Since its launch in 2004, the Ecological Flows Tool (EFT) project has had the goal of improving water planning by explicitly linking ecosystem needs with physical models in the Sacramento River and the San Joaquin-Sacramento Delta. Aided by over 70 scientists and managers, we have developed an integrated bio-physical decision support tool that characterizes how a suite of 13 focal species (and habitats) are expected to respond to alternative flow, river bank, and gravel management scenarios.

EFT peer reviewed species sub-models are made up of 25 key life-history indicators, each of which is driven by relevant measures of flow, water temperature, channel migration, salinity and/or stage at a daily timescale. Our research has clearly demonstrated that there is a pressing need to develop greater awareness of the value of flexibility to manage ecosystem trade-offs over time within and among objectives.

The detailed applications of EFT crystallize the fact that it is impossible to achieve all ecosystem objectives – let alone the co-equal goals of meeting human, agricultural and environmental needs – each and every year. We describe a paradigm shift which involves seeing balance as a condition which does not involve the same species or objectives losing (or winning) unnecessarily often.

Other findings highlight the need for a stronger focus on climate change mitigation itself (and the general difficulty of comparing future scenarios to a progressively deteriorating baseline). Our work also reveals promising results on how EFT flow criteria can be used to create new rules for other hydrosystem models (e.g., CALSIM) to improve outcomes for endangered species.

With its emphasis on specific cause-effect linkages based on functional flow needs, EFT provides a solid framework that remains open to testing, enhancement and adaptation over time.

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