Study On Applicability Of Swat In Huangshui River Basin

Distributed hydrological model—Soil and Water Assessment Tool(SWAT) is applied to simulate water recycle process, soil erosion process, and the transfer process of polluting materials in Huangshui River Basin. So we can make a quantitative assessment on water yield,sediment yield and pollutant yield of the basin as well as their spatio-temporal distribution. And with the help of SWAT, we can unify the continuous change of water quantity with the evolvement of associated water quality, so the comprehensive assessment on water quantity and quality of the basin would be carried out.Firstly the network of rivers and subbasin are identified from DEM of the basin. Then the soil-type and landuse are reclassified, the data base of soils is set up. Parameters of the model were calibrated and the model is tested by observed data and the critical parameters are tested by a sensitive analysis. In consideration that the study area is about 15600 km~2 large, the goodness of fit of the model is satisfied.The simulated outcome by the calibrated model shows that over 70 percent precipitation and 65 percent runoff of the basin focus on the upperreaches of Xining station, while 80 percent sediment yield and 70 percent non-point source pollutants come from the watershed area which locate between Xining station and Minhe station. The difference of water yield, sediment yield and loadings of non-point source pollutants in different hydrologic years is dramatic. The sediment and loadings of non-point source pollutants caused by rainstorm focus on flood season especially in July. Each land cover represented in the model yields different results. Tilth contributes the most of nitrate and soluble phosphorus yield. RNGB (the mountain range brush) and SWRN (the mountain range grasses) contributes the most sediment yield accompanying the highest ORG_N and SED_P yield. Finally the model is applied to make comprehensive assessment on the basin's water quantity and quality. The outcome showed that the water pollution of the Huangshui River is very serious, which was covered in some degree by the river length evaluating method that didn't consider of the integration of water quantity and quality. The results indicate that SWAT model can be applied to comprehensive evaluation analysis of water resources in Huangshui River Basin.