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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
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Water Quality Modeling:Estimating Pollutant Load Reductions for Project ReportingScott DalyUtah Division of Water Quality801.536.4333sdaly@utah.gov
Objective • UAFRRI – Utah Animal Feedlot Runoff Risk Index • Overview • Data Inputs • STEPL – Spreadsheet Tool for Estimating Pollutant Loads • 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 Processes Load User Input Land Uses Runoff BMPs/LIDs Nitrogen Animals Groundwater Sheet/Rill Erosion Phosphorus • Precipitation • Irrigation Load Reduction BOD Soil and USLE Parameters Gully/ Streambank Erosion Sediment • Septic Systems • Direct Discharges Pollutant Transport
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
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
Typical USLE C and P Values Support Practice Factor
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 Semi-arid Rangelands Hydrologic Soil Hydrologic Land Use/Cover Condition Group A B C D ------------------------------------------------------------------------------------------------------------------------------------------- Herbaceous - grass, weeds & low- Poor /a - 80 87 93 growing brush; brush the minor Fair - 71 81 89 component Good - 62 74 85 Oak/aspen - oak brush, aspen, Poor - 66 74 79 mountain mahogany, bitter brush, Fair - 48 57 63 maple and other brush Good - 30 41 48 Pinyon/juniper - pinyon, juniper or Poor - 75 85 89 both; grass understory Fair - 58 73 80 Good - 41 61 71 Sagebrush with grass understory Poor - 67 80 85 Fair - 51 63 70 Good - 35 47 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
Add New Data to BMP List • In STEPL customized menu, click “View/Edit BMP List” • BMP List worksheet is shown, add or delete BMPs
Add New Data to BMP List Update BMP button (BMPList 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 New BMP added! (BMPs worksheet) New BMP added!
STEPL BMP Calculator • Calculates combined efficiency of a BMP train for a given land use.
Series Reduced tillage Parallel Conventional tillage Reduced tillage Conventional tillage Reduced tillage Filter strip Settling Basin Combination STEPL BMP Calculator Filter strip
STEPL BMP Calculator • Describe schematically BMP configuration • Number and linkages • BMP type and efficiency • Land use area • Calculate combined efficiency • Enter calculated efficiency in table 7 on the BMP tab 4. Calculate combined efficiency 1. Add BMP box 5. Delete Connection 2. Draw Connection 3. Move BMP box
BMP Calculator - Series 3 1 2 Reduced Tillage Filter Strip Load
BMP Calculator - Parallel 3 1 2 Each box represents 100 ac Streambank Stabilization Contour Farming Load
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
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 • K Factor - http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm • 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. • Cover Management Factor – USLE Appendix A - Cover Managment Factor.doc and http://www.iwr.msu.edu/rusle/doc/cfactors.pdf • Support Practice Factor – http://www.omafra.gov.on.ca/english/engineer/facts/00-001.htm Table 5 • Table 5. Select average soil hydrologic group (SHG) • Soil Hydrologic Group = Hydrologic Soil Group • http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm
Data Resources • Table 6. Reference runoff curve number (may be modified) 1. SCS Runoff Curve Number Computations.pdf, Appendix A Table 2-2