Simulation Study On Runoff And Non-point Source Pollution In Data-scarce Basins

Qingyi River is the largest tributary of Ying River,of which about 67%in Xuchang territory,mainly responsible for flood,drainage,sewage along the river area and an important function of urban landscape water in Xuchang,water pollution is serious in the river.In recent years,the comprehensive improvement of water environment mainly focused on the study of point source control of industrial wastewater and urban domestic sewage discharge in the Qingyi River basin,but ignored the influence of water quality at the non-point source pollution.Therefore,the paper focused on the non-point source pollution in Qingyi River,to provide scientific basis for the overall improvement and functional recovery of water environment quality in Qingyi River.Taking the Qingyi River as an example,the runoff and non-point source pollution model in data-scarce basins was constructed.The flow of the Qingyi River basin with lack of measured runoff data was calculated by using the above basin of Huangqiao hydrological station in Ying River as the model study area,on this basis,non-point source pollution in Qingyi River basin was simulated,the spatial and temporal distribution of non-point source pollution was analyzed.The key areas of non-point source pollution were identified,based on the analysis of pollution contribution rate,the prevention and control measures of non-point source pollution were given,which provided reference for the control and management of non-point source pollution.The main conclusions are as follows:(1)According to terrain,soil,land use and meteorological data,A basic database of SWAT models applied to the Ying River basin(above to Huangqiao hydrological station)is established.Extracted river network of basin based on the digital elevation model(DEM),the basin was divided into 37 subbasins.By loading land use,soil type and slope,the basin was divided into 349 hydrological response units(HRUs).(2)The calibrated Yinghe River basin model was applied to the Qingyi River basin by using the model parameter transplantation method.The relative error(Re),the coefficient of determination(R2)and Nash-suttcliffe(Ens)of simulation results in 1964-1973 were 6.025%,0.856 and 0.841 respectively at the Sanliqiao hydrological station in Qingyi River basin.The simulated value and measured value had a good fit degree.The model can be used to calculate the monthly flow of the Qingyi River basin in 2001-2013.(3)The temporal and spatial distribution of runoff and non-point source pollution load in the basin was analyzed from two aspects of interannual and annual.On the time scale,interannual variation of runoff and non-point source pollution load is wet year>normal precipitation year>dry year.Runoff and output of non-point source pollution load in annual were mainly concentrated in flood season.On the spatial scale,the annual of runoff and non-point source pollution load are mainly concentrated in the Xuchang section of Qingyi River basin at a wet year,and mainly concentrated in the lower reaches of the basin Linying County and Yanling County at a normal precipitation year and a dry year.(4)By calculating the concentration of TN and TP of non-point source in Qingyi River basin,the key areas of non-point source total nitrogen pollution were mainly concentrated in Xuchang County and Changge County.The contribution rate of TN and TP of non-point source was analyzed from two aspects of basin tributary water system and pollution sources.The results found that the contribution rate of nitrogen and phosphorus of non-point source was the highest in Xiaoni River system.In addition to natural factors,the contribution of chemical fertilizers to Total Nitrogen of non-point source was the highest among the four factors of non-point source,and the contribution rate of livestock and poultry breeding to Total Phosphorus of non-point source was the highest.The paper combined with the characteristics of the basin itself and analyzed results of contribution rate of non-point source pollution to make recommendations for prevention and control measures of non-point source pollution in Qingyi River basin.