Hydropower vulnerability to drought-flood abrupt alternation under climate change

Drought-flood abrupt alternation (DFAA) events, characterized by swift transitions between hydrological extremes, pose critical challenges to reservoir management and hydropower generation. This study employs global hydrological simulations and a relative impact index to investigate the spatiotemporal characteristics of DFAA events, including flood-to-drought (FDT) and drought-to-flood (DFT) transitions, along with their effects on global hydropower generation. The results indicate that DFAA events are widespread, with FDT and DFT occurring on average 3.51 and 4.85 times per decade, respectively, and becoming increasingly frequent under climate change, particularly in East Asia and Europe. These events typically cause more severe hydropower shortages than single droughts or floods. FDT and DFT events reduce hydropower generation by 11.53 % and 9.16 %, respectively. Moreover, hydropower plants with high regulation capacity show stronger resilience in DFAA events, with their proportions of being less affected in FDT and DFT events being 6.7 % and 14.3 % higher than those with low regulation capacity, respectively. The influence of DFAA on hydropower generation arises from the evident disparity in reservoir management, where abrupt transitions between drought and flood conditions hinder the ideal scheduling of water storage and release, hence constraining hydropower generation. These findings highlight the need to explicitly incorporate compound event risks into reservoir operation strategies to better secure hydropower supply under future climate uncertainty.