Boosting hydropower generation of mixed reservoirs for reducing carbon emissions by using a simulation-optimization framework

The optimization operation of reservoir seasonal flood-limited water levels (FLWLs) can counterbalance hydropower generation and flood prevention in the flood season. This study proposes a multi-objective optimization operation model to optimize the reservoir seasonal FLWLs for synergistically maximizing hydropower benefits and reducing flood risk. The mixed reservoirs composed of the Three Gorges Reservoir and six other reservoirs located in the upstream Yangtze River of China constitute the case study. The results showed that (1) compared with the annual FLWL scheme, the best solutions without lowering flood prevention standards could increase the seasonal FLWL values of the seven reservoirs from 1.39 to 6.51 m in the pre-flood season, from 0.13 to 1.53 m in the main-flood season, and from 0.76 to 4.36 m in the post-flood season; (2) the proposed seasonal FLWL schemes without increasing flood prevention risk could facilitate the joint operation of the mixed reservoirs to achieve 868 million kW h (5.1% improvement) in average hydroelectricity production during the flood season, meanwhile reducing 681 million kg CO2 emissions accordingly. The results support that the proposed methods can boost hydropower production to benefit China's national tactics in accomplishing peak carbon dioxide emissions before 2030.