BMP Evaluations Using SWAT Model and Associated Uncertainties<br />A. Shirmohammadi and T. W. Chu.<br />Biological Resourc...
“Forests and wetlands trap sediments and help slow the flow of pollutants into the Bay.  Their loss, coupled with the decl...
Ecological Resilience: Provides a measure of the amount of disturbance that an ecosystem can withstand without shifting in...
For Bay: “The shift from a food web dynamic driven by benthic processes- such as underwater grasses and oysters- to one dr...
Identifying Thresholds: “Researchers must develop a systematic way to anticipate when a system is getting close to a thres...
Background<br />Hydrologic/ water quality models are the main tools used to tabulate total maximum daily loads (TMDLs)<br ...
Background<br />General expression for TMDL allocations:<br />TMDL=ΣWLA + ΣLA + Future Growth + MOS<br />Waste Load Alloca...
Background<br />Types of Uncertainty in Modeling<br />Model Structure<br />Parameter Values<br />Natural Variability (Spat...
Watershed/Basin Scale Model<br />SWAT<br />(Arnold et al., 1998)<br />
Data Source:<br />Study Site: <br />Warner Creek Watershed<br />
Data Collection:<br /><ul><li>Precipitation
Stream flow
Sediment
NO3-N
NH4-N
TKN
PO4-P
TP</li></li></ul><li>Location:Frederick County, Maryland<br />Area:346 ha (856 acres)<br />Soil Type:1/3 Area:  Manor-Edge...
Background on SWAT Model<br />
Components of SWAT Model<br />Hydrology<br />Sedimentation (Erosion)<br />Nutrients<br />Pesticides<br />Bacteria<br />
Calibration period (1994-1995).<br />Validation period (1996-2002).<br />
Table. Statistical results comparing measured and simulated flow data at station 2A after adjustment to the subsurface flo...
-<br />NO3 - N Statistics<br />
List of BMPs Simulated<br />
Total areas for row crops planting within Warner watershed<br />
Results of BMP Simulation <br />
Comparison of annual total streamflow at the outlet of the watershed based on different BMP implementations.<br />*Backgro...
Comparison of annual surface runoff at the outlet of the watershed based on different BMP implementations.<br />*Backgroun...
Comparison of annual surface runoff at the outlet of the watershed based on different BMP implementations without winter c...
Comparison of annual sediment loading at the outlet of the watershed based on different BMP implementations.<br />*Backgro...
Comparison of annual nitrate nitrogen loading at the outlet of the watershed based on different BMP implementations.<br />...
Comparison of annual soluble phosphorus loading at the outlet of the watershed based on different BMP implementations.<br ...
Comparison of average annual (1994-2002) model prediction at the outlet of the watershed based on different BMP implementa...
Latin Hypercubic Sampling<br />For Model Uncertainty<br />
Latin Hypercube Sampling (LHS)<br />n=5<br />Uniform distribution<br />Normal distribution<br /><ul><li>Divided into n non...
One value from each interval is then selected randomly with respect to the probability density in the interval.  </li></li...
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Shirmohammadi

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Shirmohammadi

  1. 1. BMP Evaluations Using SWAT Model and Associated Uncertainties<br />A. Shirmohammadi and T. W. Chu.<br />Biological Resources Engineering Department<br />University of Maryland, College PArk<br />
  2. 2. “Forests and wetlands trap sediments and help slow the flow of pollutants into the Bay. Their loss, coupled with the decline of grasses and oysters in the 1970s and 1980s, caused the Bay to lose much of its resilience.”<br />Chesapeake Quarterly<br />MD Sea Grant College, Vol. 3, Num. 3<br />October 2004<br />
  3. 3. Ecological Resilience: Provides a measure of the amount of disturbance that an ecosystem can withstand without shifting into an “alternate stable state”<br />
  4. 4. For Bay: “The shift from a food web dynamic driven by benthic processes- such as underwater grasses and oysters- to one driven by phytoplankton in the water column is a classic example of regime shift, a shift between stable states.” <br />
  5. 5.
  6. 6. Identifying Thresholds: “Researchers must develop a systematic way to anticipate when a system is getting close to a threshold or tipping point and prevent it from going over the edge. They also need to develop methods to turn around the state of a system such as the Chesapeake Bay from undesirable to desirable!” ---Load Reduction! <br />
  7. 7. Background<br />Hydrologic/ water quality models are the main tools used to tabulate total maximum daily loads (TMDLs)<br />Procedure for tabulating TMDLs <br />Use monitored data as input into model to represent base conditions<br />Simulate alternate management scenarios<br />Choose management scenario that meets water quality standards<br />Determine total load and allocate load among sources<br />
  8. 8. Background<br />General expression for TMDL allocations:<br />TMDL=ΣWLA + ΣLA + Future Growth + MOS<br />Waste Load Allocations (WLA)- point source contributions<br />Load Allocations (LA)- non-point source contributions including background sources<br />Margin of Safety (MOS)- accounts for uncertainties about the relationship between pollutant loads and receiving water quality (USEPA, 1999a)<br />
  9. 9. Background<br />Types of Uncertainty in Modeling<br />Model Structure<br />Parameter Values<br />Natural Variability (Spatial and Temporal)<br />Data Uncertainty<br />Model Prediction<br />
  10. 10. Watershed/Basin Scale Model<br />SWAT<br />(Arnold et al., 1998)<br />
  11. 11. Data Source:<br />Study Site: <br />Warner Creek Watershed<br />
  12. 12. Data Collection:<br /><ul><li>Precipitation
  13. 13. Stream flow
  14. 14. Sediment
  15. 15. NO3-N
  16. 16. NH4-N
  17. 17. TKN
  18. 18. PO4-P
  19. 19. TP</li></li></ul><li>Location:Frederick County, Maryland<br />Area:346 ha (856 acres)<br />Soil Type:1/3 Area: Manor-Edgemont-Brandywine; 2/3 Area: Penn-Readington-Croton<br />Slope:95% Area: Slope <15%, 5% Area: Slope between 15 and 25%<br />Erodibility:65% Area: Moderately erodible; 12% Area: Severely erodible; 23% Area: classified not erodible<br />Land Use:Pasture, Dairy, Beef, Cropland<br />
  20. 20.
  21. 21. Background on SWAT Model<br />
  22. 22. Components of SWAT Model<br />Hydrology<br />Sedimentation (Erosion)<br />Nutrients<br />Pesticides<br />Bacteria<br />
  23. 23.
  24. 24. Calibration period (1994-1995).<br />Validation period (1996-2002).<br />
  25. 25.
  26. 26. Table. Statistical results comparing measured and simulated flow data at station 2A after adjustment to the subsurface flow contribution from outside the watershed. <br />
  27. 27.
  28. 28.
  29. 29.
  30. 30. -<br />NO3 - N Statistics<br />
  31. 31.
  32. 32. List of BMPs Simulated<br />
  33. 33. Total areas for row crops planting within Warner watershed<br />
  34. 34. Results of BMP Simulation <br />
  35. 35. Comparison of annual total streamflow at the outlet of the watershed based on different BMP implementations.<br />*Background: up and downhill planting with conventional tillage<br /> BMP1: contour planting with conventional tillage<br /> BMP2: contour planting with conservation tillage <br /> BMP3: contour planting with no-till <br /> BMP4: contour stripcropping with no-till <br />
  36. 36. Comparison of annual surface runoff at the outlet of the watershed based on different BMP implementations.<br />*Background: up and downhill planting with conventional tillage<br /> BMP1: contour planting with conventional tillage<br /> BMP2: contour planting with conservation tillage <br /> BMP3: contour planting with no-till <br /> BMP4: contour stripcropping with no-till <br />
  37. 37. Comparison of annual surface runoff at the outlet of the watershed based on different BMP implementations without winter crop planting .<br />*Background: up and downhill planting with conventional tillage<br /> BMP1: contour planting with conventional tillage<br /> BMP2: contour planting with conservation tillage <br /> BMP3: contour planting with no-till <br /> BMP4: contour stripcropping with no-till <br />
  38. 38. Comparison of annual sediment loading at the outlet of the watershed based on different BMP implementations.<br />*Background: up and downhill planting with conventional tillage<br /> BMP1: contour planting with conventional tillage<br /> BMP2: contour planting with conservation tillage <br /> BMP3: contour planting with no-till <br /> BMP4: contour stripcropping with no-till <br />
  39. 39. Comparison of annual nitrate nitrogen loading at the outlet of the watershed based on different BMP implementations.<br />*Background: up and downhill planting with conventional tillage<br /> BMP1: contour planting with conventional tillage<br /> BMP2: contour planting with conservation tillage <br /> BMP3: contour planting with no-till <br /> BMP4: contour stripcropping with no-till <br />
  40. 40. Comparison of annual soluble phosphorus loading at the outlet of the watershed based on different BMP implementations.<br />*Background: up and downhill planting with conventional tillage<br /> BMP1: contour planting with conventional tillage<br /> BMP2: contour planting with conservation tillage <br /> BMP3: contour planting with no-till <br /> BMP4: contour stripcropping with no-till <br />
  41. 41.
  42. 42.
  43. 43.
  44. 44.
  45. 45.
  46. 46. Comparison of average annual (1994-2002) model prediction at the outlet of the watershed based on different BMP implementations with and without winter crop planting<br />
  47. 47. Latin Hypercubic Sampling<br />For Model Uncertainty<br />
  48. 48. Latin Hypercube Sampling (LHS)<br />n=5<br />Uniform distribution<br />Normal distribution<br /><ul><li>Divided into n non-overlapping intervals on the basis of equal probability.
  49. 49. One value from each interval is then selected randomly with respect to the probability density in the interval. </li></li></ul><li>Model output distribution of Streamflow at the watershed outlet<br />
  50. 50. Model output distribution of Sediment loading at the watershed outlet<br />
  51. 51. Model output distribution of Nitrate loading at the watershed outlet<br />
  52. 52. Model output distribution of Streamflow at the watershed outlet<br />1004<br />BMP4<br />BMP4 (1996)<br />
  53. 53. Model output distribution of Nitrate loading at the watershed outlet<br />BMP4 (1996)<br />BMP4 (1996) without winter crop<br />
  54. 54. Acknowledgement<br />Our Cooperator,<br />Dr. Linda Abbot of USDA/OCE/ORACBA<br />
  55. 55. Model output distribution of Sediment loading at the watershed outlet<br />BMP2<br />BMP4 (1996)<br />

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