Spatio-temporal Dynamic Regularity Of Soil Erosion In Daning River Watershed In Three Gorges Reservoir Area

In this study,the temporal and spatial variation of soil and water loss in the Daning River Basin of the Three Gorges Reservoir area was studied by SWAT model.This paper regards.runoff and sediment change process as the starting point to explore the comprehensive effection of land use,soil and slope on soil and water loss.In order to gain a better understanding of the soil erosion in the Three Gorges reservoir area,this research analyzed the temporal and spatial characteristics of soil and water loss and its internal mechanism.The conclusion will provide theoretical basis for the prevention and control of soil and water loss in this area,and even provide support for soil quality improvement and land use planning in this area.The main results of this paper are as follows:(1)The author systematically studied the determination method of soil property parameters,and constructed a high-precision soil database combined with high-precision soil spatial data.After that,the Daning River SWAT model was constructed based on DEM,land use and meteorological data.In the course of the experiment,The author use the LH-OAT method,SWAT-CUP software and SUFI-2 algorithm for parameter sensitivity analysis,parameter rate setting,model validation and uncertainty analysis.The results show that,the deterministic coefficient of the runoff and sediment rate is greater than 0.71 and the Nash efficiency coefficient is greater than 0.86 and the relative error is less than 3.2%.The simulation results are accurate.(2)The dynamic regularity of soil and water loss in Daning River watershed is studied by coupling SWAT model sub-basin output results and township unit.And the results show that,?annual runoff depth,sediment yield,soil erosion intensity of all townships are increase first,and then decrease since 2006.?The maximum depth of runoff occurred in September and July,and The maximum sediment yield was found in June,followed by April.?The average annual runoff depth,sediment yield and soil erosion intensity are higher in the townships in the upstream area of the watershed,and the spatial distribution characteristic is northwest higher than southeast.(3)The effect of land use,soil and gradient on soil erosion is systematically studied by using the output of Hydrological Response Unit(HRU).And the results show that,erosion degree of land use types in Daning River watershed is cultivated land>forest land>grassland,and among them,cultivated land is intensity erosion,forest land and grassland are mild erosion.Erosion degree of soil types is purple soil>yellow soil>yellow brown soil>limestone soil,and among them,purple soil and yellow soil are moderate erosion while yellow brown soil and limestone soil are mild erosion.Erosion degree of slope types is soil erosion intensity increases with the slope increases to a certain extent.(4)The comprehensive influence of three kinds of factors on soil and water loss was studied by HRUs.And the results show that,the largest combination of annual soil erosion modulus are forest land-purple soil->30°,forest land-yellow brown soil->30° forest land-yellow brown soil-15°?30°,cultivated land-yellow brown soil->30° and cultivated land-Purple soil->30°.Among them,the largest is 12653.55 t/(km~2 · a)and the smallest is 8595.37t/(km~2·a).