Research On The Temporal And Spatial Distribution Characteristics Of Non-point Source Pollution In The Main Stream Of Burhatong River Based On SWAT Model

Non-point source pollution is one of the main types of pollution that affects the water environment.With the further control of point source pollution,non-point source pollution as the main source of pollution seriously affects the quality of the water environment.This is the most significant aspect of global water environment pollution..Domestically,one of the most prominent reasons for the deterioration of water quality in natural waters is non-point source pollution.With the promotion of water environment management and pollution control,my country’s non-point source pollution research has developed rapidly in the past decade,and has become an important global research and innovation base.The research on non-point source pollution focuses on the application of the model,and the domestic SWAT model is used to study the non-point source pollution in the watershed,and has achieved certain scientific research results.By constructing the SWAT model of the main stream of Burhatong River in the middle reaches of Tumen River,this paper establishes a model suitable for this study area,simulates and analyzes the temporal and spatial distribution characteristics of non-point source pollution in the main stream of Burhatong River,and analyzes the non-point source pollution of the main stream of Burhatong River Structure and key land-use types to simulate changes in non-point source pollution under land-use changes.The main results of this study are as follows:(1)The SWAT-CUP was used to calibrate and verify the simulation results.Among them,R2=0.71,NSE=0.63,regular period runoff R2=0.82,NSE=0.74;periodical total phosphorus R2=0.79,NSE=0.68,Verification period R2=0.97,NSE=0.96.(2)Time-varying characteristics of total phosphorus in non-point source pollution:The total phosphorus loss load varies greatly during the year,with a maximum value of 48.59 tons/month,a minimum value of 0.04 tons/month,and an average value of 8.43 tons/month.Total phosphorus loss has obvious seasonal variation and has a strong correlation with rainfall.Winter is a trough period caused by non-point source pollution.The average total phosphorus loss in four years in winter accounts for 5%of the average loss in four years;the total phosphorus loss load in spring is basically the same as the total phosphorus loss load in autumn;summer is non-point source pollution During the peak period,the total phosphorus loss load in the summer of 2013-2015 accounted for more than 60%of the whole year.Rainfall is the dominant factor driving the loss of non-point source pollutants.(3)Spatial variation characteristics of total phosphorus in non-point source pollution:The annual average TP load is basically distributed along the channel,the main channel load is greater than the tributary channel,and the downstream load is significantly greater than the upstream load.The annual average total phosphorus(TP)load intensity is between 0.035kg/ha and 1.17kg/ha,and the average value is 0.91kg/ha.There is a large difference in the total phosphorus load intensity between different sub-basins.The total downstream load is significantly greater than the upstream load because the upstream load will be lost during the transfer process,but most of it still exists in the water body.In addition,the basin itself will generate new loads.This accumulation makes the downstream load The load is increasing,so the TP load is the most at the total outlet of the basin.Most of the sub-basins with serious pollution load in the watershed are urban land and cultivated land,which are greatly affected by the output of urban non-point source and farmland non-point source.Land use type is the main factor affecting the spatial distribution of non-point source pollution TP.The spatial distribution of rainfall and the spatial distribution of TP load are basically consistent.(4)The total phosphorus output intensity of different land-use types in the main stream of Burhatong River is between 0.89-11.29 kg/ha,and the land use types with the largest total phosphorus output are farmland,forest land and urban land,accounting for Burha respectively 61.73%of the total phosphorus output in the Tonghe River Basin,25.7%and 12.45%.Farmland non-point source and decentralized livestock and poultry farming are the biggest contributors to TP load in the watershed.(5)Simulated the impact of three kinds of land use changes on non-point source pollution load.It was found that after changing urban land to forest land,cultivated land to wetland and cultivated land to forest land,the total phosphorus(TP)in the watershed showed a certain range The reductions were reduced by 20.52%,24.39%and 34.33%respectively.Finally,according to the actual situation of the main stream of Burhatong River,combining three simulation results,scientific management measures are proposed.