中文摘要：

三峡水库蓄水改变了下泄的水沙条件,引起坝下游水沙过程及泥沙输移特性发生变化,影响下游河床沉积物的渗透系数。基于黄河花园口实测沉积物渗透系数与颗粒粒度参数,拟合了渗透系数K关于平均粒径d50及分选系数σ的经验公式,并用该公式分析了三峡水库蓄水前后下游河床沉积物K的变化。结果表明：（1）三峡水库蓄水前、后三峡大坝下游渗透系数K整体上均呈向下游减小趋势,且越接近河口,变化幅度越小;（2）城陵矶以上河段,水库蓄水运用之后,渗透系数K值较蓄水前明显增大;（3）大通至徐六径断面间河段,水库蓄水后较蓄水前渗透系数K值变化幅度存在减小趋势。

英文摘要：

The impoundment of the Three Gorges Reservoir has changed the conditions of water and sediment discharge,correspondingly changed the characteristics of water and sediment transportation in the downstream channel and affected the hydraulic conductivity of the downstream riverbed sediments.Based on the actual measurement of hydraulic conductivity and particle size parameters in Huayuankou of the Yellow River,the empirical formula of hydraulic conductivity on the average grain size and sorting coefficient is fitted.The formula is treated as a tool to analyze the variation of hydraulic conductivity in the downstream riverbed before and after the impoundment of the Three Gorges reservoir.The results show that（1） the hydraulic conductivity values in the downstream decrease on the whole before and after the impoundment,and the variation in magnitude becomes smaller as approching the estuary.（2） After the impoundment of reservoir,the hydraulic conductivity values in the upper reaches before Chenglingji increase significantly compared with those before the impoundment.（3） After the impoundment of reservoir,the variation of hydraulic conductivity reduce significantly compared with that before water storage in the downstream channel between Datong and Xuliujing.