Toward Improving the Performance of SWEEP in Simulating Wind Erosion.

The Single-event Wind Erosion Evaluation Program (SWEEP), which is the erosion submodel of the Wind Erosion Prediction System (WEPS), was released in 2007. There are few studies that have evaluated SWEEP in simulating soil loss and no studies that have compared the performance of SWEEP in simulating soil and PM10 (particulate matter ≤10µm in diameter) loss from contrasting tillage systems under high winds. This study was designed to test SWEEP under conventional and undercutter tillage employed during the summer fallow phase of a wheat-fallow rotation in eastern Washington. Soil and PM10 loss and soil surface characteristics in adjacent tillage plots were measured during 2005 and 2006. Soil and PM10 loss were respectively up to 65 and 70% greater for conventional tillage than for undercutter tillage. SWEEP did not simulate soil or PM10 loss from either tillage treatment in response to high winds observed over the two years of this study. The reason for this observation is unclear due to the number of parameters and interaction of these parameters as constituted in SWEEP. One possible reason is overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion. Although many parameters are involved in the estimation of the threshold friction velocity, the internal empirical coefficients and equations in SWEEP may also affect the simulation. Empirical coefficients and equations could be adjusted via calibration to better represent wind erosion processes in eastern Washington. Uncertainty analysis is also another mechanism to bridge the gap in providing reliable model simulations.