On the applicability of SWAT model to the non-point source pollution in the watershed of the three-gorge reservoir

This paper intends to study the applicability of SWAT model to the non-point Source pollution in the watershed of the Three-Gorge Reservoir.The so-called SWAT(Soil and Water Assessment Tool) model is a model we have developed in hoping to be applied and adapted to the macro-scale watershed,in the TGR area as a case study.The said model has been established under the support of the Geographic Information System(ArcGIS) as well as the spatial dataset such as DEM(digital elevation model),land-use map and so on.In our research,we have studied the data of hydrological and water quality in the TGR area from 2002 to 2008 for simulated calibration and validation.On the whole,our simulation proves to be successful,for the indicator ENS(Nash-Suttclife efficiency) for stream flow in most cases was above 0.9,whereas the ENS for sediment was from 0.46 to 0.9 though the ENS for nutrient in some individual cases was less than 0.36.We have also studied the correlation between the precipitation and the surface runoff,sediment load,nutrient load in the TGR area,too.The results of our simulated investigation have shown that the surface runoff and sediment load were both closely related with the precipitation,except that the peak of sediment load took place earlier than that of surface runoff in April or May occasionally.The reason for the sediment situation is perhaps that it is because of the large amounts of the soil loss caused by the tillage and precipitation activities during the season.As to the nutrient load,especially,the TP,the consequence seems also relevant to the sediment load in comparison with the surface runoff.And,finally,we have also analyzed the pollution loads generated by the different landuse types in the area.When we worked out the order of the average pollution load for different landuse situations,we have found that the most serious non-point sources of pollution are the crop fileds in the TGR area.So it is urgent to improve the cultivation measures and change the landuse types so as to reduce the pollution situation.Further studies of the pollutant loads per area of landuse types were also evaluated later,which prove the applicability of SWAT model to the pollution situation research in the TGR area.Thus,it can be concluded that the given model enjoys the scientific support for non-point pollution control in the area.