The Water Erosion Prediction Project (WEPP) model is a process-based, continuous simulation, computer model for determining the effects of climate, soil, topography, cropping, land management, and conservation practices on soil erosion by water. Developed by the United States Department of Agriculture (USDA) since 1985, and first publicly released in 1995, WEPP has been applied within the United States and in numerous countries throughout the world. The USDA Forest Service (FS) has extensively used WEPP, particularly for wildfire assessments and remediation planning, and has developed their own targeted web-based interfaces and databases. Since 2013, the USDA-Agricultural Research Service (ARS) has been working cooperatively with the USDA-Natural Resources Conservation Service (NRCS) on a project to implement WEPP in over 2000 county field offices for soil conservation planning activities. ![]()
This work has involved development of new web-based interfaces for hillslope profiles (Figure 1) and field-sized watersheds, modifications to the WEPP science model code, extensive database expansion and testing for climates, crops, operations, and soil conservation practices, and evaluation of WEPP predictions compared to current erosion prediction technologies. In addition to ARS and NRCS, other cooperators on this implementation project include Purdue University, the University of Idaho, and Colorado State University. Climatic inputs that drive the WEPP model have been updated to use precipitation data from over 2700 weather stations in the U.S. with forty years of temporally consistent information from 1974-2013. WEPP simulates the physical processes important in water erosion caused by raindrop impact and overland flow. If rainfall, snowmelt, or irrigation occur on a simulation day, the model determines the amount of infiltration and whether any runoff occurs. If runoff is predicted to occur, the total amount and the peak runoff rate are determined, as well as the effective rainfall intensity. Rill erosion is computed as a function of excess flow shear stress, while interrill (sheet) erosion is a function of rainfall intensity and runoff rate. Soil detachment or deposition is determined at a minimum of 100 equally spaced points down a slope profile, as is sediment leaving the end of the profile. If run in a watershed configuration, water and sediment from adjacent hillslopes flows into channels, where sediment transport, more detachment, or deposition may be predicted. WEPP tracks live plant biomass, dead plant residue, live and dead roots, soil roughness, consolidation, and moisture conditions on a daily basis. Soil detachment, sediment deposition, and sediment delivery are tracked spatially and temporally, and summarized at the end of the simulation period. The model accounts for the effects of numerous complicated interactions through long-term (100+ years) simulations. This presentation will cover the current status of WEPP and new NRCS interfaces and databases.
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