Simulation Of Non-point Source Nitrogen And Phosphorus Load In Rongchang District Based On SWAT Model

Point source pollution has been well controlled and controlled,rather than point source pollution.Due to the wide sources,strong randomness,and responsible ingredients,it has become the number one issue in environmental governance.At present,the main way to study non-point source pollution is to use mathematical models to simulate the load of non-point sources.This article takes non-point source nitrogen and phosphorus pollution in Rongchang District of Chongqing as the research object,collects and organizes important local data of Qingliu River and Laixi River basin,combined with the DEM,land use,meteorology,water quality monitoring and other data of the river basin.Calculation and analysis of the spatial and temporal distribution characteristics of non-point source nitrogen and phosphorus pollution using geographic information system(GIS)and hydrological distributed model(SWAT),and verify the adaptability of SWAT model in Rongchang District;discuss the primary pollution sources and pollutants in the study area,as well as the impact of different land uses on non-point source nitrogen and phosphorus loads;summarize the research content and put forward effective countermeasures for water pollution prevention in Rongchang District.The main research results and conclusions of the paper are as follows:(1)The water quality fluctuation in Rongchang District is obviously affected by the season and precipitation.It is mainly affected by the concentration of total nitrogen and total phosphorus.In point source pollution,the total nitrogen discharge mainly comes from industrial wastewater discharge,and its discharge accounted for76.95%of the total;the total phosphorus discharge is approximately equal to that of urban and industrial.By estimating the contribution rates of TN and TP in point sources are 38.39%and 8.87%,and the contribution rates of TN and TP in non-point sources are 61.61%and 91.13%.The pollutants in Rongchang District mainly come from non-point sources.(2)The SWAT model has good applicability in this study area.When simulating runoff and nitrogen and phosphorus pollution loads,the verification period determination coefficient R~2 is 0.83,0.79,0.80,the Nash efficiency coefficient Ens is0.81,0.72,0.69,relative The error Re is within 20%.(3)The simulation results of the model’s non-point source nitrogen and phosphorus pollutant load in Rongchang District were calculated.The average annual emissions from 2011 to 2016 were 3136.469t/a and 746.972t/a,respectively.Among them,the total nitrogen load from 2014 to 2016 was 3166.28t,3153.06t,and 3100.71t,and the total phosphorus load was 760.36t,758385t,and 747.15t,respectively.(4)It is confirmed that the rainfall and runoff have a good correlation,and R2 is0.75,and the two are more consistent in the change trend.Annual precipitation,runoff,TN production,and TP production are significantly more in flood season than in non-flood season,and the proportion in the flood season is about 80.04%,78.70%,79.14%,79.87%,On the whole,the load of non-point sources TN and TP shows a certain seasonality.(5)Non-point source pollution is the primary type of pollution in each sub-basin.The use of chemical fertilizers in agriculture is the primary source of pollution that causes TN load pollution,while livestock and poultry farming is the source of pollution that generates more TP load.They accounted for 53.06%and 78.31%respectively.Propose pollution control and prevention suggestions for Rongchang District:source control,transmission control,Water quality improvement and international cooperation and exchange improvement.