Water erosion prediction project (WEPP): development history, model capabilities, and future enhancements

ABSTRACT. The Water Erosion Prediction Project (WEPP) was initiated in August 1985 to develop new‐generation water erosion prediction technology for use by federal action agencies involved in soil and water conservation and environmental planning and assessment. Developed by the USDA‐ARS as a replacement for empirically based erosion prediction technologies, the WEPP model simulates many of the physical processes important in soil erosion, including infiltration, runoff, raindrop and flow detachment, sediment transport, deposition, plant growth, and residue decomposition. The WEPP project included an extensive field experimental program conducted on cropland, rangeland, and disturbed forest sites to obtain data required to parameterize and test the model. A large team effort at numerous research locations, ARS laboratories, and cooperating land‐grant universities was needed to develop this state‐of‐the‐art simulation model. WEPP project participants met frequently to coordinate their efforts. The WEPP model can be used for common hillslope applications or on small watersheds. Because it is physically based, the model has been successfully used in the evaluation of important natural resources issues throughout the U.S. and in many other countries. Upgrades to the modeling system since the 1995 DOS‐based release include Microsoft Windows operating system graphical interfaces, web‐based interfaces, and integration with Geographic Information Systems. Improvements have been made to the watershed channel and impoundment components, the CLIGEN weather generator, the daily water balance and evapotranspiration routines, and the prediction of subsurface lateral flow along low‐permeability soil layers. A combined wind and water erosion prediction system with easily accessible databases and a common interface is planned for the future