Scheduling strategies of cascade reservoirs under extreme drought conditions during the impoundment period: A case study of lower Jinsha River, China

Cascade reservoir system, lower Jinsha River Basin, China. Influenced by global warming, the Jinsha River Basin experiences frequent extreme droughts. Notably, the most severe drought since 1961 occurred July-August 2022, causing critical storage deficits. To address severe drought impacts on cascade storage and power supply, a multi-objective optimal operation model was developed. It aims to maximize both impoundment efficiency (IE) at the end of impoundment period (IP) and total power generation benefits across impoundment, high water level operation, and drawdown periods. Energy storage (ES) at the end of IP served as an intermediate variable enabling coordinated multi-stage optimization, mitigating risks of compromising long-term benefits from single-stage optimization. Under the optimal operation scheme for the 2022 impoundment period, an impoundment efficiency (IE) of 0.784 was achieved, and total power generation over the three periods reached 133.809 billion kWh, including 11.169 billion kWh during impoundment. The trade-off between IE and generation benefit loss was quantified. Analyzing the 2022 extreme drought scenario, the optimal reservoir filling sequence was determined as Wudongde-Baihetan-Xiluodu-Xiangjiaba. Reducing IE to maximize contemporary generation increases short-term output but compromises overall benefits across the full cycle. Thus, prioritizing higher IE is crucial for safeguarding total generation benefits. Optimized electricity pricing may partially offset benefit losses under extreme conditions. • The optimization model links impoundment period with subsequent period benefits. • Energy storage is introduced as an intermediary variable in the optimization model. • The storage sequence of cascade reservoirs under extreme drought is determined. • The calculated compensation electricity price provides a theoretical basis for scheduling.