Hydropower, which has long been recognized as an effective and reliable source of renewable energy, accounted for 70% of total renewable energy production in 2016. In addition to provision of clean renewable energy, large hydropower systems are often operated on a long-term schedule with multiobjective requirements such as maintaining flood control, water supply, navigation, and ecological protection (Liu et al., 2020;Xu et al., 2015Xu et al., , 2020. In recent years, following the rapid development globally of intermittent renewable energy sources (e.g., wind and solar energy) to address degraded environmental quality and problems associated with climate change, operation of hydropower systems must now incorporate new tasks associated with integration and stabilization of the uncertain energy production by these intermittent renewable sources (Liu et al., 2019). To enhance comprehensive benefit through delivery of water and energy to the multiobjective demand side, joint operation of reservoir systems with capability to coordinate spatiotemporal water release and water head is essential to resolve conflicts regarding the allocation of water and energy resources to competing demands. In practical application of realtime hydropower operation based on forecasts, one of the most critical challenges in informing multiobjective and joint reservoir operation is how best to make efficient and robust decisions under the condition of uncertainty owing to incomplete knowledge and inaccurate forecasts, such that negative consequences of imbalanced demand and supply are manageable and expected returns or costs are acceptable (Roach et al., 2016).Forecast errors are widely recognized as the primary factors affecting the reliability of hydropower operation strategies (Xu, Liu, et al., 2021), especially in the long-term planning horizon, because forecast models have inherent uncertainties attributable to their input, structure, and parameters in addition to errors associated with human-induced impression or fuzziness (Li et al., 2011;Mo et al., 2021). Under the perturbation of error sources,