Simulation Study Of The Water Environment In Beijing-Tianjin-Hebei Region Based On The SWAT Model

Water resource is an indispensable key element of production,life and economic development in today's society.With the development of human society and the acceleration of urbanization,water pollution has become a bottleneck that affects human life and restricts economic development.In order to predict the changes of the water environment quality under different water pollution prevention measures,it is of great practical significance to use the water environment model to simulate and describe the water environment quality of the basin to understand its temporal and spatial changes.Distributed surface water environment model has become an important tool for auxiliaring water environment simulation research since it was proposed,and it has important significance for the study of water quality change law.SWAT?Soil and Water Assessment Tool?model,as a representative of distributed models,is widely used in river basin runoff,pollutant migration and transformation simulation,and underlying surface scenario change analysis.According to the geographical location,urban functions and industrial chain relationship of Beijing,Tianjin and Hebei province,China has put forward the Beijing-Tianjin-Hebei coordinated development strategy,which aims to promote regional division of labor,optimize industrial layout,and achieve economic development on the basis of protecting the ecological environment.It is a major national strategy to promote the harmonious development of population and environment,realize regional industrial complementarity,and drive the economic growth of the whole region.As a basic natural resource and economic resource,water of Beijing-Tianjin-Hebei region has been polluted to varying degrees,prevention and control of water pollution has become an important strategic work in this region.This article taked the overlapping part of Beijing-Tianjin-Hebei region and the Haihe River basin as the study area,addressing water pollution problems in the study area,three aspects of research have been carried out.First of all,basic data of the research area have been collected to understand the overall situation of the research area,and"3S"?GIS,GPS,RS?technology was used to establish the pollution source database of the study area.Secondly,the SWAT model was used to simulate the ammonia nitrogen?NH3-N?and total phosphorus?TP?pollution load of each sub-basins in the study area,and the export coefficient model combined with the one-dimensional water quality model was used to simulate the COD pollution load of each sub-basins in the study area.Finally,a spatial analysis of the pollution load of the study area was carried out,and the established SWAT surface water environment model and export coefficient model were used to predict and evaluate the pollution load reduction and response of typical regional water pollution prevention and control measures.The main research results are as follows:1.Through the collection,extraction and data integration of environmental statistical data,a point source pollution database of Beijing-Tianjin-Hebei region was constructed.The rural population pollution load,non-scale livestock and poultry farming pollution load,and agricultural fertilization obtained from districts and counties statistical yearbooks of Beijing-Tianjin-Hebei region were redistributed to each sub-basins by area weighting to construct a non-point source pollution database of Beijing-Tianjin-Hebei region.2.Water quality simulation of 41 monitoring sections have been completed,the relative error of the simulation results of NH3-N and TP pollution load did not exceed60%,and the relative error of the simulation results of COD pollution load for 37sections were less than 30%.The simulation results show that the pollution levels of NH3-N,TP,and COD in the study area are generally higher in the south and lower in the north,higher in the plains and lower in the mountain areas.NH₃-N pollution is most serious in Shijiazhuang urban area,with a pollution load intensity of about 300kg/km2·a,followed by Beijing and Tianjin,with a pollution load intensity of about18.62?58.55 kg/km²·a;TP pollution is most serious in Tangshan,Baoding,and Cangzhou,the pollution load intensity is about 0.61?1.84 kg/km2·a,followed by Beijing and Tianjin,about 0.04?0.12 kg/km²·a;COD pollution is most serious at the junction of Chengde and Tangshan,urban area of Beijing and Tianjin,and Langfang,the pollution load intensity is about 923.85?9,492.78 kg/km²·a.Among them,NH₃-N and COD are mainly discharged from point source pollution,while the Luanhe River and North Canal River basins are mainly discharged from large-scale livestock and poultry farming.The river basins of Yongding River,Daqing River,Ziya River and South Canal River are mainly discharged by urban domestic sewage;non-point sources as the main source of TP pollution,agricultural fertilization is the main source of phosphorus pollution.In the middle and lower reaches of each river basins,point sources of phosphorus pollutants are also one of the main sources of TP.3.This article taked the Ziya River basin as the testy area,the watershed pollution prevention and control measures scenarios were predicted and the burden reduction response evaluation was carried out.The research results showed that the50%topsoil fertilization rate combined with 30%point source reduction is the most suitable pollution prevention plan.