Research on the causes of sediment discharge of Sanmenxia Reservoir during flood season

The flushing operation of Sanmenxia Reservoir during the flood season is a key approach to handling the problem of sedimentation and restricting of Tongguan Elevation. Since the application of"Storing Clean Water and Discharging Muddy Flow"(SCWDMF), dynamic balance of scour and deposition in the reservoir has been generally maintained by lowering water level in flood season to flush the cumulative sedimentation during non-flood season. Different water levels operations and reservoir flow processes have different sediment flushing effects. In view of the differences in the sand discharge process of Sanmenxia Reservoir, statistical characteristics of sediment discharge in flood season since SCWDMF were adopted to analyze the influence of reservoir open discharge and water level operations on sediment discharge. The results show that under the operation of normal water lever of 305m and open discharging in flood period, sediment discharge has the characteristics of more coming and more discharging, and the total amount of sediment discharge in flood season is closely related to the incoming runoff and sediment concentration; When the reservoir is fully ungated discharging, reservoir scour depends on the flow rate and the open duration, with the net efficiency of sediment discharge decreasing with the flow increase and open duration extension; When the water level is controlled between 305-311m, sediment discharge occurred as the flow is above 1000m3/s with the efficiency depending on the retention time of the sediment-laden flow in the backwater section and the ratio of the inflow and outflow discharge. This research provides basis for the optimization of Sanmenxia Reservoir operation. © 2021, China Water Power Press. All right reserved.