Regulated rivers worldwide are managed to meet human water demands, but resulting flows often fail to support hydrogeomorphic processes and other downstream ecosystem needs. This failure is highlighted in California's Sacramento-San Joaquin River watershed where complex and decentralized water management regimes confound efforts to balance co-equal management goals of supplying agricultural and urban water demands with maintaining ecosystem functioning. As California struggles to meet competing demands for scarce water, water managers are increasingly required to provide environmental flows in the right place, at the right time, and in the right amount. We present the framework for getting "more pop per drop" in environmental flow management by focusing on a 'functional flows' approach, which emphasizes process-based hydrograph components to guide management of regulated river systems. Key flow regime components like peak magnitude flows, dry-season low flows, wet-season initiation flows, recession flows, and interannual variability are indexed against key history strategies of focal species such as salmonids and other native fishes. These framework principles are a guide to selecting hydrograph components, acceptable ranges of variability, and meaningful flow portfolios to meet ecosystem needs. While the Sacramento-San Joaquin River offers an important use case, application of this framework, which connects natural flow regime components to specific biophysical riverine functions, can inform water resource management strategies and environmental flow requirements globally. This is important because hydropower dams are expected to more than double over the next 15 years globally, and thus water management strategies that balance ecosystem needs with human demands are urgently needed.
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