APPLICATION OF WEPP AND GIS-GRASS TO A SMALL WATERSHED IN INDIANA

Geographic information systems (GIS) are well-structured databases for handling large quantities of spatially varied data within a watershed . Linking of a GIS with a spatially, physically-bared, deterministic h ydrologic model such as the USDA-Water Erosion Prediction Project (WEP P) offers many advantages. The USDA-Water Erosion Prediction Project ( WEPP) model is a new computer program based on the fundamentals of hyd rology, soil physics, plant science, hydraulics, and erosion mechanics . The WEPP model provides several major advantages over existing hydro logic and erosion models;for example, it reflects the effects of soil surface conditions due to agricultural, range, and forestry practices on storm runoff and erosion. Furthermore, it models spatial and tempor al variability of the factors affecting the watershed hydrologic and e rosion regime. The WEPP model requires hydrometeorological, soil, topo graphy, and land-use data. The Geographical Resources Analysis Support System (GRASS) GIS was used to obtain many of the needed input parame ters. The WEPP model was evaluated on a watershed in the Indian Pine N atural Resources Field Station near West Lafayette, Indiana. The model -predicted storm runoff was compared with measured values. The results indicate that GRASS-GIS technology is a powerful tool and can he used to parameterize a complex hydrologic model such as WEPP? The results also indicate that using GRASS-GIS maps to recognize watershed configu rations and representative hillslopes improved the model's ability to predict storm runoff.