WEPP and GLEAMS simulations of runoff and soil loss from grazed pasture in the southeastern United States

This study compared simulated values of surface runoff and erosion from two current erosion prediction technologies (WEPP and GLEAMS) to observed data for two grazing pressures on three pasture vegetation types (switchgrass, bermudagrass, and tall fescue) in the Tennessee Valley region of Alabama. Based on the results of statistical analysis for each forage type and grazing pressure, GLEAMS performed better than WEPP, although either model did not predict sediment loss within an acceptable level. Because it; was determined that grazing pressure had no significant impact on runoff and erosion from the experiment plots, the data for each forage were pooled over the same grazing pressure and the correlation between observed and simulated data were analyzed. This analysis showed that overall, predicted runoff values for both WEPP and GLEAMS had linear relationship to observed data. When sediment loss was analyzed, GLEAMS predicted value showed significant correlation with observed data, while WEPP predicted values did not. The results indicate that models may be use as management decision aids on pastures in the southeastern U.S., but more refinement to the models and available input data is necessary before predictions wilt be consistently accurate.