Water Quality Modeling:
Estimating Pollutant Load Reductions for
Project Reporting
Scott Daly
Utah Division of Water Quality
801.536.4333
sdaly@utah.gov
Objective
•
UAFRRI – Utah Animal Feedlot Runoff Risk Index
–
–
•
Overview
Data Inputs
STEPL – Spreadsheet Tool for Estimating Pollutant
Loads
1.
2.
3.
4.
5.
•
•
Overview
Data Inputs
Model Setup
Limitations
Data Sources
WQ Models and Project Planning
Discussion
Utah Animal Feedlot Runoff Risk
Index (UAFRRI)
• MS Excel spreadsheet
• Nutrient loading and load reduction
estimates (N, P, and BOD5)
• Feedlot Risk Assessment
Spreadsheet Tool for Estimating
Pollutant Loads
(STEPL)
• MS Excel spreadsheet
– Easy to use
– Inputs can be modified by user (optional)
• Calculates nutrient (N, P, and BOD5) and
sediment loads by land use type
• Calculates expected load reductions
• Data driven and highly empirical
STEPL Process
User Input
Processes
Land Uses
Runoff
Animals
Groundwater
Precipitation
Irrigation
Sheet/Rill
Erosion
Load
Nitrogen
BMPs/LIDs
Phosphorus
Soil and USLE
Parameters
Septic Systems
Direct Discharges
BOD
Gully/
Streambank
Erosion
Pollutant
Transport
Sediment
Load
Reduction
STEPL Web Site
Link to
download
URL: http://it.tetratech-ffx.com/stepl
STEPL Main Program
• Run STEPL executable program (STEPL.exe)
• Start All Programs STEPL
STEPL Spreadsheet
Composed of four worksheets
Data Input
Universal Soil Loss Equation
(RUSLE)
• USLE = R*K*LS*C*P
Where:
•
•
•
•
•
R = rainfall and runoff factor
K = soil erodibility factor
LS = slope length and steepness factor
C = cover management factor
P = support practice factor
• USLE – LS Factor
C over m anagem ent, “C ” factors fo r perm anent pasture, ran geland, and idle land.
__________________________________________________________________________
V egetal C ano p y
Typical USLE C
and P Values
C o ver T hat C o ntacts the S urfa ce
T yp e and H eig ht
C ano p y
P ercent G ro und C o ver
2
3
4
o f R aised C a no p y
C o vers %
T yp e
0
20
40
60
80
9 5 -1 0 0
_ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ _ _ __ _ __ _ __ _ __ _ __ _ __
N o ap p reciab le cano p y
G
.4 5
.2 0
.1 0
.0 4 2
.0 1 3
.0 0 3
W
.4 5
.2 4
.1 5
.0 9 0
.0 4 3
.0 1 1
C ano p y o f tall w eed s
o r sho rt b rush,
0 .5 m (1 .6 ft.) fall ht.
25
50
75
A p p reciab le b rush
o r b ushes,
2 m 6 .6 ft. fall ht.
25
50
75
T rees b ut no ap preciab le,
lo w b rush ,
4 m (1 3 .1 ft.) fall h t.
Support Practice Factor
S u p p o rt P ra c tic e
U p & D o w n S lo p e
C ro ss S lo p e
C o n to u r fa rm in g
S trip cro p p in g , cro ss slo p e
S trip cro p p in g , co n to u r
.3 6
.3 6
.2 6
.2 6
.1 7
.1 7
.1 7
.2 0
.1 3
.1 6
.1 0
.1 2
.0 9
.1 3
.0 7
.1 1
.0 6
.0 9
.0 3 8
.0 8 2
.0 3 5
.0 7 5
.0 3 1
.0 6 8
.0 1 2
.0 4 1
.0 1 2
.0 3 9
.0 1 1
.0 3 8
.0 0 3
.0 1 1
.0 0 3
.0 1 1
.0 0 3
.0 1 1
G
W
G
W
G
W
.4 0
.4 0
.3 4
.3 4
.2 8
.2 8
.1 8
.2 2
.1 6
.1 9
.1 4
.1 7
.0 9
.1 4
.0 8 5
.1 3
.0 8
.1 2
.0 4 0
.0 8 5
.0 3 8
.0 8 1
.0 3 6
.0 7 7
.0 1 3
.0 4 2
.0 1 2
.0 4 1
.0 1 2
.0 4 0
.0 0 3
.0 1 1
.0 0 3
.0 1 1
.0 0 3
.0 1 1
G
.4 2
.1 9
.1 0
.0 4 1
.0 1 3
.0 0 3
W
.4 2
.2 3
.1 4
.0 8 7
.0 4 2
.0 1 1
50
G
.3 9
.1 8
.0 9
.0 4 0
.0 1 3
.0 0 3
W
.3 9
.2 1
.1 4
.0 8 5
.0 4 2
.0 1 1
75
G
.3 6
.1 7
.0 9
.0 3 9
.0 1 2
.0 0 3
W
.3 6
.2 0
.1 3
.0 8 3
.0 4 1
.0 1 1
_ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ _ _ __ _ __ _ __ _ __ _ __ _ __ _ __ __ _ _ __ _ __ _ __ _ __ _ __ _
P F a c to r
1
0 .7 5
0 .5
0 .3 7
0 .2 5
25
G
W
G
W
G
W
Optional Input Data
SCS Curve Number – Hydrologic
Soil Group
• Group A –Low overland Flow; high infiltration
capacity; well-drained (Sand and Gravel)
• Group B –Moderate minimum infiltration
capacity; moderately- to well- drained;
moderately-course grained (Sandy Loam)
• Group C – Low minimum infiltration capacity;
moderately fine- to fine-grained soils
• Group D – very low infiltration capacity; high
overland flow potential (Clay)
Curve Numbers for Arid and Semiarid Rangelands
Hydrologic
Soil Hydrologic
Land Use/Cover
Condition
Group
A
B
C
------------------------------------------------------------------------------------------------------------------------------------------Herbaceous - grass, weeds & lowPoor /a
80
87
growing brush; brush the minor
Fair
71
81
component
Good
62
74
93
89
85
Oak/aspen - oak brush, aspen, Poor
mountain mahogany, bitter brush,
maple and other brush
D
Fair
Good
-
66
48
30
74
57
41
79
63
48
Pinyon/juniper - pinyon, juniper or
both; grass understory
Poor
Fair
Good
-
75
58
41
85
73
61
89
80
71
Sagebrush with grass understory
Poor
Fair
Good
-
67
51
35
80
63
47
85
70
55
Desert scrub - saltbush, greasewood,
Poor
63
77
85
88
creosotebrush, blackbrush, bursage,
Fair
55
72
81
86
palo verde, mesquite and cactus
Good
49
68
79
84
-----------------------------------------------------------------------------------------------------------------------------------a. Poor: < 50% ground cover (litter, grass and brush overstory); Fair: 50 to 75% ground cover; Good: 75% ground cover.
•SCS Curve Number Computations.pdf Appendix A Table 2-2
CN - Antecedent Moisture
Conditions
C u rve N u m b e rs
C o n d itio n II C o n d itio n I C o n d itio n III
100
100
100
95
87
98
90
78
96
85
70
94
80
63
91
75
56
88
70
51
85
65
45
82
60
40
78
55
35
74
50
31
70
45
26
65
40
22
60
35
18
55
30
15
50
25
12
43
20
9
37
15
6
30
10
4
22
5
2
13
Populate STEPL Input Tables
BMPs
Urban BMP Tool
Gully/Streambank Loading
Add New Data to BMP List
• In STEPL customized menu, click “View/Edit BMP List”
• BMP List worksheet is shown, add or delete BMPs
BMP Efficiency Calculator
Add New Data to BMP List
Update BMP button
(BMPList worksheet)
New BMP added!
New BMP added!
(BMPs worksheet)
• Click “Update BMP Data” button to update the BMP
selections in the BMPs worksheet
• Click “Save Updates” to save changes to text files
(comma delimited)
– C:or D:\Stepl\Support\AllBMPstepl.csv
– C: or D:\Stepl\Support\AllBMP.csv
STEPL BMP Calculator
• Calculates combined efficiency of a BMP train for a
given land use.
STEPL BMP Calculator
Reduced tillage
Series
Parallel
Conventional
tillage
Reduced tillage
Filter strip
Conventional
tillage
Settling Basin
Reduced tillage
Filter strip
Combination
STEPL BMP Calculator
• Describe schematically BMP configuration
– Number and linkages
– BMP type and efficiency
– Land use area
4. Calculate
combined efficiency
1. Add BMP box
• Calculate combined
5. Delete Connection
efficiency
• Enter calculated efficiency
in table 7 on the BMP tab
2. Draw Connection
3. Move BMP box
BMP Calculator - Series
3
2
1
Reduced
Tillage
Filter Strip
Load
BMP Calculator - Parallel
3
1
2
Each box represents 100 ac
Streambank
Stabilization
Load
Contour
Farming
Populate STEPL BMP Tables
Total Load
Graphs
Other Ways to Use STEPL
• Model changes in land use and runoff
before and after BMPs instead of modeling
efficiencies
• Estimate BMP efficiencies
BMP efficiency = (Pre BMP load – Post BMP load) / Pre BMP load
• Project planning
STEPL as a Project Planning Tool
• Compare two projects to determine which
has the most potential for load reduction
• Compare multiple BMPs within the same
project area
Model Limitations
• Driven by empirical relationships
– Emphasis for project-specific data
• Model calibration/validation
– Not easy to calibrate
• Designed to produce “rough” loading
estimates, NOT accurate or precise
estimates
Discussion
Data Resources
Table 1. Input watershed land use area (ac) and precipitation (in)
1. Precipitation: (a). Local observation (b). http://www.wrcc.dri.edu/
(c). http://www.wcc.nrcs.usda.gov/snow/ (d). nws.noaa.gov
Table 4. Modify the Universal Soil Loss Equation (USLE)
parameters
1. K Factor - http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm
2.
LS Factor – Field measurements for slope length (L) and slope
(S), then
consult the following tables. USDA Agricultural
Handbook 703: Tables
4-1 through 4-9.
3.
Cover Management Factor – USLE Appendix A - Cover
Managment Factor.doc and
http://www.iwr.msu.edu/rusle/doc/cfactors.pdf
4.
Support Practice Factor –
http://www.omafra.gov.on.ca/english/engineer/facts/00-001.htm
Table 5
Data Resources
•
Table 6. Reference runoff curve number (may be modified)
1. SCS Runoff Curve Number Computations.pdf, Appendix A Table 2-2