水电开发对河流水沙变化的综合影响评价新方法(英文)

The environmental impact assessment (EIA) of cascade dams building in international rivers has been widely discussed in China and ASEAN countries since the 1990s. In Southwest China, all the great mountainous rivers have been the major state base for large-scale hydropower development. Among these rivers, the environmental change and response of the watercourse under the cascade dams building in the upper Mekong (called Lancang River in China) has been the focus in recent 20 years. In this paper, the Lancang River, which has over 25 years of large-scale hydropower development, was chosen as a case study for establishing the affected evaluation indicators system and its regression model of runoff and sediment, determining the indicators weight by the hierarchy analysis method and factor analysis method, and setting up the quantitative evaluation models of indicators affected level based on the "marginal efficiency" principle. Using these methods and model established, the influence degree of runoff and sediment in the Lancang River from 1986 to 2007 were assessed. The major results are: (1) the impact of sediment transport change by the cascade development is much higher than that of the runoff change; (2) the years' number with different impact levels respectively are 72.7% as the "smallest" level, 18.2% as "smaller", and 9.1% as "general"; (3) the change process of runoff and sediment shows a "U-shaped" pattern, which indicates the balance of sediment change because of the interaction of sediment reduction by Manwan reservoir storage and the increase by the Dachaoshan dam construction.