Benefits of the sediment peak regulation during the flood season in the Three Gorges Reservoir

<p indent="0mm">In response to the new situations posed by water-sediment inflows and the evolving demands of various societal sectors, the Three Gorges Reservoir (TGR) has implemented five instances of sediment peak regulation (SPR) since 2012. A systematic review is necessary to elucidate the underlying scientific mechanisms and to optimize the benefits of SPR. This study analyzes the impacts of SPR on sediment transport, deposition distribution, and sediment flushing of the TGR, employing data analysis and mathematical modeling. The findings reveal that (1) SPR actively contributes to reducing sedimentation by reshaping the outflow process and concentrating sediment flushing when the sediment peak reaches the dam front. The driving effect of the flood inflow and the water level on hydrodynamics contributes to enhancing sediment delivery ratios. (2) SPR advances the sediment peak arrival at the dam by an average of <sc>14.4 h,</sc> resulting in a corresponding average increase of 3.7% in sediment peak concentration and 2.2% in sediment delivery ratio. (3) SPR redistributes sediment deposition, with a 7:3 ratio between the permanent and fluctuating backwater areas and a 4:1 ratio between dead and flood control storage capacities. The primary sediment reduction area is located in the Fuling-to-Yunyang River section; the vertical deposition distribution shifts from flood control to dead storage capacity in the reservoir tail area and near the dam front. (4) Initiating the phase of “sediment transport in the reservoir” earlier enhances the sediment peak concentration at the dam, promotes sedimentation reduction in the fluctuating backwater area, and improves the deposition distribution of the TGR. Correspondingly, increasing the outflow to control the water level can further expand the sedimentation reduction range in the tail area and promote sediment flushing.