Sacramento River Ecological Flows Tool (SacEFT): record of design (v.2.00)

Abstract

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.