Assessing regional impacts of Conservation Reserve Program-type grass buffer strips on sediment load reduction from cultivated lands

A methodology of determining regional estimates of Conservation Reserve Program (CRP) areas required to achieve a given percentage reduction of localized agricultural sediment yield is introduced. Using South Dakota as a test domain, a collection of regional-scale databases was used to compile a statewide erosion vulnerability map based on Universal Soil Loss Equation (USLE) factors. This was then arranged into climate, erosion risk, soil and topographic zones. Statistical procedures were then employed to extract predominant input values required for the U.S. Department of Agriculture (USDA) Water Erosion Prediction Project (WEPP) model applicable to each of these zones. WEPP simulations using these inputs provided estimates of grass buffer strip areas required to achieve targeted percentage reductions of sediment yield in each of these zones. The response of each of these zones towards employment of grass buffer was found to vary considerably. Comparison with small-scale field studies suggest that the WEPP model can be used to measure efficiency of grass buffer strips in different zones. This approach demonstrates how regional analyses using factor-based erosion models can be combined effectively with process-based field-scale erosion models to provide viable estimates of sediment reduction due to adoption of CRP-type grass buffer strip practices.