Simulation Of Non-Point Source Pollution In Qinhuangdao Area Based On SWAT Model

The seriousness of water pollution in today's society has been widely concerned at home and abroad.Water pollution problems are usually divided into point source pollution and non-point source pollution.In the case that point source pollution control ability is gradually improving and point source pollution is effectively managed,non-point source pollution has become the main source of water pollution.Especially in the 21 st century,China's agricultural non-point source pollution's impact on the eutrophication of water will further intensify,and water pollution cased by agricultural and rural development will become one of biggest challenges of China's sustainable development.There are many factors that affect the non-point source pollution.The land use/cover change is the key influencing factor of non-point source pollution.It affects the occurrence of non-point source pollution and the migration process of its nutrient by affecting runoff and sediment and then affect the nitrogen and phosphorus load of non-point source.Qinhuangdao,which is near the sea and has a rich water system belonging to the Luan River and Jidong coastal rivers,is relatively rich in water resource in North China.However,in recent years,the environment of water resources in this area has shown the trend of worsening pollution,and the safety of water environment is relatively low.Currently,the point source pollution of water environment has been controlled and solved to a degree,and damages of non-point source pollution have not fully demonstrated.But from the development point of view,it is necessary to study the non-point source pollution of the region,and provide the scientific basis for the prevention and control of non-point source pollution of the region.Therefore,based on the consideration of non-point source pollution,this paper discusses the effect of different land use patterns on non-point source nitrogen and phosphorus pollution in Qinhuangdao area.It mainly includes the following:(1)Based on the field investigation,the data collection and collation were carried out.According to the data of the main river basins,water quality monitoring data,hydrological site data,rainfall station data and weather station data etc.of Qinhuangdao area,the space of SWAT model was built by ArcGIS software Database and attribute database.(2)Based on the spatial data and attribute data,SWAT model was used to simulate runoff,sediment and the total nitrogen and total phosphorus load of non-point source pollution of Qinhuangdao area.The parameters of the runoff,sediment,total nitrogen and total phosphorus were obtained by parameter sensitivity analysis.The model parameters were calibrated and the validity and applicability of the model were validated.The model suitability evaluation index Re,R2 And Ens are within the required range of the SWAT model.(3)Based on the land use/cover data of Qinhuangdao area in 2000,2005,2010 and 2014,the land use/cover change of Qinhuangdao area was analyzed by spatial superposition analysis of temporal and spatial characteristics of land use/cover.(4)According to the land use pattern of four different periods,the area and proportion of land use types in each period were obtained,and SWAT model was used to add four different land use types respectively to study the runoff,sediment,non-point source total nitrogen and total phosphorus load.The effects of land use change on the spatial and temporal changes of runoff,sediment and the total nitrogen and total phosphorus load of non-point source pollution were analyzed.(5)By contrasting the temporal and spatial changes of total nitrogen,total phosphorus load of non-point source pollution,the spatiotemporal variation of the four scenarios was relatively consistent,indicating that runoff and sediment yield were key restrictive factors of total nitrogen phosphorus loading.When runoff is large,it carries more dissolved nitrogen and phosphorus elements;when the amount of sediment is large,its load of adsorption of nitrogen and phosphorus elements is large.Both of them increase the total nitrogen and phosphorus load.(6)The land use scenario was predicted by SWAT model.The nitrogen and phosphorus load of non-point source pollution under three land use scenarios were simulated by SWAT model.Based on the simulation results,three different prediction scenarios were used to analyze the different land use's spatiotemporal effects of nitrogen and phosphorus of non-point source pollution of Qinhuangdao region.