| Soil erosion,as a non-point pollution,may increase the risk of eutrophication for the nutrients in the soil get into water,which has aroused fears among society.In recent years,with the rapid development of Remote Sensing(RS),Geographic Information System(GIS),Global Positioning System(GPS)technology and intensive study of the mechanism of soil erosion,the combination of the 3S technology and soil erosion assessment models makes it easier for accurately evaluating soil erosion and that kind of method is getting more and more attention.The plateau lakes,represented by the Dian lake and Xingyun lake in Yunnan are one of the most disturbed area that affected by human disturbance,water quality decline,and water eutrophication problem.Xingyun lake is an important water resource that support that development of agriculture and industry in Jiangchuan country,and plays a key role in the ecological environment and economic development of the Basin.Degradation of the lake water have a bad influence in the ecological integrity and sustainable economic development of the region.Based on the basic spatial and attribute data of land use,vegetation,soil,topography,meteorology and hydrology,the soil erosion status and its distribution was simulated by GIS technology and USLE model;runoff and non-point source nitrogen and phosphorus load was simulated by GIS technology and SWAT model.The main conclusions are as follows:1.The soil erosion and its spatial distribution in the Xingyun Lake Basin were analyzed.The total area of soil erosion is 221.09km2 i 1014 and the average erosion modulus is 34.07t/km2·a.Soil erosion in 2014 was mainly composed by moderate erosion and below,accounting for 96.67%of the total erosion area.Intensive erosion is less,mainly distributed in the north of the basin.2.The multi-year runoff and non-point source nitrogen and phosphorus load in the Xingyun Lake basin were obtained.The coefficient of determination(R2)of the linear regression equation for the simulated monthly runoff and the measured monthly flow rate is 0.87 and 0.88 respectively on calibration period(2012-2013)and validation period(2014);the R2 for the rate of non-point nitrogen and phosphorus load were 0.89,0.83.The simulation results show SWAT model is suitable for the simulation of runoff and non-point source nitrogen and phosphorus in the Xingyun Lake basin.3.The relationship between soil erosion,non-point source pollution and main soil erosion factors in the Xingyun Lake watershed is revealed by using GIS technology.(1)Soil erosion mainly occurred between 15° and 35°,intensive erosion mainly occurred above 35°;(2)There is a quite diversity in soil erosion status in different land use types.The forest erosion area is the largest,but mostly moderate and below erosion.(3)Non-point source pollution is mainly concentrated in the fourth sub-basin,mainly due to the largest runoff in the sub-basin,and the largest agricultural land area. |
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