Rainfall Erosivity Of Three Gorges Reservoir Area

Three Gorges Reservoir Area is a special geographical position in China. Studying the rainfall erosivity in it is of great importance in quantitative prediction of Soil Erosion, soil and water conservation planning, and of great guiding significance in executing comprehensive soil erosion control programs.Based on the precipitation data of 43 weather stations in and around Three Reservoir Area during the period of 1976-2005, the temporal-spatial distribution characteristics of precipitation in this area were analyzed by using Mann-Kendall test and radial basis function methods. The results showed that:1. The annual precipitation had a decreasing tendency in the study area during the last 36 years, and the decrease rate of average annual was 1.32mm, the precipitation decreased in autumn was the main reason of annual precipitation reduction. Spatially average precipitation showed an increase trend from west to east in the study area, There have two decline centers were Wanzhou, Kaixian and Wuxi, respectively, and an increase center near Changshou.2. Daily precipitation model created by ZhangWenBo is more suitable for calculating the rainfall erosivity in Three Gorges Reservoir Area. According to ZhangWenBo's model, monthly rainfall erosivity from 1971-2006 had been calculated, the power function format of erosion R values of annual rainfall agents based on monthly/annual rainfall data was obtained by the fitting formula.3. The results of statistical analysis showed that the coefficient of variation of monthly, quarterly and annual average rainfall erosivity in reservoir area was varied between 0.168～0.523, which was in the middle range of variation; data can be used directly in variogram analysis system except for January and Februaty data which showed skew effect and should be converted before analyzed by Kriging interpolation analysis; selected the optimal model for monthly, quarterly, annual average rainfall erosivity to carry out variogram analysis in GS+; the analysis results showed that Co-Kriging which considered the elevation effects performed best in the Three Gorges reservoir area.4. There was a decreasing trend of rainfall erosivity in the Three Gorges reservoir area, the average annual reduction was 15.82 MJ·mm·hm-2·h-1·a-1, the decreasing of autumn rainfall erosivity is the main reason for the decline of the rainfall erosivity in the reservoir area. There were significant difference in space distribution of rainfall erosivity changes in reservoir area, rainfall erosivity was increased from west to east, there were two increasing centre, Yiling which was in Hubei province and Beibei which was in Chongqing municipality; two decreasing centre, Fengjie and Wulong which were both in Chongqing municipality. Overall, east area showed the most significant trend in the last 36 years, the central region declined slightly as a whole and relatively stable, while the western part (except for Jiangjin) showed obvious upward trend in summer and winter. Therefore, water and soil conservation should be strengthen in winter, and enhance the soil erosion control for east and northwest regions where rainfall erosivity had increased.