Management-Oriented Sensitivity Analysis for Pesticide Transport in Watershed-Scale Water Quality Modeling.

The Soil and Water Assessment Tool (SWAT) was calibrated for hydrology conditions in an agricultural watershed of Orestimba Creek, California, and applied to simulate fate and transport of two organophosphate pesticides chlorpyrifos and diazinon. The model showed capability in evaluating pesticide fate and transport processes in agricultural fields and in stream network. Management-oriented sensitivity analysis was conducted by applied stochastic SWAT simulations for pesticide distribution. Results of sensitivity analysis identified the governing processes in pesticide outputs as surface runoff, soil erosion, and sedimentation in the study area. By incorporating sensitive parameters in pesticide transport simulation, effects of structural best management practices (BMPs) in improving surface water quality were evaluated by SWAT modeling. The paper also recommends the conservation practices designed to reduce field yield and in-stream transport capacity of sediment, such as filter strip, grassed waterway, residue management, and tailwater pond to be implemented in agricultural lands of the Orestimba Creek watershed.