Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/19/2006
Publication Date: 4/1/2007
Citation: Larose, M., Heathman, G.C., Norton, L.D., Engel, B. 2007. Hydrologic and atrazine simulation in the Cedar Creek Watershed using the SWAT model. Journal of Environmental Quality. 36:521-531. Interpretive Summary: The release and migration of nutrients, pesticides and other chemicals from agricultural lands is a great loss of resources and a threat to the quality of our surface and ground waters. Water quality modeling can be used to simulate the fate and transport of chemicals from agricultural lands at the watershed scale and help determine areas of greatest loss. Once problem areas have been identified, conservation practices may be initiated that should reduce the amount of chemical loss in runoff. In this study, the Soil and Water Assessment Tool (SWAT) model was used to estimate atrazine losses in the Cedar Creek Experimental Watershed within the St. Joseph River Basin in northeastern Indiana. Model performance was tested by comparing model estimates of streamflow and atrazine concentrations to USGS measured streamflow and atrazine data. Results of the study show that the model provided adequate estimates of streamflow and atrazine concentrations. The greatest loss of atrazine occurred shortly after application and during a significant rainfall event. The impact of this work is demonstrating how the SWAT model may be used to evaluate the effects of different management practices in the Midwest on atrazine loss in runoff at the watershed scale.
Technical Abstract: One of the major factors contributing to surface water contamination in agricultural areas is the use of pesticides. The Soil and Water Assessment Tool (SWAT) is a hydrologic model capable of simulating the fate and transport of pesticides in an agricultural watershed. SWAT was used in this study to estimate streamflow and atrazine losses to surface water in the Cedar Creek Experimental Watershed (CCEW) within the St. Joseph River Basin in northeastern Indiana. Model calibration and validation procedures consisted of five and two year periods, respectively. The National Agricultural Statistics Survey (NASS) 2001 land cover classification and the Soil Survey Geographic (SSURGO) database were used as model input data layers. Data from the St. Joseph River Watershed Initiative and the Soil and Water Conservation Districts of Allen, Dekalb and Noble counties were used to represent agricultural practices in the watershed which included the type of crops grown, different tillage practices, and fertilizer and pesticide application rates. Model results were evaluated based on efficiency coefficient values, standard statistical measures, and visual inspection of the measured and simulated hydrographs. The Nash-Sutcliffe model efficiency coefficients (ENS) for both monthly and daily streamflow were 0.66. For the two-year validation period, the ENS values for monthly and daily streamflow were 0.56 and 0.51, respectively. The ENS values for atrazine calibration and validation ranged from 0.43 to 0.59. All ENS values were within the range of acceptable model performance standards. The results of this study indicate that the model is an effective tool in simulating water yield and pesticide loss, as well capturing the dynamics of streamflow and atrazine concentrations on a large-scale agricultural watershed.