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流域大型水库蓄水后，坝下游河道调整过程中的洪、枯水位变化，对下游水安全、水生态和水资源利用影响甚大.利用1955-2012年长江中游各水文站水位、流量等资料，采用改进的时间序列分析方法，对三峡水库运行前后长江中游洪、枯水位变化特征进行了研究，结果表明：三峡水库蓄水前长江中游洪、枯水位变化的周期长度分别为9~14、11~15 a，在假设三峡水库运行后水位无趋势性变化的前提下，估算得到的水位变化周期长度基本在20 a以上，蓄水前的自然周期性已被打破，枯水位发生趋势性下降且无复归迹象，而洪水位波动周期虽有所延长，但上升幅度未超过历史波动变幅，仅可确定洪水位没有明显的下降趋势.三峡水库蓄水后坝下游长距离冲刷，枯水河槽冲刷量占平滩河槽的比例逐年增加，累计至2013年已达91.5%，是枯水位下降的主控因素.河槽冲刷导致的床沙粗化增加了河道床面阻力，高程在平滩水位附近的滩体上覆盖的大量植被增加了水流流动阻力，同时大量航道整治、护岸、码头等工程主体部分布设在枯水位以上，综合因素作用使得洪水河槽阻力增加.三峡水库蓄水后，虽然枯水期流量补偿作用显著削弱了枯水位下降的效应，但枯水位下降事实已经形成，不利于航道水深的提高及通江湖泊枯水期的水量存蓄，洪水位未明显下降，同级流量下的江湖槽蓄量不会明显调整.;The flood and low stage adjustments in downstream reach of reservoir projects have an important effect on water security,water ecology and water resource utilization.The variation features of the water stages are studied in the middle Yangtze River after impoundment of the TGR,based on the hydrological data via one improved method of the time series analysis.The results and con-clusions are as follows:The low water stage exhibited a decreasing trend due to its periodic time increased from 9-14 years to more than 20 years,while the flood stage had no decreasing trend because its change amplitude was less than the max value in history.The main reason for low stage decline is that the erosion amounts in low flow channel increased year by year,when its proportion accounted for the proportion of bank-full channel even reached at 91.5% in 2013.The river resistance has led to flood stage rising which increased by sand coarsening,vegetation coverage in beach above bank-full stage,and other projects such as navigation reg-ulation,revetment,and wharf etc.Change in the water stages is harmful to the improvement of channel depth and the water storage in the reservoir,although the flow discharge compensation of reservoir improves the low flow stage.The water-storage capacities of lakes have no change because the flood stage is not significantly decreased.
Han et al. (Sun,) studied this question.