The State Water Resources Control Board, which both allocates surface water rights and protects water quality for people and wildlife, is proposing a new approach to setting flow standards in the Sacramento-San Joaquin River Delta.
The Delta drains about 40 percent of California, including much of the Sierra Nevada, and supplies fresh water to two-thirds of the state’s population and millions of acres of farmland. This water hub is also home to hundreds of native species as well as a migratory corridor for salmon and birds.
Under the existing approach, the State Water Board establishes the Delta inflow and outflow standards designed to protect fish and wildlife. Under the new approach—called voluntary agreements—these Delta flows would be determined collaboratively by government agencies as well as by the local water agencies that supply users.
Voluntary agreements would also require restoring habitats that fish depend on, including spawning grounds and floodplain nurseries, as well as improving fish passage. The thought is that a combination of flows and high-quality habitat can do more for fish than flows alone. “The agreements aim to improve conditions and help change the trajectory of declining native fish species in the Delta and the rivers that flow into it,” according to the California Natural Resources Agency.
The hope is that voluntary agreements will allow the State Water Board to finally update the Bay-Delta Water Quality Control Plan, a federally required effort that began in 2009 but has been hampered by a barrage of lawsuits from, for example, Central Valley irrigation districts, the City of San Francisco, and the U.S. Department of Justice and U.S. Department of the Interior.
Voluntary agreements for the Delta would entail integrating flow with habitat restoration to benefit imperiled fish. The estimated $2.6 billion cost of implementing these agreements would be shared by water users and the state and federal governments. Implementation includes governance and habitat monitoring to analyze outcomes and manage adaptively for eight years, at which point the parties would decide whether or not to continue the program.
In January 2023, the State Water Board released a new draft report on the scientific basis for voluntary agreements in the Delta to supplement their 2017 report.
In March 2023, the Delta Independent Science Board (ISB) submitted comments on the scientific basis for voluntary agreements in the Delta. The Delta ISB—which includes 10 scientists from across the United States with expertise ranging from fish ecology to river ecosystems to environmental decision-making—is charged with evaluating scientific programs that support adaptive management of the Delta.
Adaptive management is a science-based approach to making environmental decisions in the face of uncertainty. This strategy for managing natural resources is inherently experimental, relying on monitoring and evaluation of outcomes to learn the best ways of refining future management decisions.
The State Water Board’s 2023 draft scientific basis report acknowledges the uncertainty in the science of voluntary agreements in the Delta, and outlines an accompanying adaptive management plan.
To learn more about the Delta ISB’s assessment of the scientific underpinnings of voluntary agreements in the Delta, Robin Meadows spoke with Lisa Wainger, a University of Maryland environmental economist who chairs the Delta ISB.
What would the Delta ISB most like to see in voluntary agreements going forward?
First and foremost, we want to see the adaptive management experiment done well because we know this is going to be extremely hard. There’s so much natural variability in the system, from weather extremes to changes in the crops grown on land to conditions in the ocean, which affect adult salmon.
It’ll be key to have proper monitoring and to track whether things are moving in the right direction. Monitoring tends to get short shrift and this is a case where it will be critical—fish respond to almost everything in the water and on the landscape.
Another need is the right mix of expertise on the adaptive management team, and to have them be dedicated to the project. They need to have enough time for it and to be there consistently instead of going through a revolving door. It will be important to keep institutional knowledge about prior system responses to management when interpreting the data and adapting to changes.
What are other key ways the scientific underpinnings of voluntary agreements could be strengthened?
Both flow and non-flow changes need to be assessed to ensure that they are performing as anticipated to improve habitat and fish outcomes. The habitat restoration plans and assessments should address whether adjustments are needed for climate change, especially higher water temperatures that could be detrimental to salmon and smelt.
Understanding multiple sources of stress, and how they may combine, improves the ability to design restoration that leads to successful outcomes for fish, particularly since changes and restoration will impact different species to different degrees. Success means not only increasing abundances of the targeted fish but also in providing ecological conditions that support a resilient aquatic system.
Ultimately, achieving the benefits from restoration will require substantial and diverse restoration efforts. In the current plan, not all habitat goals are met in all tributaries. It’s important to keep the scale of restoration big to see big effects. This has the added benefit of creating spatial redundancy, so that you’re literally not putting all your eggs in one basket.
Finally, there are only two check-in points, one at four years and another starting in the sixth year, after which they’ll decide whether to continue the voluntary agreements. These assessments need more specifics—they need to set performance measures and thresholds of concern for multiple environmental indicators such as fish abundances, growth rates and condition as well as habitat variables including temperature and water quality.
Some environmentalists say that voluntary agreements trade flows for habitat restoration, and that this is flawed because the former have proven benefits to fish but fish benefits from the latter are anticipated but as yet unproven. What is the Delta ISB’s “big picture” take on the science side of voluntary agreements in the Delta?
The science of combining flows with habitat restoration is uncertain and some would say we should stick with what works, which is flows. But just focusing on flows is also uncertain. This is because this approach entails mimicking historic flows in a system with a host of new stressors such as rising water temperatures, disconnected flood plains, and invasive species that may have changed food availability or fish interactions such as predation of native species. Flows are just one of the many factors that can affect fish productivity.
Flows are one of the main environmental variables that affect fishes, and this is one of the drivers that we have some ability to control. Habitat restoration is also a management tool that can support fish populations, if done properly. Scientifically, considering both of these in the same equation is more robust than single driver approaches.
Doing voluntary agreements as an adaptive management experiment will be a test of whether a combination of improvements in flow and non-flow habitat—such as marshes and accessible floodplains—can increase native fish populations. The difficult challenge is that to have healthy fish populations, you have to address all the bottlenecks at every life stage: spawning, hatching, young and adults, which require different habitats at different times.
Flows are important for some life stages, including migration and rearing, and can improve water quality, but other parts of the system could be limiting for other life stages. The voluntary agreements propose to create habitat for different life stages. For example, floodplains provide rearing habitat, and marshes support young fish by providing more food.
The voluntary agreements are a complex undertaking, with significant opportunities for learning how to effectively improve the Delta’s aquatic habitat, but only if they are implemented well and the adaptive management is thorough.