Simulation of non-point source pollution with HSPF for the Chaida River Watershed of Lake Dianchi Basin

The analysis of non-point source pollution in watershed scale has been increasingly emphasized in recent years. HSPF (Hydrological Simulation Program - FORTRAN), included within the BASINS 3.0 (Better Assessment Science Integrating point and Nonpoint Sources) system, is a model which(that) has been developed to meet such assessment need. In this study, the Chaida River Watershed as the representative area of Lake Dianchi Basin was divided into three sub-watersheds and classified with seven kinds of land types with the tools of BASINS 3.0 system. According to sensitivity analysis and adjustment of HSPF model parameters, the hydrological and water quality process of the Chaida River Watershed were calibrated and validated by comparing simulated and observed scenarios in 1988 and 1989. Total loadings and non-point source pollution loadings of suspended solid (SS), total nitrogen (TN), total phosphorus (TP) in the watershed were calculated. The results showed that about 85% of SS, 1/3 TN and 1/4 TP were provided by non-point source pollution. Moreover, Decreasing 50% fertilizer utilization in the cropland could reduce 7% of the loadings in TN and TP and reclaiming 1/4 cropland and 2/3 uncultivated land to forest land could diminish over 10% of the loading of SS and a small quantity of TN and TP, which indicated the effectiveness of such measures to minimize the non-point source pollution in the watershed.