三峡水库运用后长江中下游造床流量变化及其影响因素

随着三峡水库的运用，其下游的造床流量发生变化，研究坝下游造床流量的变化特性及主要影响因素对河道的冲淤特性及河床演变机理研究有着重要意义。根据1981—2015年的资料，采用平滩水位法、马卡维耶夫法和流量保证率法计算三峡水库蓄水前后宜昌、枝城、沙市、监利、螺山、汉口、九江、大通各站的造床流量。结果表明:①马卡维耶夫法同时考虑了流量过程和输沙能力的影响，计算结果相对合理。②蓄水后各站造床流量减小3 000~6 000 m3/s，符合坝下游主要冲淤变形部位由平滩河槽调整为中枯水河槽的变化特性，反映了结果的合理性。具体来看，时间上，2009年以后造床流量的减小趋势更为明显；空间上，从绝对值来看，以监利站为转折点，从宜昌至大通呈先减小后增大的趋势。③造床流量对来水量和洪峰流量的响应较为敏感，与之呈正相关关系。

Changes in dominant discharge and their influential factors in the middle and lower reaches of Yangtze River after the Three Gorges Dam impoundment

With the impoundment of the Three Gorges Dam (TGD), the dominant discharge in the reaches downstream of the TGD have changed. Studying the changes in dominant discharge and the factors driving these changes is of great importance to illustrating the changes and mechanisms of riverbed evolution in the downstream reaches. Based on data from 1981 to 2015, the Makayev method, frequency analysis and the bankfull level method are used to calculate the pre-and post-dam dominant discharge in Yichang, Zhicheng, Shashi, Jianli, Luoshan, Hankou, Jiujiang and Datong. The results show the following:① Both the flow process and sediment transport capacity are taken into account by the Makayev method, and the results are relatively reasonable. ② The post-dam dominate discharge at each station is reduced by 3 000-6 000 m³/s and is consistent with the adjustment area changing from bankfull channel to medium flow channel, which reflects the rationality of the results. Specifically, through time, the dominate discharge decreases clearly after 2009; spatially, the dominant discharge decreases from Yichang to Jianli and then increases from Jianli to Datong. ③ The dominate discharge is sensitive to the runoff of the incoming flow and peak discharge, and this relation exhibits a positive correlation.