Mapping soil erosion risk in Danjiangkou Reservoir Area using RUSLE, RS and GIS: A case study of Danjiangkou City

Danjiangkou Reservoir is a water resource of Middle Route Project under the South-to-North Water Transfer Program in China. In order to guarantee the quality of the transferred water, the central and local governments have worked very hard to curb point source pollutant emission since the late 1990s. However, non-point source (NPS) pollution due to agricultural activities and soil erosion continues to be a serious problem. Evaluation of current situation of erosion is very important for improvement of endangered areas, and determining the type of conservation measures to be applied. This article discusses research in which the authors applied to the Revised Universal Soil Loss Equation (RUSLE), Remote Sensing (RS), and Geographical Information System (GIS) to the mapping of soil erosion risk in Danjiangkou City. All factors used in the RUSLE were calculated for the study area using local data. Soil map and soil survey data were used to develop the soil erodibility factor (K), and a digital elevation model image was used to generate the topographic factor (LS). The cover-management factor (C) was developed based on vegetation, shade, and soil fraction images derived from spectral mixture analysis of an Indian Remote Sensing satellite IRS_P6. Assuming the same climatic conditions and no support practice in the study area, the rainfall-runoff erosivity (R) and the support practice (P) factors were not used. A soil erosion risk map with five classes (very low, low, medium, medium-high, and high) was produced based on the simplified RUSLE within the GIS environment, and was linked to land use map to explore relationships between soil erosion and land use distribution. The results indicate that most forests were in very low and low erosion risk areas,while sparse forest and cropland were usually associated with medium to high-risk areas. This research implies that RS and GIS provide promising tools for evaluating and mapping soil erosion risk in Danjiangkou Reservoir Area.