Reservoir operation strategies to mitigate hydrological drought effects along the middle and lower reaches of the Yangtze River

Study region: The middle and lower reaches of the Yangtze River Study focus: Reservoir operation strategies to help alleviate downstream water-levels decline are crucial for water resource management under drought conditions. A framework of reservoir operation strategies to mitigate hydrological drought effects for downstream rivers is proposed in this study. Firstly, river water level simulation (RWLS) models that consider the impact of upstream reservoir release was established based on the LSTM method. The impact of reservoir operation decisions on the downstream river water levels by combining the output from the reservoir system with the input of RWLS model was then analyzed. Finally, the influence of drought mitigation strategies on the operating process and hydropower generation benefit of the reservoir itself has been analyzed. New hydrological insights for the region: The results reveal that (1) the proposed RWLS model considering information about upstream reservoir releases and upstream river station water levels outperforms the traditional data-driven model, with Nash-Sutcliffe efficiency coefficient of greater than 0.97 for the water level forecasting at four hydrological stations; (2) the implementation of reservoir operation for mitigating drought effects during the flood season sacrifices more benefits of hydropower generation than that during dry seasons; (3) the larger the water replenishment flows and the longer the duration of drought mitigation operation, the larger the loss of reservoir system's hydropower generation.