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INFLUENCE OF HYDROLOGIC RESPONSE UNIT (HRU) DISTRIBUTION ON SWAT MODEL FLOW AND SEDIMENT PREDICTIONS

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Watershed Management to Meet Water Quality Standards and Emerging TMDL (Total Maximum Daily Load) Proceedings of the Third Conference 5-9 March 2005 (Atlanta, Georgia USA) Publication Date 5 March 2005  701P0105.(doi:10.13031/2013.18081)
Authors:   Kati L White and Indrajeet Chaubey
Keywords:   SWAT model, Monte Carlo simulations, spatial variability, uncertainty, watershed

The Soil and Water Assessment Tool (SWAT) model was implemented in the Illinois River watershed in Northwest Arkansas to investigate flow and sediment predictive ability at multiple subbasin and HRU distributions. Our objectives were to: 1) spatially characterize the watershed using two different subbasin delineations with six different HRU combinations for each; 2) identify the two parameters that most influenced predicted flow volume and predicted sediment load; 3) characterize the two parameters identified in objective 2 as a distribution instead of a discrete value; 4) simulate each different subbasin/HRU SWAT model combination using Monte Carlo simulations; and 5) compare predicted annual flow volume and sediment yield for each subbasin/HRU combination to measured values identifying differences amongst the group. The curve number and the soil evaporation compensation factor were found to have the greatest influence on the predicted variables of interest and were described as a distribution. The SFBSAOV test results indicated a failure to reject the null hypothesis that the means were different amongst all predicted flow values, suggesting that all predicted population means were similar or not significantly different from each other. Sediment results indicated that the null hypothesis could be rejected and hence the sediment means were significantly different amongst the different model subbasin/HRU delineations and measured values. Future investigation is needed to determine if spatial characterization of a SWAT model will influence the users ability to calibrate. In addition, further study is needed to assess the influence subbasin delineations and HRU distributions have on predicted nutrient yields.

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