Validation of the Wind Erosion Equation (WEQ) for discrete periods

In the United States, the USDA Natural Resources Conservation Service (NRCS) is the primary agency charged with the task of reducing wind erosion associated with production agriculture. The NRCS has used the Wind Erosion Equation (WEQ) (Woodruff and Siddoway, 1965) to assess the effects of field management on the potential for wind erosion for the last two and a half decades. The WEQ uses inputs of soil erodibility, ridge roughness, locally calibrated climatic factors, field length, and vegetative cover to predict the potential annual wind erosion for a given field and set of management variables. By using this model, the NRCS is able to direct producers toward crop management systems that effectively reduce erosion. Wind erosion modeling efforts by the USDA Agricultural Research Service (ARS) over the last decade have necessitated the collection of several large bodies of wind erosion and weather data from many diverse locations in the United States. This effort has been facilitated by the development of technology and equipment that have enabled the measurement of wind erosion losses on storm event basis (Fryrear, 1986; Stout and Zobeck, 1996). The availability of field measurements has improved the description of erosion losses across a field (Stout, 1990) and also permits the validation of wind erosion models. We tested WEQ against much of the aforementioned body of data in order to determine the accuracy of its predictions. The Global Change and Terrestrial Ecosystems Soil Erosion Network (GCTESEN) has recently conducted a model validation exercise for water erosion models (See September October 1996, J. Soil & Water Conserv.). Several models also are available to estimate wind erosion losses, but few studies have compared the output from these models with field-measured data. In this study, as part of a GCTE-SEN project, we evaluate how well predictions of erosion made with a commonly used model compare with data collected from eroding fields. We also investigate appropriate factors that may be changed to calibrate WEQ for local climate and soil conditions.