三峡水库蓄水以来水库淤积和坝下冲刷研究

为了分析三峡工程对库区及坝下长江中游河势的影响，基于实测资料，较为系统地研究了三峡水库蓄水运用以来水库泥沙淤积和坝下游河床冲刷特性。研究表明，1991年以来长江干流各站径流量变化不大，输沙量明显减小；三峡水库蓄水运用后的2003～2011年入库沙量继续大幅减少，仅为原设计值的40%，水库年均淤积泥沙1.40亿t，也仅为论证阶段的40%左右，且绝大部分淤积在常年回水区和死库容内；受上游来沙减小和三峡水库蓄水拦沙影响，坝下游输沙量大幅减小，悬移质泥沙颗粒也明显变粗，长江中游原有的冲淤相对平衡状态被打破，河床发生沿程冲刷，2002年10月至2010年10月，宜昌至湖口河段总冲刷量为9.79亿m3，河床冲淤形态转变为“滩、槽均冲”，主要冲刷发生在宜昌至城陵矶河段。

Research on reservoir sedimentation and downstream channel erosion of dam after impoundment of Three Gorges Reservoir

In order to analyze the influence of TGP on the reservoir sedimentation and downstream channel erosion since impoundment of Three Gorges Reservoir,based on measured data,this paper systematically presents the research on the reservoir sedimentation and channel erosion of middle Yangtze River.The research results show that the runoff at the control stations of the main stream has little change,but the sediment discharge reduces evidently since 1991;from 2003 to 2011,the reducing trend of the inflowing sediment is still enduring obviously,but just accounting for 40% of the design value,with the annual reservoir sedimentation of 1.40×108 t,and the most deposited in perennial backwater area and dead storage of reservoir.Influencing by the decrease of sediment from upstream and the reservoir sediment retaining function,the sediment discharge in downstream of the dam reduces to a large extent,the suspended load is coarsened,thus the equilibrium of mid-lower reaches of Yangtze River is broken obviously,and the channel erosion appears.From Oct.2002 to Oct.2010,the total erosion is 9.79×108 m3;the erosion occurred in both grooves and shoals,and channel erosion mainly occurs in the reach from Yichang to Chenglingji.