Pesticides move to surface water via various pathways including surface runoff, spray drift and subsurface flow. Surface runoff is often considered as the most important transport route in many areas. However, in some watersheds, spray drift has been shown to be a significant contributor. Little is known about the relative contributions of surface runoff and spray drift in agricultural watersheds. This study attempts to develop a modeling framework to address the contribution of spray drift to the total loadings of pesticides in receiving water bodies.  The modeling framework will consist of models for simulating spray drift, surface and subsurface runoff and environmental fate processes in receiving water.  Monitoring data collected from daily samples were used for model evaluation. Preliminary approach using the AgDRIFT  and the Variable Volume Water Body Model  (VVWM) showed good agreement between model predicted concentrations for drift events and less so for runoff events. To improve the simulation performance, a watershed approach integrating the AgDRIFT model with the Soil and Water Assessment model (SWAT) is under development.  Once validated, the modeling framework could be a valuable tool to the decision making in pesticide risk management and mitigation such as where and what types of best management practices to implement in a watershed.<br/>

Modeling spray drift and runoff related inputs of pesticides to receiving water

253rd National Meeting (2017)

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