Timing is everything: Rethinking flexible hydropower operations for the economy and environment

Abstract Hydropower facilities can alter river flow regimes, leading to ecological degradation and conflicts between revenue generation and ecological objectives. This study develops a new and unique framework (FREE—Flexible Releases for Economics and the Environment) for hydropower management that uses operational flexibility to balance economic and ecological objectives that are, respectively, maximized through unrestricted hydropeaking and maintaining natural flows. FREE integrates flexibility by permitting reservoir releases to deviate from inflows when power generation is most economically valuable. Operational flexibility is characterized by the magnitude and frequency of deviations from an inflow‐equals‐outflow (IEO) regime and is applied seasonally to reflect varying economic and ecological needs throughout the year. FREE is implemented using an optimization model applied to three hydropeaking facilities on the mainstem Connecticut River that are currently in a relicensing process. Estimated impacts of operational flexibility are quantified on annual and seasonal scales, with economic goals measured by power and revenue, and ecological goals by a proxy measure: the Richard‐Baker flashiness (RBF) index. To explore operational flexibility, two inflow regimes are investigated: existing inflows, which are altered by upstream hydropower operations, and estimated unaltered inflows. FREE was presented to interested parties engaged in the Connecticut River relicensing process, where it was applied in collaborative negotiations designed to develop integrated, dynamic, economically viable, and ecologically supportive hydropower operations. Trade‐offs between estimated revenue generation and RBF, as applicable to these interested parties, were presented along a Pareto frontier.