Sediment delivery regularity and its influencing factors during flood events in the Three Gorges Reservoir
摘要
Reservoir sedimentation leads to a loss of storage capacity, thereby affecting the ability of a reservoir to fulfil its designated purpose. Accordingly, it is important to investigate the regularity of sediment delivery to constrain reservoir sedimentation. On the basis of data recorded at Zhutuo, Beibei, Wulong, Cuntan, and other hydrological stations between 2003 and 2021, individual flood events in the Three Gorges Reservoir (TGR) were identified. The regularity of sediment delivery during each flood event was then analyzed. The impacts of factors such as the water level in front of the dam, the rate of sediment transport into and out of the reservoir, and flood detention time on sediment delivery during flood events were investigated. The results indicate that it is more reasonable to classify the flood events in the TGR by considering the asynchronous propagation of flood and sediment peaks on the basis of a unified quantitative standard. Sediment delivery in the TGR occurred mainly during flood events, accounting for 67.0% of the annual sediment delivery volume. The sediment delivery ratio (SDR) during the flood events was inversely proportional to the water level in front of the dam and proportional to the sediment transport rate into and out of the reservoir. However, the correlations were weaker than that between the SDR and flood detention time, whereby the SDR was inversely proportional to the flood detention time. The correlations between the SDR and other factors were strongest during flood events when the average inflow was greater than 30 000 m3/s or the average water level in front of the dam was less than 150 m. This study provides an important reference for optimizing the operation of the TGR and reducing sediment deposition.