Study On Simulation Of Absorbed Nitrogen And Phosphorus Quantity Of Slope Farmland With Purple In Three Gorges Reservoir Area

Agricultural non-point source pollution load accounting for77.85%of thepollution load in Three Gorges Reservoir Area. The main soil type of the reservoir areais purple soil, purple soil is a valuable agricultural soil resources that accounting for38.55%of the total area of Three Gorges Reservoir Area, most of that is slope farmland.Originating from purple shale soil, the structure of purple soil is characterized by largeporosity, shallow soil, high infiltration capacity, and weak underlying shale permeability.Coupled with intense human activities, as well as abundant and concentrated rainfall,frequent heavy rainfall and other reasons, which result in land soil erosion is veryserious of slope farmland with purple soil in Three Gorges Reservoir Area. The nitrogenand phosphorus element carried by soil erosion were the substantial clause whichcaused entrophication. Under the effect of the corrosive rainfall, the outflow quantity ofthe absorbed nitrogen and phosphorus which in the surface layer soil was increased,which caused the soil impoverishment and the entrophication tendency of the surfacewater was obvious day by day. Basin loses sand and the massive absorbed nitrogen andphosphorus were brought into the reservoir water body to pose the threaten seriously.Therefore, how to effective control the soil erosion of slope farmland with purple soil inThree Gorges Reservoir Area is very important for the protection of farmland and waterquality.A spatial database was established inculding weather, topography, land use, soiltype, vegetation cover etc. based on GIS technology. Using the Revised Universal SoilLoss Equation (RUSLE), soil erosion was calculated and analysed in Three GorgesReservoir Area; By considering the actual terrain factors of slope farmland with purplesoil in Three Gorges Reservoir Area. In this paper a new estimation method was putforward which can reflect the actual situation of sediment output in the reservoir and aSpatial and temporal distribution model was constructed about adsorbed non-pointsource pollution load of slope farmland with purple soil in Three Gorges Reservoir Area.The established load model has been verified by observation data. Based on the efficacythat the slope farmland transformation technologies of reducing soil erosion used to thewhole slope farmland with purple soil of Three Gorges Reservoir Area was predictedand analyzed, which was developmented by the institute of Mountain Hazards andEnvironment,CAS. The slope farmland transformation technologies in this paperinclude two kinds, that is, large cross slope combined with small along slope and ridge combined with hedgerow. In order to provide a reference for the soil erosion control andregulation of slope farmland with purple soil in Three Gorges Reservoir Area. Theresults show that:(1)Through the spatial analysis and calculation, for climatic and land useconditions in2010, the soil erosion modulus of slope farmland with purple fortraditional farming technology was4819.00t/(km2a), and that if the technology oflarge cross slope combined with small along slope was used, the soil erosion moduluswould be2837.63t/(km2a); if the technology of ridge combined with hedgerow wasused, the soil erosion modulus would be1737.11t/(km2a).Because the soil erosion was serious of slope farmland with purple soil, therefore,the slope farmland transformation technologies can reduce effectively the soil loss ofslope cropland with purple soil for Three Gorges Reservoir Area, that was beneficial tothe sustainable use of farmland and water environment security.(2)If traditional farming technology was used for slope farmland with purple, forclimatic and land use conditions in2010, the loads of adsorbed nitrogen and phosphoruspollution were35731.33t and18732.93t. The proportion of adsorbed nitrogen andphosphorus load accounting for the total load are about65.61%and34.39%. And that ifthe technology of large cross slope combined with small along slope was used, the loadsof adsorbed nitrogen and phosphorus pollution were21081.48t and11052.43t, the loadsof adsorbed nitrogen and phosphorus pollution reduced by41.12%. If the technology ofridge combined with hedgerow was used, the loads of adsorbed nitrogen andphosphorus pollution were12863.28t and6743.85t, the loads of adsorbed nitrogen andphosphorus pollution reduced by63.59%comparing with traditional farming technology,and comparing with the technology of large cross slope combined with small alongslope, that reduced by38.98%.(3)According to the spatial distribution, the loads of adsorbed nitrogen andphosphorus pollution droped from east to west. The pollutant loading of Kaixian,Yunyang, Fengjie and Digui were serious, and the pollutant loading of Wanzhou,Zhongxian, Shizhu and Banan were not so serious, in the west of Three GorgesReservoir Area, The pollutant loading is light.