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

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 model uses inputs of soil texture. annual mean climate data, statistically derived wind energy apportionment tables, and field management options to predict soil loss on a management period and annual basis. 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. WEQ under-predicted the observed estimates of 11 of the 14 periods by as much as a factor of nine. For the three periods that WEQ over-predicted observed erosion estimates, the factor was less than 1.5. Across all sites and periods considered in this investigation, WEQ only predicted about 53% of the observed estimated erosion. Analysis of two average years at Big Spring, TX, indicated that WEQ could be locally calibrated by use of increased climatic (C') and soil erodibility (I) values as well as combinations of the two. (C) 2003 Elsevier Ltd. All rights reserved.