Continuous simulation of water and soil erosion in a small watershed of the Loess Plateau with a distributed model

A physically based distributed hydrological model (THIHMS-SW, TsingHua Integrated Hydrological Modeling System-for Small Watershed) was developed and applied to a 187 km(2) watershed in the severe soil erosion region of the Loess Plateau. In the model, calculations of water and sediment transport were coupled in each grid, and the modeling of water and soil conservation measures, especially the silt-trapping dam, was also included. Continuous simulation for a period of eight years undisturbed by human activities was carried out and the results indicate that the model worked well in terms of estimating water/sediment peak discharge, time to peak, and total volume at different locations. Continuous simulation for three years after the installation of hundreds of silt-trapping dams was also carried out and fairly good results were obtained. The model is physically based and can be used in water resources planning, land use management, flood control, as well as water and soil conservation planning in small watersheds.