大型水利工程的运行是对天然径流过程的控制，决定着下游干流的水文情势和河道演变，影响沿线各交汇口水沙遭遇过程，从而影响入汇支流的水沙运动及河床变化。国内外研究更多地关注大型水利工程对下游干流的影响，工程调蓄影响下下游非恒定水沙交汇及支流水-沙-河床变形响应方面的研究比较局限，缺乏机理层面的探讨和普适性规律的揭示。本项目拟以大型水利工程下游交汇河道为研究对象，以工程调蓄和河道水-沙-河床冲淤响应为主线，利用现场观测、室内试验、数值模拟和理论分析等多种手段和方法，开展大型水利工程下游河道水沙时空演变机制及河床变化特征、干支流非恒定交汇的水沙通量过程及河床变形响应机制、干支流顶托机理及其驱动机制等方面研究，最终揭示大型水利工程影响下下游交汇河道演变响应及规律。研究成果为进一步开展三峡水利枢纽工程下游长江各大支流治理（如两湖调控与湖控工程的建设）方面的研究提供理论和技术支撑，具有很好的应用前景。

The large-scale water conservancy project can regulate the natural runoff processes, control hydrology and fluvial processes of the downstream rivers, affect processes of flow and sediment encountering at the downstream river confluences, and further influence flow and sediment transport and morphological processes of the tributaries. Previous studies have paid much attention to the influence of the large-scale water conservancy project on the downstream main river, but the knowledge of response of unsteady flow and sediment encountering and fluvial processes of the tributaries to the operation of the water conservancy project is sparse. The discussions on the mechanisms and the reveal of universal theories are desired. This proposal intends to focus on the river confluences downstream a large-scale water conservancy project, and the response of their flow-sediment-morphological processes to the project's operation. Based on field observations, laboratory experiments, numerical simulations and theoretical analysis, we attempt to study the temporal and spatial evolution of flow and sediment and fluvial processes of the main river downstream the large-scale project, the flow and sediment fluxes and response of bed morphology at river confluences with unsteady flow and sediment discharges, and the mechanism of the main river's blocking effect on the tributary and its controlling factors, aiming to reveal the response of fluvial processes of river confluences to the upstream large-scale project. The results can provide theoretical and technological supports for treatment of the tributaries of the Yangtze River downstream the Three Gorges Project, such as the regulation of Poyang Lake and Dongting Lake and the construction of the Poyang Lake Control Project. They shall have a good application prospect.