Investigation of Sedimentation in the Three Gorges Reservoir, China

The Three Gorges Reservoir (TGR) is the largest built hydropower reservoir in the world, having comprehensive functions of flood control, power generation, navigation and irrigation. The construction of the TGR has greatly changed the upstream flow field and generated a complex sediment transport. Sedimentation in the TGR is a major factor affecting reservoir function and reservoir life and is also a controversial issue. In this study, long-term series field measured hydrological and terrain data before and after the TGR`s impoundment are used to investigate the trend of runoff and sediment load transport into the TGR. The effect of sedimentation on the TGR is discussed. The result shows that the total amount of sediment load transported into the TGR has a significant reducing trend after the impoundment of the TGR. Analysis of the field data shows that the average sediment delivery ratio of the TGR is 24% during 2003-2016 and the annual loss in storage capacity is about 0.3%. Sediment mainly deposits in river reaches with wide cross sections, especially in the permanent backwater area, where the flow velocity is relatively small. It is expected that this study will help optimizing the TGR operations and improving its comprehensive function.