SWAT-based Simulation On Non-point Source Pollution In The Upstream Watershed Of Tangpu Reservoir

The contradiction between supply and demand of water resources is increasingly outstanding,become one of the strategic issues of the world.Non-point source pollution has become the main factor of water environment deterioration and eutrophication,controlling non-point source pollution is of great importance to improve the water environment.As the drinking water source of Shaoxing region,Tangpu reservoir serves for nearly 2 million people in Shaoxing city,Shangyu city and Cixi city.It is very significant to analyze and calculate the potential non-point source pollution for protecting the water quality of Tangpu Reservoir.SWAT model developed by USDA Agricultural Research Service(ARS)was used to estimate the non-point source pollution.The main research content is as follows:(1)The simulation was used to involve geographic information data of landform,landuse,soil type,hydrology and meteorology of the basin,these data were divided into the attribute and the spatial ones,and it prepared well for the establishment of database applicable to SWAT model based on ArcGIS in this region.Then using ArcGIS and SWAT watershed delineator to devide the watershed into 27 subbasins based on DEM,at the same time,the digital river network was defined and subbasin parameters were calculated.By overlaying the landuse,soil type and slope classes map,study area was divided 288 hydrological response units(HRUs).(2)Monthly data series of 2002-2008 were used to calibrate correlative parameters of the runoff,sediment and nutrient load simulation.And the measured monthly data series of 2009-2011 were used to validate the model.Using relative error(RE),the determination coefficient(R2),Nash-suttcliffe simulation efficiency coefficient(Ens)to evaluate the applicability of the model,Results show that the simulated values were almost equal to the measured values.In result,it is suitable for using SWAT to model the non-point source pollution in Tangpu reservoir basin.and spatial variation of the basin non-point source pollution.On the time scale,there was a concentration of non-point source pollution in flood season.On spatial scales,the key source area to agricultural non-point source pollution was focused on the rival south valley,Wang yuan,Gulai,Wangtan,etc.(4)The influence on nutrients of varying main landuse types was studied.Generally,the proportion of cultivated land is the largest,followed by the urban land,pollution load of forest land and orchard was smaller.Different scenarios were designed to simulate the influence on sediment and nutrients of varying fertilization.After the above analysis,I ended the article by putting forward some suggestions on controlling the non-point source pollution of Tangpu reservoir watershed according to the basin characteristics and the simulation results of this study.