Flood Control Capacity of the Three Gorges Project for Different Frequency Floods

An accurate assessment of flood control capacity of a reservoir is a prerequisite for ensuring the safety of flood control works. This study used the method of adding side reservoirs and used MIKE11 to establish a one-dimensional hydrodynamic model of the Three Gorges Reservoir (TGR). Based on the combination of the dynamic reservoir capacity flood control and the separation of the outflow of the Jingjiang Three Outlets, the flood control capacity of the TGR was assessed. The results showed that the TGR can effectively withstand large floods below the magnitude of 100-year return period discharge. For a rare flood event in 1,000 years recurrence interval, it is necessary to use the Jingjiang flood diversion area for ensuring the safety of downstream floodplains along the main river course. As far as exceptionally large floods with the return frequency of 0.01% or lager magnitude concerned, this extreme high flow cannot be safely impounded by the TGR even if the Jingjiang flood diversion area is adopted. Therefore, a series of upstream cascade reservoirs are suggested to be fully utilized for a joint flood control strategy.