WEPS uses a simulation model that integrates the specific factors of weather, crops, tillage, and soils to compute soil erosion and deposition. WEPS was developed to model and measure the horizontal and vertical movement of wind eroded soil as influenced by soil, climate and management conditions. Additionally, WEPS measures and models the loose material on crusted soils and the development of surface crust as influenced by soil texture, rainfall, tillage, and crop residues.
The WEPS structure has the following submodels; WEATHER, CROP, DECOMPOSITION, HYDROLOGY, SOIL, TILLAGE, and EROSION. A weather generator simulates daily weather to drive submodels which predict field surface conditions. These include soil, crop growth, decomposition, HYDROLOGY, and MANAGEMENT submodels. For WEATHER, a data vase was developed with more than 900 stations of monthly climatic wind statistics for each of 16 directions. A stochastic wind simulator was also developed.
For CROP, the EPIC model crop growth sections were incorporated. The HYDROLOGY submodel was developed which predicts soil water balance and soil surface wetness. An EROSION submodel predicts soil loss/deposition subhourly on days with wind erosion. Theoretical equations were developed for conservation of saltation and creep size aggregates in a control volume considering sources and sinks. SOIL and TILLAGE submodels incorporated theoretical equations.
Input data requirements include climate statistics, parameters for management, soil data, crop growth and decomposition parameters. Data output includes soil loss and deposition, including a suspension component, water balance, and crop biomass. The temporal scale is daily, but erosion calculations are sub-hourly. The spatial scale is approximately 640 acres.