Abstract: The sediment issue in the Three Gorges Reservoir (TGR) is directly linked to the long-term maintenance of reservoir capacity. In this study we focus on the effects of incoming volumes of and asynchrony between water and sediment as well as operating water levels on sediment peak transport and deposition discharge in the TGR during typical high flood levels using numerical models. The findings indicate that an increase in incoming flood peak hinders the reduction of sediment peak ratio at Fuling Station, leading to more sediment transportation in front of the dam. This results in a greater reduction of sediment peak in front of the dam as the operating water level rises. The variable backwater area is more susceptible to the asynchrony between water and sediment movement compared to the perennial backwater area. As incoming-sediment coefficient rises, the proportion of siltation increases with the rise of low water levels. The sediment delivery ratio is minimally impacted by the asynchrony between water and sediment entering the TGR. As flood and sediment peaks increase, the sediment delivery ratio rises and is more responsive to the attenuation caused by rising operating water levels. These findings provide preliminary insights into the effects of natural water and sediment asynchrony, as well as operating water levels, on sediment movement and deposition in the TGR. This information can serve as a basis for optimizing sediment operations in the TGR.

Key words: sediment deposition, high flood level period, sediment peak attenuation, operational water level, sediment peak transport, reservoir storage capacity, Three Gorges Reservoir (TGR)