Validation of the Wind Erosion Equation (WEQ) for discrete periods and of the Wind Erosion Stochastic Simulator (WESS) for single events

The Wind Erosion Equation (WEQ) is currently used by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) to ensure compliance with government guidelines for soil loss from agricultural land. The Wind Erosion Stochastic Simulator (WESS) is a single event wind erosion model that is the core of the wind erosion submodel of the Environmental Policy Integrated Climate (EPIC) erosion model. In this study we compared estimates of wind erosion derived from the sums of field measurements at seven locations, two of which had multiple years of observations (a total of 14 periods of comparison), with the predictions of WEQ. We also compared estimates of wind erosion at multiple points in a field for 24 events at Big Spring, Texas with the predictions of WESS. Overall, WEQ predicted only 53% of the total observed erosion for the fourteen periods. WEQ underestimated 11f the 14 periods investigated. by as much as a factor of nine and of the three periods WEQ over-estimated, the maximum factor was less than 1.5. WESS under-predicted 9 events, accurately predicted 8 events, and over-predicted 7 events. WESS tends to under-estimate large magnitude storms and over-estimate very small magnitude storms, therefore, WESS would tend to under-estimate annual erosion.