Sediment transport law during flood event flowing into the Three Gorges Reservoir

Sediment load during flood events flowing into the Three Gorges Reservoir is crucial for reservoir sedimentation management, flood control, and power generation. Based on measured data from major hydrological stations for the period 1960-2024, this paper systematically investigates the characteristics of sediment load flowing into the Three Gorges Reservoir using methods such as mathematical statistics and causal analysis. The results indicate that the flood volume of individual events at each station accounts for 15.1% – 64.1% of the annual runoff, while the sediment load of these events accounts for 32.8% – 98.9% of the annual sediment load. At a significance level of 0.05, the flood event volume at each station shows a statistically insignificant decreasing trend, whereas the sediment load during these flood events shows a significant decreasing trend. As the flow rate increases, the reduction in sediment concentration during flood events gradually lessens across different periods. Under the influence of natural and human activities, the proportion of clockwise hysteresis loops between sediment concentration and flow rate exhibits a decreasing trend, whereas the proportion of counterclockwise loops exhibits an increasing trend. The sediment load during flood events at the Zhutuo and Cuntan Stations is most significantly affected by human activities, followed by the Beibei Station, with the Wulong Station being the least affected. The research findings of this paper can provide a valuable reference for understanding of the flow and sediment characteristics of the Three Gorges Reservoir and for informing reservoir sediment reduction operations.