Simulation Of Soil Erosion In The Three Gorges Reservoir Area Under Different Land Use

Three Gorges Dam as one of the world's major water conservancy projects,its construction formed the Three Gorges reservoir area.Witch located at the end of the upper end of the Yangtze River,not only related to the safety of the Three Gorges Project,but also related to the Yangtze River Basin ecological security.The construction of the Three Gorges Dam and the subsequent relocation of cities and towns,resettlement will certainly cause disturbance to the surface morphology of the area,and then affect the regional land use and climate environment and thus affect the soil erosion process.A series of environmental problems caused by soil erosion are one of the major environmental problems in the world and the most serious environmental problems facing the region.Soil erosion leads to a large number of sediment directly into the reservoir,siltation will greatly reduce the effective reservoir capacity,shorten the life of the Three Gorges power station,at the same time trigger and aggravate the Yangtze River flood.Based on 3S,the Universal Soil Loss Equation(USLE)has been used to calculate the soil erosion of the five years,1990,1995,2000,2005 and 2010,in the Three Gorges Reservoir Region.In addition,quantitative analysis has been used to reach the temporal and spatial variation of soil erosion intensity from 1990 to 2010 and the distribution of soil erosion under the different background of land use.And all of above will contribute a lot to the sustainable development of the Three Gorges Reservoir Region.Based on characteristics of Erosion Rainfall in 1990,the rainfall erosivity of 75 stations was simulated and verified by BP neural network.After that,rainfall erosivity at75 stations in 2030 were predicted.The rainfall erosivity of the 28 stations in the Three Gorges Reservoir area and the surrounding area were analyzed by Kriging interpolation.The soil erosion intensity of the Three Gorges Reservoir Area in 2030 was simulated by using the generalized loss equation(RUSLE),using the land use data of natural growth scenario or the ecological protection scenario in 2030 and data of BP simulation results.The results were showed as follows:(1)During the period of 1990-2010,the average soil erosion modulus and soil erosion in the Three Gorges reservoir area generally showed a decreasing trend,and the Three Gorges Reservoir Region belongs to middle erode area with the amount comes to18356.45 million tons.The spatial distribution of soil erosion has the characteristics of imbalance,which mainly shows the trend of decreasing from east to west,and the micro and light erosion are the most widely distributed grades of soil erosion.(2)During the period of 1990-2010,paddy fields,grassland area has declined,waters,construction land showing a growing trend.The land use change in the construction area of the reservoir area is the fastest growing rate,followed by waters.The interchange of paddy and dry land,the transfer and transfer of paddy field and dry land,the interchange of forest and grassland,the flooding of forest land and grassland is the main way of land use conversion in the 20 years in 1990-2010.(3)The soil erosion modulus of six different land use types in the same year turn out to be: dry farmland> grassland> forestland> unused land> paddy field>construction land;The area of each land use type of slight erosion gradually increased;with returning farmland into forest and grass and large transferring of rural labors,the soil erosion in the Three Gorges Reservoir Region shows an improving trend as a whole,but regional governance work still needs to be strengthened.(4)The relative error of simulated rainfall erosivity in 2010 was 15%,the relative error of the sample data was 14.67%,the relative error of prediction was 19.65%,and the NE factor was 0.85,indicating that BP had a good ability to simulate rainfall erosivity;the Kappa coefficient,verified from the result of soil erosion intensity type simulation in 2010 was 0.75.(5)In the case of land use unchanged,the areas of light-erosion and moderate erosion increased with the areas of erosion above the intensity showed an decreasing tendency,and 58% of the soil erosion intensity type changed only occurred between the adjacent erosion intensity;in the case of rainfall erosivity unchanged,the soil erosion under the different land use scenarios in the future showed a downward trend,and the soil erosion under the ecological protection situation was more obvious than that under the natural environment;In the case of rainfall erosivity and land use change,the soil erosion under the ecological environment and the natural environment showed a trend of recovery.