GIS-based Non-point Source Pollution Critical Area Analysis in the Three Gorges Reservoir

Abstract

After erection of the Three Gorges Dam, water environment in reservoir area will be paid more and more attention. With strengthening control of point source pollution, non-point source pollution has become the key factor to degrade water quality in the reservoir area. By using GIS, without computing the amount of sediment or nutrient load, this paper use a modified universal soil loss equation (USLE) model to reveal non-point source pollution critical area which is an important indicator to control the water quality effectively. The results show that risk and sub-risk areas in study area are 3.71% and low risk areas 6.76%. Risk area and sub-risk area are mostly in the vicinity of the rivers and areas with steep or long slopes, which are mainly located in the hilly and rocky regions in the northern part of the Three Gorges Reservoir area, are critical for non-point source pollution. Yunyang, Fengjie and Wanzhou counties are very high in the number of critical area, the sum critical areas in these three counties are more than 100km 2 . And Fengjie and Wanzhou counties also contain large sub-risk areas. The analysis shows that more attention should be paid to Yunyang, Fengjie and Wanzhou counties, providing important reference values for the effective control of non-point source pollution of the Three-Gorge Reservoir area. (GIS) is a tool for the management, query, visualization and analysis of spatially referenced information. Benefits of GIS are the ease of data update, data management, and data presentation in forms most suited to user requirements. Significant advancements in the application of GIS for solving non-point source pollution problems have taken place over the past several decades (Zhang et al., 2003). And also the universal soil loss equation (USLE) formulated by Wischmeire and Smith in 1978 is a possible model to handle this kind of problem. The USLE model was developed to estimate the annual amount of sediments eroded form the surface of the surface of an analysis area. Because of the similarities of erosion and the no-point source problems, the USLE also be used to pinpoint critical non-point pollution areas. In this work, a modified version of USLE is used to analyze non-point source pollution critical area in the Three Gorges Reservoir area of Chongqing with support of GIS technique. It is expected that the study will show where non-point source pollution are easily occurred and provide some support to land use planning and management, and at last arrive to the target of sustainable development.