梯级水库对长江水沙过程影响初探

长江中上游干流及主要支流正在进行大规模水电开发，按目前的规划和建设步伐，在未来20~30年，这些河段将形成一系列梯级水库。根据近20年来水文观测和资料统计，初步分析了长江水沙变化情况和发生变化的原因；通过一些已建大型水库的观测资料，分析了水库对泥沙输移规律的影响方式和程度；最后，提出减小梯级水库对长江生态环境影响的对策和建议。分析表明：长江的水沙过程已经发生变化，绝大多数河段输沙量明显减少；梯级水库的建设是输沙量减少的主要因素之一；梯级水库建设不仅使输沙量和径流量减少，而且显著改变了天然河流的水沙过程，给长江中下游及河口地区生态环境带来一定影响。为了减小梯级水库对河流自然属性的影响，必须转变长江治理的思路，由江河治理向科学管理转变，利用洪水冲沙和水库群的优化调度，尽量维持河流的自然属性。

PRELIMINARY STUDY ON THE CHANGE OF WATER FLOW AND SEDIMENT PROCESS IN THE CHANGJIANG RIVER

A large scale of waterpower projects have been and will have been constructed in the main upper and middle reaches of Yangtze River and its tributaries. According to the completed plan and construction step cascading reservoirs along these rivers will appear in future 20-30 years. Based on hydrological observation and data collected over last 20 years the change of water flow and sediment in Yangtze River and their occurrence reason were analyzed. With some observations to a few completed reservoirs, the impact manner and degree of sediment transportation rule were discussed. Finally some measures and proposals to decrease environmental effect as cascading reservoirs were suggested. It appeared that the flow and sediment process have changed, and sediment-transporting quantity have obviously reduced in most river channels. Cascading reservoirs are one of the most important factors inducing the decreaes of sediment-transportation. Cascading reservoirs not only decrease sediment transportation and runoff, but also significantly change natural water flow and sediment process. All of these may influence the environment of middle , down streams and estuary of the river. In order to reduce the effect on river features after the completion of cascading reservoirs, it is necessary to change the way in which the river is exploited for hydropower and is manipulated for flood control. Using flood to scour sediment and optimizing cascading reservoirs regulation will maintain nature river at a possibly natural condition.