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Sacramento River Ecological Flows Tool (SacEFT): record of design (v.2.00)
With over 50 years of international concern about the effects of flow alteration on ecosystems, the continued advancement of scientifically based tools to quantify the ecological effects of flow regulation and river channel alterations has become a prominent research activity (e.g., Stalnaker 1994; Bunn and Arthington 2002; Annear et al. 2004; Veldkamp and Verburg 2004; Arthington et al. 2006; Poff et al. 1997; Petts 2009; Poff and Zimmerman 2010). Process-based models constitute one powerful and efficient tool for comparing the effects of alternative flow and river channel change scenarios. The Sacramento River Ecological Flows Tool (SacEFT) is a decision support tool emphasizing clear communication of trade-offs for key ecosystem targets associated with alternative conveyance, water operations and climate futures in the Sacramento River eco-region. The vision for SacEFT, one we believe we have achieved, is to create software that makes it easy for non-specialists to expand the ecological considerations and science foundation used to evaluate water management alternatives on the Sacramento River. Practical integration of multi-species, multi-habitat needs in the evaluation of water operation scenarios is challenging. In SacEFT, we more transparently relate additional attributes of the flow regime to multiple species’ life-history needs, thereby contributing to a more effective understanding of water operations on representative sets of focal species and their habitats (Chinook salmon, steelhead, green sturgeon, bank swallows, channel erosion/migration, Fremont cottonwoods, and large woody debris recruitment). Scientifically, SacEFT takes a bottom-up, process-based approach to the relationship between flow and related aquatic habitat variables, and looks at how these variables are tied to key species life-stages and ecosystem functions. Our work and the input of many expert contributors develops a more complete understanding of the flow regime and its relation to natural processes and species’ requirements, so as to identify the critical attributes of the flow regime necessary to maintain ecosystem function. The multi- species, multi-indicator paradigm provides a “portfolio” approach for assessing how different flow and habitat restoration combinations suit the different life stages of desired species. In so doing, SacEFT transparently relates additional attributes of the flow regime to multiple species’ life-history needs in an overall effort at careful organization of representative functional flow needs. This provides a robust scientific framework to focus the definition of ecological flow guidelines and contribute to the understanding of water operation effects on focal species and their habitats. The performance indicators and functional relationships built into SacEFT were vetted through two multi- disciplinary workshops and numerous design document reviews. The recommendations of these technical design workshops and subsequent peer reviews provide the basis for the indicators and models described in this document. Collectively, the constituent focal species “submodels” provide twelve (12) performance measures which vary in spatial scale, temporal scale, and levels of reliability. Multi-year roll-ups allow users to quickly zoom in on the much smaller set of performance measures which differ significantly across management scenarios. With the completion of SacEFT v.2, the decision analysis tool provides the ability to: 1. improve the basis for evaluating flow alternatives on the Sacramento River from Keswick to Colusa (e.g., Bay-Delta Conservation Plan flows, North-of-Delta Off-Stream Storage Investigation, Shasta Lake Water Resources Investigation, and other future diversions and water transfers); 2. evaluate a variety of management actions’ affects (e.g., gravel augmentation and bank protection alternatives) on ecosystem targets for the five Sacramento River focal species; 3. provide multiple levels of communication of information ranging from simplified formats for managers and decision-makers to in-depth displays of detailed functional relationships and transparent assumptions for review by technical experts; 4. leverage existing systems and data sources (CalSim /USRWQM/USRDOM, historical gauging station records, the Meander Migration Model, and TUGS, a new sediment transport model); and 5. catalyze exploration of new alternatives as data sets become available (e.g., climate change) and help promote the development of needed flexibility in the water management system. By leveraging many of the same planning models used in existing socioeconomic evaluations in California (e.g., CalSim, USRDOM, USRWQM), SacEFT provides an “eco plug-in” for water operation studies based on use of these physical hydrologic/water balance models. SacEFT advances and enables ecological flow (e-Flow) science by linking these physical models to a representative set of individual ecosystem components inside an overall compressed, cross-disciplinary synthesis tool for evaluating conveyance operation alternatives in the Sacramento River eco-region. Lastly, SacEFT’s output interface and reports for trade-off analyses make it clear how actions implemented for the benefit of one area or focal species may affect (both positive and negative) another area or focal species. For example, we can show how altering Sacramento River flows to meet export pumping schedules in the Delta affects focal species’ performance measures in the Upper and Middle Sacramento River. One of the biggest challenges in the practical implementation of ecological flow guidelines is the wide range of objectives, focal species and habitat types that need to be considered. Our work to date has brought into focus how these various objectives cannot all be simultaneously met. In nature, conditions often benefit one target or species to the potential detriment of another in any given year. Fortunately, flow characteristics that benefit the various ecological targets investigated are usually required on a periodic basis and not every single year. EFT studies simplify communication of these trade-offs, and catalyze definition of state-dependent management practices that promote the development of needed flexibility in the water management system. Building a tool that makes accurate future predictions of ecosystem behavior is challenging and usually not possible in complex, open natural systems (Oreskes et al. 1994). SacEFT’s main purpose is to characterize and explore important ecological trade-offs and inform managers and decision makers about the relative impacts of various flow management alternatives. The system can also act as a catalyst for exploring deliberate or opportunistic adaptive management experiments (Murray and Marmorek 2003) that assess actual ecological responses on a variety of spatial/temporal scales. This approach (model exploration of management alternatives and adaptive management experiments) will ultimately help water resource managers and stakeholders converge on options that best strike a balance among various of conflicting objectives.