中文摘要：

根据大量实测水文泥沙资料，分析了包括下荆江裁弯、葛洲坝和三峡工程运用后长江中下游河道冲淤与枯水位及泥沙特性变化情况．研究结果表明，近50a来长江中下游枯水位表现为宜昌至监利河段下降明显，城陵矶至螺山上升显著，汉口至大通略有上升．三峡水库运用后，长江中下游含沙量及输沙量下降明显，悬移质中值粒径大幅减小，枯水位降低．枯水位变化与河段河床演变以及河道的冲淤变化密切相关，由此带来的河岸崩塌、引水及航道等问题应引起重视．

英文摘要：

Based on a large number of field data including Jingjiang Truncation, Gezhouba Project and Three Gorges Project＇s impoundment and operation, the variations of river bed and low water level have been analyzed. The research results show that in the past 50 years on the lower reaches of the Yangtze River, the low water level from Yichang to Jianli decreased obviously; but the low water level from Chenglingji to Luoshan raised significantly, and that from Luoshan to Datong increased slightly. After Three Gorges Project＇s impoundment and operation , the sediment concentration and discharge amount decreased obviously; the sediment of middle grain diameter diminished greatly and the lower water level decreased obviously, too. And the low water level is closely related to the river bed evolution and variation. Problems about bank collapse, water diversion and navigation pass caused by the river bed evolution and variation must be focused on.