Assessing the effects of land use changes on soil erosion in Three Gorges Reservoir Region of China

The Three Gorges Project (TGP) is a vital project in the development and harnessing of the Yangtze River in China. The Three Gorges Reservoir region, while with serious soil erosion for a long time, is one of the typical regions whose ecological environment is very fragile. The objective of this study is to map the inter-annual spatial changing pattern of mean soil erosion and assess the effects of land use changes on soil erosion for this area. This paper presents a comprehensive methodology that integrates an erosion model, the Revised Universal Soil Loss Equation (RUSLE) with a geographic information system (GIS) and remote sensing (RS) technology for estimating soil erosion in the Three Gorges Reservoir area. Firstly, the basic data of soil, precipitation, vegetation and crop management, and the DEM, land use map and Landsat TM images of Three Gorges Reservoir region were collected. With the aid of GIS and RS technology, the value for R, K, LS, C and P factors used by RUSLE in the estimation of soil erosion were computed respectively using suitable methods. Then based on the RUSLE the mean soil erosion amount and the soil erosion modulus in 1977 and 2005 of this region were obtained. Finally, keeping the R, K and LS factors invariant, we analyzed the effects of land use changes between 1977 and 2005 on soil erosion for the Three Gorges Reservoir region. The results show that the mean soil erosion amount and the soil erosion modulus in Three Gorges Reservoir region were 18476.27times10⁴ t/a and 3316.53 t/(km².a), respectively. The annual soil conservation amount was 48427633times10⁴ t/a. The average soil conservation capacity of Three Gorges Project region is 156.27. By comparison of the soil erosion between 1977 and 2005, we can see that the total soil erosion amount decreased by 449.07times10⁴ t and the mean soil erosion modulus increased by 13.17 t/(km².a) from 1977 to 2005 because of the land use change. - - The integrated approach in this study allows for relatively easy, fast, and cost-effective estimation of spatially distributed soil erosion and analyses of the land use changespsila effects on soil erosion. It thus provides a useful and efficient tool for predicting long-term soil erosion potential and assessing erosion impacts of conservation support practices.