Abstract: This article is based on the Three Gorges reservoir's operation at water level 175 m and the collected data of topography, hydrology and sediment measurements. We examine the backwater effects in the fluctuating backwater zone of the reservoir after its impoundment. A 2D depth-integrated flow model was adopted in the framework of a SMS surface water simulation code for simulation of the representative Egongyan reach located in the middle of the fluctuating backwater zone, focusing on its hydrodynamic and bedload transport conditions and their responses to the impoundment. The results provide technical support to analysis of riverbed evolution, waterway management, and waterway regulation.