Dams alter flow regimes, fragment rivers, and harm freshwater ecosystems (Munsch et al. 2022; Barbarossa et al. 2020). Yet, freshwater ecosystems are increasingly dependent on surface reservoirs for environmental flows and suitable water temperatures as rivers have become irrevocably altered by water development, consumptive water uses, land use change, and climate change (Grantham et al. 2020; Yarnell et al. 2020). This creates a paradox where dams have contributed to freshwater ecosystem decline, but are now instrumental for managing environmental water and enhancing downstream ecosystems.