Study On Non-point Source Pollution In Beiru River Basin On SWAT Model

Under the background of rapid development of global economy and climate warming,water shortage and pollution have become the focus of scientists all over the world.Strong human activities affect the change of land usage types,the increase of construction land area and the reduction of forest land and cultivated land,and because of the extensive use of the agricultural production process,chemical fertilizers and pesticides,are increasing the non-point source pollution load in river basins.The increase of atmospheric temperature affects atmospheric precipitation patterns,and therefore affects the change of water environment.With the change of land use and climate conditions,the water ecological environment of Beiru River basin is destroyed.On the basis of Arc GIS10.1,SWAT2012 and remote sensing software,this thesis regards Beiru River as the research object,simulates non-point source pollution load from 2001 to 2015,and forecasts the trend of 2046-2064 basin non-point source pollution load by simulating the three climate modes of CMIP3,which aims to discuss the response to non-point source pollution land use and climate change,can provide the basis for the foundation management,administration and evaluation of ecosystem Agro-forestry ecosystem and the like.The main conclusions are as follows:(1)By analyzing sub division level in a river basin of Beiru River and considering the different sub basin divisions of runoff,sediment and nutrient load output results,we can determine to divide the Beiru River basin into 70 sub divisions.(2)By constructing the SWAT model which is suitable for the Beiru River and comparing simulated values and measured values in Dachen station from 2001 to2015,analyze the sensitivity parameter and adjust,Through the model calibration and verification,R2 and Ens have all reached the requirements of the model and the SWAT model has certain applicability in Beiru River.(3)By classifying and processing remote sensing image in 2001 and 2014 the thesis learns that the land usage types within basins are mainly land and farmland.Forest land and cultivated land area are 50.14% and 46.89% of the total area of 2001,and accounts for 49.23% and 41.62% of the total area of 2014.Compared with 2001,forest land and cultivated land area decrease and construction land and transportation land area increase in 2014.(4)Non-point source nitrogen load mainly dissolves nitrogen and phosphorus with absorption.(5)Based on land use map of 2001(L1)and 2014(L2),the paper simulates non-point source pollution from 2001 to 2015.The sediment and total phosphorus load of L1 and L2 are higher in flood season,and lower in dry season,and different in specific months.Under L1 and L2 total nitrogen and total phosphorus load spatial distribution patterns are basically the same,showed high in east and low in west,regions focus on non-point source pollution control in eastern.(6)Convection within the county district non point source pollution load for analysis available,the total amount of sediment and phosphorus loads Ruzhou,unit woodland area of sediment and phosphorus load up;SONGXIAN unit of arable land and sediment nitrogen phosphorus load up;the total amount of sediment and phosphorus load SONGXIAN minimum;Xiang Cheng Xian unit sediment and phosphorus loading lowest amount of arable land;Yu Zhou Shi unit woodland area of sediment and phosphorus load to a minimum.County district unit of cultivated area of the non-point source pollution load were higher than the unit load woodland area,indicating that the main source of non-point source pollution load of cultivated land in.Farmland shelter belts especially river,canal on the buffering forest have a good effect on reducing sediment and non-point source pollution load into the water,and the forest ecosystem can also achieve this effect.(7)SRES A2(high emissions),under the SRES A1B(emissions)and SRES B1(low emission)three scenarios,2046-2064 compared to 2001-2015,the overall runoff showed a decreasing trend,but the trend is not obvious.2046-2064 under three scenarios traffic in the inner diameter of the same trend,in July and August runoff is large,from December to February runoff is small.Water production under three scenarios spatial distribution pattern more consistent,both in the west and east.(8)Under the three scenarios sediment load changes stable from2046 to 2064 comparing from 2001 to 2015.Under three scenarios the change trend of sediment load is almost the same,both showing bigger in July and August and smaller from November to April.Under three scenarios the sediment yield is consistent,all showing high in east and low in west.(9)Overall,under A2 scenario total nitrogen load from 2046 to 2064 shows decreasing trend,under A1 B scenario the total nitrogen load is increasing,but the trend is not obvious;under B1 scenario total nitrogen load change is stable.In this three scenarios change trend is consistent,as total nitrogen load is bigger from May to August and smaller from October to February.Under the three scenarios the total nitrogen load shows high in east and low in west,which is consistent with the spatial distribution pattern of sediment yield in the basin.(10)Under A2,B1 and A1 B the total phosphorus load in general all shows an increasing trend during 2046 to 2064.Under B1 and A2 scenario the total phosphorus load change trend is consistent,all showing bigger in July and August and smaller from December to February;under A1 B scenario the total phosphorus load is bigger in May,July,August and September and lower from November to February.Under the three scenarios the total phosphorus load shows high in east and low in west,which is consistent with the spatial distribution pattern of sediment yield in the basin.