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Title: Evaluation of the SWEEP model during high winds on the Columbia Plateau

item Sharratt, Brenton

Submitted to: Earth Surface Processes and Landforms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2009
Publication Date: 9/9/2009
Citation: Feng, G., Sharratt, B.S. 2009. Evaluation of the SWEEP model during high winds on the Columbia Plateau. Earth Surf. Process. Landforms 34, 1461–1468.

Interpretive Summary: The Single-event Wind Erosion Evaluation Program (SWEEP) was released by the USDA Agricultural Research Service in 2007. Since this model will be used by the USDA in conservation programs and for identifying lands that are erodible by wind, testing the model under a wide range of environmental conditions is vital to improving its prediction capability. We found that the model did not predict erosion from loess soil managed using conventional or conservation tillage over two years in eastern Washington. The model may overestimate the threshold velocity required to initiate movement of loess soil. Although many soil and crop parameters are involved in the estimation of threshold velocity, empirical coefficients and equations in the model derived for coarse-textured soils may also affect its performance. USDA-ARS soil scientists or engineers can improve model performance through calibration of model parameters or by conducting further laboratory studies using loess soil to better define the coefficients and empirical equations in the model.

Technical Abstract: A standalone version of the WEPS erosion submodel, the Single-event Wind Erosion Evaluation Program (SWEEP), was released in 2007. A limited number of studies have evaluated SWEEP in simulating soil loss under high winds. The objective of this study was to test SWEEP under conventional and undercutter tillage that was imposed during the summer fallow phase of a winter wheat-summer fallow rotation within the Columbia Plateau. Instrumentation to measure soil and PM10 (particulate matter less than or equal to 10 µm in diameter regulated as an air pollutant) was established in adjacent fields managed using conventional and undercutter tillage during summer fallow in 2005 and 2006. While the tillage treatments created different soil surface conditions, SWEEP failed to simulate any difference in soil loss between conventional and undercutter tillage. In fact, the model simulated zero erosion for all high wind events observed over the two years. The reason for the lack of simulated erosion is complex because of the number of parameters and interaction of these parameters on erosion processes. A possible cause might be overestimation of the threshold friction velocity in SWEEP since friction velocity must exceed the threshold to initiate erosion. Although many parameters are involved in estimating threshold velocity, internal empirical coefficients and equations may affect the simulation. Calibration methods might be useful in adjusting the internal coefficients and empirical equations. Additionally, the lack of uncertainty analysis is an important gap in providing reliable output from this model.