Joint optimal flood control operation of the Jinsha River Downstream-Three Gorges cascade reservoirs based on flood control water level

The successive construction and operation of large-scale reservoirs in the upper Yangtze River have substantially altered the spatiotemporal characteristics of flood events and the river hydrological regime. Given the prevailing constraints imposed by the flood limit water level (FLWL) on the comprehensive operational benefits of reservoir groups, as well as the insufficient validation of joint flood control operation based on the flood control water level (FCWL), three joint flood control operation schemes were developed for the Jinsha River Downstream-Three Gorges cascade reservoir group. Flood control safety was evaluated and verified based on design flood estimates during the Three Gorges Reservoir (TGR) operation period. Furthermore, numerical simulation and operational regulation were performed using daily discharge data for the flood season from 1990 to 2025. The results indicate that the maximum flood regulation water levels of the TGR based on the FCWL scheme are 168.21 m, 167.28 m, 169.16 m, and 171.56 m, 170.36 m, 171.45 m for the 100-year and 1000-year design flood hydrographs amplified by 1954, 1998, and 2020 three typical years, respectively. All simulated water levels are lower than the current regulatory thresholds, namely the highest flood regulation water level of 171 m and the design flood water level of 175 m, which maintains a sufficient flood prevention safety margin. The proposed joint flood control operation scheme for cascade reservoir groups based on FCWL can generate an additional average annual power generation of 7.32 billion kW∙h during the flood season, representing a 5.41% increase. The multi-objective optimal regulation scheme further enhances flood control performance. The findings confirm that the FCWL scheme can significantly improve the comprehensive utilization benefits of cascade reservoir groups while fully ensuring flood control safety.