中文摘要：

根据黄河上游位于弯曲—顺直过渡段的头道拐断面的多年实测水文、泥沙数据和断面资料，分析了断面对上游一系列水利工程在时间尺度上的调整响应过程。结果发现，头道拐断面的形态变化强烈受到上游水库运行的影响，在一系列水库投入运行后，河床粗化现象一直持续到三湖河口断面以下。头道拐断面悬移质泥沙中值粒径在水库运行后表现为先增大，然后减小，最后再增大的三阶段性特征，并且自1986年龙羊峡与青铜峡、刘家峡等水库联合运用以后，该三阶段性特征的变化幅度明显较只有青铜峡、刘家峡水库单独运行时段（1969-1986年）小。另外，自1987年以来，头道拐断面河道的横向摆动速率大幅减小，断面形态及位置趋于稳定，有利于当地百姓正常的生活和生产。

英文摘要：

The application of dams built upstream will change the input conditions, including water and sediment of downstream channel system, and destroy former dynamic equilibrium, so necessary adjustments are demanded for the downstream channel to adapt to the new water and sediment supply, which will lead to the downstream channel to restore its former equilibrium or reach a new equilibrium. Using about 50 years of hydrological, sediment and cross-sectional data, spatial response process of Toudaoguai cross-section to the application of dams built upstream was analyzed. The results showed that the Toudaoguai cross-section change was influenced strongly by the application of upstream dams and armoring happened and extended to the channel down the Sanhuhekou cross-section. Median diameter of sediment particle experienced a three-stage changing trend which was characterized by an increase at first, then decrease and increase again finally, since the joint application of Longyangxia, Qingtongxia and Liujiaxia reservoirs in 1986, the three-stage changing trend has become less obvious than the time period between 1969 and 1986 when only Qingtongxia and Liujiaxia reservoirs were put into operation.