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Evaluation of SWAT in Simulating Atrazine Losses in Stream Discharge for Walnut Creek Watershed (Iowa)

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:10.13031/2013.18112)
Authors:   B. Du, A. Saleh, D.B. Jaynes and J.G. Arnold
Keywords:   Water quality, modeling, subsurface flow, tile drainage, pothole, watershed, SWAT

The Soil and Water Assessment Tool (SWAT) has been enhanced with modified tile drain and pothole components and evaluated for its capability of simulating flow and nitrate nitrogen in stream discharge. This study evaluated the performance of the enhanced SWAT model in simulating atrazine loads at a watershed scale using ten years of measured data from the Walnut Creek watershed (WCW) in central Iowa. The enhanced SWAT was calibrated to data from the period of 1992 to 1995 and verified to data from the period of 1996 to 2001. The Nash- Sutcliffe E value and the relative mean error (RME) were used to measure model performance. Overall, the results of this study indicated that SWAT simulated relatively well the patterns and amounts of the monthly flow and atrazine load in the gently rolling landscape of WCW where tile drains and potholes are common (E values for the predicted monthly flow ranged from 0.72 to 0.89 and RME values from 19% to 16%; E and RME values for the predicted monthly atrazine loads varied from 0.66 to 0.90 and from 19% to 16%, respectively). However, compared to the monthly results, daily flow and atrazine loads predicted by the modified SWAT were less accurate.

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