Geographic information system-assisted dynamic modeling of soil erosion and hydrologic processes at a watershed scale

A Geographic Information System (GIS)-assisted simulation model of the dynamic processes of soil erosion and hydrology of a watershed has been developed, called Predicting Catchment Runoff and Soil Erosion for Sustainability (PCARES). PCARES is a physical model that can simulate runoff and soil erosion of a catchment area during a rainfall event. The basic inputs to run the model include raster maps of the elevation, soil, and land use pattern of the catchment, and a time series on the amount of rainfall. Important outputs include a map of source erosion and runoff discharge and sediment yield at the outlet of a catchment area. For validation of the model, the Mapawa catchment area in Bukidnon, Southern Philippines was parameterized in terms of the PCARES' input requirements to assess the impact of land surface-cover treatments on water quantity and quality. The treatments were: (T) bare surface, (2) current vegetation with minimal soil conservation measures and (3) forest cover. The bare surface gave the highest water and sediment discharge rates while the forest cover gave the least runoff with almost no sediment load. The results demonstrate both the power of the simulation model and the enormous positive effect of surface cover in managing soil erosion and runoff in a watershed. The model may also be useful in predicting the impacts on conservation of research and development projects even before they are carried out in the watershed.