Eco-environment evolvement analysis of Ertan reservoir catchment based on remote sensing

Hydropower project may bring with it social-economic profits as well as side effects. The built dam and reservoir often cause some problems to the surrounding areas, among which the ecological and environmental effects caused by hydropower projects are always concerned by the public. In this article, we take the Ertan reservoir catchment as the research area and try to quantitatively analyze the variation of vegetation cover and soil erosion by remote sensing technique, and to comprehensively assess the evolvement and development trend of reservoir catchment. Soil erosion, land use/cover are used as ecological and environmental indicators which reflect the changes before, after and in the period of the construction of Ertan hydropower station. Supported by the multi-source remote sensing data (from satellite Landsat and CBERS) and DEM data, the land use/cover is interpreted through RS images which are classified both by unsupervised and supervised method, and the driving factors of the ecological changes are also analyzed. At the same time, the changes of soil loss are also monitored and analyzed during flood seasons of Ertan reservoir area before and after reservoir impoundment (1995, 2000 and 2005) using the revised universal soil loss equation (RUSLE). The results show that during the recent 13 years the arable land area has decreased obviously, and construction area and water surface have increased slightly. The increase of vegetation cover has some relations with the implementation of local ecological projects, i.e., de-farming to forestry and de-farming to pasture projects. At the same time, changes may also be caused by the climate adjustment in the reservoir area. In the ten years from 1995 to 2005, the high soil loss classes were transforming to lowly level classes continuously. All of these show that the soil loss of Ertan reservoir area is getting better.