WEPP

WEPP, the Water Erosion Prediction Project, is a process-based erosion-modeling framework designed to simulate rainfall-induced soil erosion, surface runoff, and sediment transport on hillslopes and small watersheds. It integrates hydrology, soil erosion mechanics, and sediment routing to estimate soil loss and sediment yield under diverse climate, soil properties, topography, and land-management practices. WEPP was developed in the United States during the 1990s through collaboration among the USDA Agricultural Research Service and university partners, with the aim of providing a physically based alternative to empirical models such as the Universal Soil Loss Equation.

The model is modular, comprising components for hillslope erosion, watershed routing, and management scenarios. The hillslope module computes rainfall-runoff generation, infiltration (using infiltration models such as Green–Ampt), overland flow, detachment by raindrop impact, and transport and deposition of sediment. The watershed module routes sediment through channels to outlet points. Management inputs simulate crops, residue cover, tillage, and practices intended to reduce erosion. Time steps can be event-based or daily, and the model uses standard soil properties, topography, and climatic data to drive simulations.

Inputs required include climate data, soil properties, slope characteristics, and land-management parameters. WEPP can be used with graphical interfaces and GIS tools, such as WEPP-GIS, to prepare inputs and visualize outputs. Outputs typically include soil loss, runoff depth, sediment yield, and potential nutrient losses, aiding soil conservation planning and evaluation of practices like cover crops, residue management, and contouring. Limitations include data demands, calibration needs, and the requirement for technical understanding to ensure reliable results.