Research on reverse order impoundment mode of cascade reservoir flood control system: Case study on upper reaches of Yangtze River

Abstract

Flood control in the Yangtze River Basin has always been a thorny issue in Chinese history. Along with the development of water science and technology, a large number of reservoirs have been constructed in the Yangtze River Basin, especially the progress of the reservoir operation theory, the joint flood control simulation and decision-making of reservoir groups has been applied extensively, which proved an effective way to reduce the flood risks and losses in the middle and lower reaches of the Yangtze River Basin. However, an increase in the constraints of the reservoir operation (or a single reservoir becoming a multiple-reservoir system) results in an exponential increase in the computational dimensions of the joint flood control simulation, often referred to as the 'curse of dimensionality'. Therefore, based on the aggregation-decomposition (AGDP) method, this paper proposes a cascaded reservoir group integrated operation mode, namely, the 'reverse order impoundment method of cascade reservoir' (ROIMCR) mode, and adopts the improved artificial bee colony (IABC) algorithm to solve the optimization problem of the ROIMCR mode (IABC-ROIMCR) and establish an optimal operation model for cascade reservoir joint flood control. The results show that: 1. With the 'conventional operation' (CO) mode, the ROIMCR mode has more advantages, the average peak flow reduction rate with 32.89% is higher than that of the CO mode 2.91%. 2. In solving the flood optimization operation problem of the cascade reservoir system, the application of the IABC algorithm can effectively reduce the dimensions in the mathematical mode, and has evident effects. The average peak flow reduction rate in the IABC-ROIMCR mode is 44.87%, and 14.89% higher than those of the CO mode. 3. With the IABC-ROIMCR mode, the flood crest standard of cascade reservoirs can be reduced from a 100-year return period to less than a 5-year period, and the flood crest standard of the Lizhuang Hydrological Station from more than a 50-year return period to less than 5-year period. The flood crest standard of the Zhutuo Hydrological Station can be reduced from a 100-year return period to approximately a 5-year period, thereby greatly improving the flood control standard in the upper and middle reaches of the Yangtze River Basin. In addition, the peak inflow to the Three Gorges Reservoir is reduced, and as a result, the flood control pressure in the lower reaches of the Yangtze River Basin is alleviated to a certain extent.