pollution Control Federation. Vol. 51, No. 8: 2123-
2128.
Chlorophyll
Chl a = 0.068 * P 146
Carlson, R.E. 1977. A trophic state index for lakes.
Limnol. Oceanogr. 22(2), 361-369.
TMDL Workshop
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MODEL SELECTION
Objective: Select the simplest model that includes
the relevant physical and chemical
phenomena.
Considerations
Site-specific Characteristics ••
- Physical system
- Chemistry
Management Objectives •
-Required accuracy
Project Resources;
-Data
•Staff
- Time
TMDL Workshop
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Relationship Between
Complexity and Reliability
c
© ~
o 0
Q_ OL
Complexity
Data Availability
_q
TO JS
0 0
q: a:
Complexity
0 ¦=
'JD
[to J5
0 0
C£ 01
User Understanding
Complexity
TO
_Q
ol
> 0
o 01
Complexity
TMDL Workshop
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POTENTIAL PITFALLS
1. Define objectives
No numeric water quality standards
2. Relate load to water quality
Insufficient data to develop model
Mismatch between model and water quality
standards (design conditions)
Mismatch between NPS and water quality
models
3. Define present loads
Insufficient data to define nonpoint loads
Appropriate model complexity
4. Evaluate/select control alternatives
Lack of information on BMP efficiency
5. Allocate loads
Lack of guidance on load allocation
Appropriate margin of safety
TMDL Workshop
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More Realistic TMDL Example
Water Quality Standard : 20 ug/L chlorophyll a_
: Maintenance of spawning beds for fish/
no excess siltation
: 0.02 mg/L un-ionized ammonia (chronic toxicity)
Land Use: 50% Agricultural
20% Residential
30% Urban
C
Limited data available on tributary
quality, sufficient to estimate
annual loads
No policy on allocating loads
among sources
Flow = 10 m3/sec
TMDL Workshop
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70
(jiXiUr Yr\JO',^ (5)
POTENTIAL PITFALLS
1. Define objectives
No numeric water quality standards
2. Relate load to water quality
Insufficient data to develop model
Mismatch between model and water quality
standards (design conditions)
Mismatch between NPS and water quality
models
3. Define present loads
Insufficient data to define nonpoint loads
Appropriate model complexity
4. Evaluate/select control alternatives
Lack of information on BMP efficiency
5. Allocate loads
Lack of guidance on load allocation
Appropriate margin of safety
TMDL Workshop
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More Realistic TMDL Example
Water Quality Standard : 20 ug/L chlorophyll a_
: Maintenance of spawning beds for fish/
no excess siltation
: 0.02 mg/L un-ionized ammonia (chronic toxicity)
Land Use: 50% Agricultural
20% Residential
30% Urban
Limited data available on tributary
quality, sufficient to estimate
annual loads
No policy on allocating loads
among sources
Flow = 10 m3/sec
TMDL Workshop
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71
1. WATER QUALITY STANDARDS (WQS)
LACK OF NUMERIC WATER QUALITY
OBJECTIVE
Typically associated with nutrients and/or solids
Many waters are listed as not supporting
designated uses for reasons other than violation
of water quality standards.
Siltation of spawning areas
"Excessive nutrients"
Taste and odor problems
Nuisance algal growth
Nuisance rooted plant growth
TMDL Workshop
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LACK OF NUMERIC WATER QUALITY
OBJECTIVES: SOME ALTERNATIVES
Saginaw Bay, Lake Huron: Taste and Odor
Correlate problem to amount of blue-green algae,
develop multi-species phytoplankton model to relate
phosphorus controls to blue-green algae levels.
Silver Creek, Arizona: Nutrients, Turbidity
Use existing standards from a nearby watershed.
Correlate turbidity to solids concentration.
Dillon Reservoir: Nutrients/Eutrophication
Maintain existing quality.
San Luis Obispo Creek: Nuisance Algal Growth,
Excessive Solids
Conduct instream algal assay studies to
determine relationship between nutrient
concentration and algal proliferation.
Reduce solids loading by 50%. opp^o^j^
TMDL Workshop
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- L
WATER QUALITY
MODELING PITFALLS
i-Selection of design conditions
i-Linkage between NPS and receiving water models
3 Compounding of safety factors
TMDL Workshop
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FREQUENCY/DURATION
CONSIDERATIONS OF
WATER QUALITY
STANDARDS
Water quality criteria statements should consist of
three components:
Magnitude: How much is allowed
_Or> _x .-"bz-o—'k
Duration: The period of time over which
concentrations are averaged
C KvlOrV, _ - 4--ct U—, I au- Vc- \ h r2 I Id ^
Frequency: How often criteria can be
exceeded > j
Model time scale will ideally be consistent with
duration of standard.
TMDL Workshop
-------
CONTINUOUS SIMULATION
Direct accounting for magnitude, frequency,
& duration
Continuous Simulation
Dm
pvHTr.HPPi w*m
LlfJ '
? 5 ^ S
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-
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r
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r
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r
~
m
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Data
Mass Balance Model
r S
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m
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run
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° Data
Continuous Simulation
!
S
H
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m
m
~
n
TH
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Rank and Compile
coS
ll.lll
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Downatr—w Concentration
Max
^ -1 l f1!
_ Cio i>->s j,k_
I ">
TMDL Workshop
-------
CONTINUOUS SIMULATION/
DESIGN CONDITIONS
Continuous Simulation Problems
Rarely enough data to drive model
Many nonpoint models give results on seasonal
or yearly basis
Resource-intensive to apply
Historical WLA Solution: Design Conditions
Pick single set of environmental conditions
"Critical conditions": Assume worst case
environmental condition
Design load to meet water quality standard for
critical conditions.
TMDL Workshop
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7-/
TMDL Critical Conditions
WLA
River Cone. =
VWVTP Load
River Flow
W
VWVTP
^Riv
Protect water quality at drought flow.
TMDL Workshop
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TMDL Critical Conditions
TMDL
River Cone. =
(WWTP Load + NPS Load)
River Flow
W
WWTP
What is the design condition?
TMDL Workshop
-------
7
-------
Continuous Simulation Analysis
Rainfall
NPS
Load
Stream
Flow
Time
Instream
Cone.
I\i I A\ A
Time
NPS
Model
A
Time
VWVTP
Load
WQ
Model
Time
Time
TMDL Workshop
-------
Long Criteria Durations Facilitate
Continuous Simulation Analysis
-J(r
Rainfall
Stream
Flow
NPS
Load
Time
NPS
Model
Time
VWVTP
Load
Time
WQ
Model
Instream
Cone.
Time
T M D L Workshop
Time
-------
LINKAGE BETWEEN NPS
AND RECEIVING WATER
MODELS
Need Consistency in: \ ^ souf
Parameters
Temporal Resolution
Spatial Domain
Level of Complexity
Nonpoint
Source
Model
o
u
T
P
u
T
Receiving Water
Model
TMDL Workshop
-------
ft ¦
|\\Ktyw ^iiwlc
REFORMATTING NPS
OUTPUTS
. pL.
SWMM OUTPUT l'
Junction 7 Junction 8
Time Flow Cone. Load Flow Cone. Load
0.0 — — 0.0 — — 0.0
1.0 — — 63.4 — — 12.9
2.0 — — 58.6 — — 15.6
3.0 — — 46.1 — — 16.8
4.0 — — 29.2 — — 14.3
5.0 — — 18.6 — — 12.1
6.0 — — 12.1 — — 3.0
7.0 — — 0.0 — — 0.0
WASP INPUT
5 (Number of segments receiving loads)
1.0 1.0 (Scale and unit conversion factors)
5 (Model segment)
8 (Number of points in series)
O.O(Time) O.O(Load) 1.0(Time) 63.4(Load) 2.0 58.6 3.0 46.1 4.0 29.2
5.0 18.6 6.0 12.1 7.0 0.0
7 (Model segment)
8 (Number of points in series)
O.O(Time) O.O(Load) 1.0(Time) 12.9(Load) 2.0 15.6 3.0 16.8 4.0 14.3
5.0 12.1 6.0 3.0 7.0 0.0
T M D L Wo r k s h o p
-------
COMPOUNDING OF SAFETY
FACTORS
EPA permitting procedures state that effluent
concentration should exceed WLA only 1% (or 5%)
of the time.
This works fine for a single discharge, however, the
probability than 10 discharges in a watershed all
simulataneously at 99,h% is
0.0000000000000000001 percent!
Solution: Dynamic modeling (Continuous Simulation
or Monte Carlo)
T M D L W o r k s h o p
-------
~n
SELECTION OF
CRITICAL CONDITIONS
Examples
Silver Creek
Water quality standard = annual average.
Paradise Creek
Water quality goals defined on climatic
season basis.
San Luis Obispo Creek
Annual average.
Lake Lanier
Critical period approach.
TMDL Workshop
-------
TMDL UNCERTAINTY/
MARGIN OF SAFETY
TMDLs must contain a margin of safety
(MOS) to account for uncertainty in predicted
relationship between pollutant loads and
receiving water quality.
Can be accounted for implicitly or explicitly
Explicit Example
Loading Capacity = WLA + LA + MOS
100 kg/day = 40 + 40 + 20
TMDL Workshop
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77
IMPLICIT CONSIDERATION
OF MARGIN OF SAFETY
Incorporate Conservative Assumptions in
Modeling Analysis
Conservative design conditions
Conservative pollutant decay rates
LC = WLA + LA
LC= 100+/-20
80 = 40 + 40
TMDL Workshop
-------
TECHNICAL
RAMIFICATIONS OF
MARGIN OF SAFETY
As uncertainty increases, allocatable load
shrinks in comparison to MOS
LC = WLA + LA
100+90= 5 +5
Stakeholders reluctant to implement required
controls, as severity of reductions is directly
proportional to uncertainty of analysis.
BPJ often required. ~"W\ v\_\ya/a
TMDL Workshop
-------
MARGIN OF SAFETY
Often included by assuming no instream
loss processes
Hater profile. Total Toxicant
Lower Colunbia River
°'20\U loss.
I No_1obs
0.16
~ .08
~ .04
O.OO
160
300
260
5&
River Rile
Conparison of Results for Alternative Loss Assunptions
TMDL Workshop
-------
MARGIN OF SAFETY
Need to estimate magnitude of loss processes,
to determine significance of neglecting them
Hater profile. Total Toxicant
Blackstone River Julu Run
AO n=
H lo»».
I no_loss.
8
6
4
2
O
I'd
River Mile
To
Predicted Lead Concentrations with Alternative Loss Assunpt ions
TMPL Workshop
-------
PHASED APPROACH TO
TMDL DEVELOPMENT
Develop preliminary TMDL
Replace rigorous models with simple
(yet reasonable) screening methods
Implement control strategies
Monitor to determine if water quality
objectives are achieved
Perform more rigorous modeling, if necessary
TMDL Workshop
-------
Spatial Considerations
of TMDL Assessment
Need to consider water quality at multiple locations
in the watershed, not just at the outlet
o Major load entry points
o Subwatershed outlets
TMDL Workshop
-------
•5 7.
Technical Considerations
Associated with TMDL Trading
Magnitude of TMDL may depend upon where the
load enters stream
lysfssfiytis//,
, SXS S V> S ,
i *>N
v-
LA=50 kg/day WLA=100 kg/day WU\=100 kg/day WL^=100 kg/day
TMDL = 350 kg/day
We can redistribute this load, and violate WQS
WQS
Cone.
LA=50 kg/day
WLA=200 kg/day
WLA=50 kg/day
WLA=50 kg/day
Need to consider all locations in the
receiving water, not just watershed outlet
TMDL Workshop
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PRACTICAL APPROACH
TO DEALING WITH
PITFALLS
Define problem
In what way can problem be solved
What are the resources required.
What problems does this solution introduce
sensitivity analyses
Which alternative provides best mix of costs
and benefits
The more simplifying assumption(s) required,
more likely that only a phased TMDL can
be conducted.
TMDL Workshop
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REAL WORLD EXAMPLES
OF
PRACTICAL
CONSIDERATIONS
Silver Creek, AZ
Land use: Forest, rangeland
WQ Issues: Solids, nutrients
Paradise Creek, ID/WA
Land use: Agriculture, urban
WQ Issues: Solids, nutrients
San Luis Obispo Creek, CA
Land use: Agriculture, urban
WQ Issues: Solids, nutrients
TMDL Workshop
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