Off-site transport of pesticides from treated agricultural fields to receiving water bodies is most often associated with surface runoff and erosion processes, as well as spray drift. Movement of pesticide in the subsurface is typically studied to assess the potential for leaching to groundwater, but this process is rarely evaluated as a potential pathway to surface water. The potential for pesticides to reach surface waters via the subsurface can be enhanced and expedited by the presence of subsurface tile drainage systems that are designed to more rapidly drain water from the soil to receiving water ditches and receiving waters. The relative importance of this potential transport pathway, relative to surface processes, is dependent upon both the environmental characteristics (soils and climate) and the pesticide characteristics (environmental fate properties and application methods). More persistent and mobile compounds, applied at depth in the soil, are at greater risk for subsurface transport. Modeling approaches offer promise as methods to quantify this exposure potential and the variability that exists, but should be validated with a robust monitoring dataset. This presentation is second in a two-part study that used pesticide residues monitored in five tile drained fields to evaluate the predictive capabilities of two pesticide transport models, the Root Zone Water Quality Model Version 2 ( RZWQM2) and a customized version of the Soil and Water Assessment Tool (SWAT). The parameterization and the physical process implementation of the two models will be described and compared. Results of uncalibrated and calibrated simulations of the two models at each of the five sites studies will be compared and overall model performance evaluated. The long term objective of this is work is to establish a modeling approach that can be used to evaluate the tile drain contributions of pesticides to surface receiving waters at the watershed scale.<br/>

Evaluation of model simulation of pesticide transport through subsurface tile drains

254th National Meeting (2017)

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