Abstract: Soil erosion was very serious in the Guishui area of Guanting reservoir. In order to control the non-point source (NPS) pollution of soil loss there, a distributed soil erosion and sediment transport sub-model with less parameters and more convenient application was built in this paper, which was composed of the USLE model and the sediment transport model. Firstly, USLE was used to calculate soil erosion after suitable calculation formulae of its factors were selected. And then the watershed was generalized into river network, we applied the relation between S-curve and pollutant-collecting area coefficient we had established into the solution of one-dimensional water quality transportation equation gained from Laplace transform and inverse Laplace transform, and derived the distributed sediment transport model. Finally, relied on DEM, this paper made research on the model application in Guishui watershed by picking up geographical information from the soil map and land-use map of Guishui watershed. Application results indicated that this model can not only be used to make research on the sediment pollution resulting from NPS pollution, but also on the spatial distribution of soil erosion, offering scientific foundation for realizing best agricultural management in this watershed. The soil loss in Guishui watershed mainly comes from the mountain and hill with large slope and low vegetation coverage, therefore, the key for controlling the soil loss shall be taken on the mountain and hill in this watershed.

Key words: nonpoint source pollution, distributed model;, GIS, Guanting Reservoir, Guishui River