The Yolo Bypass is one of two flood bypasses in the Sacramento Valley located in Yolo and Solano Counties and protects Sacramento and other riverside communities from flooding through a system of weirs. Flood control is the main purpose of the Yolo Bypass and is crossed by the Yolo Causeway. Shot - March 15, 2009. Photo by Steve Payer/DWR

SCIENCE SPOTLIGHT: Yolo Bypass floodplains and fish food

The Yolo Bypass was originally designed as a flood control measure to protect the city of Sacramento.  It is also widely viewed as an environmental and water management success story, as it has been demonstrated to achieve multiple benefits, including benefits to agriculture, flood control, and the environment that derive from reestablishing the connectivity of a major river to its floodplain.

Previous reports have highlighted studies that document some of the environmental benefits.  In a study referred to as the Nigiri project because of its benefits for both rice and fish, researchers funded by the Delta Stewardship Council, Department of Water Resources, and others demonstrated that managed inundation of the Yolo and Sutter bypasses at times not necessarily needed for flood control resulted in the generation of large amounts of fish food, zooplankton and higher growth rates and larger sizes of juvenile Chinook salmon that were using the floodplain for foraging and shelter.

These outcomes can positively impact fish because larger juvenile salmon have a higher chance of survival when they migrate to the ocean.  But questions remain about the potential benefits of managed floodplains for fish populations and food webs at a larger scale beyond the scale of the floodplain itself or the fish that use that particular habitat.

At the May meeting of the Delta Stewardship Council, Delta Lead Scientist Dr. Laurel Larsen spotlighted two recent studies from Dr. Carson Jeffres’s lab at UC Davis, which the Delta Stewardship Council funded to address these questions.  The studies are relevant to science action 3-D in the 2022 to 2026 Science Action Agenda, which is to test and monitor the ability of tidal, non-tidal, managed wetlands and inundated floodplains to achieve multiple benefits over a range of spatial scales.  These studies are also relevant to the amended chapter four of the Delta Plan, for which the second core strategy is restoring ecosystem function, specifically calling for functional floodplains.

In the first study, Floodplain trophic subsidies in a modified river network: managed foodscapes of the future?, led by Anna Sturrock, the research team sampled zooplankton and Chinook salmon in different parts of the Delta, including the areas within and downstream of the Yolo Bypass and Cosumnes River.  The Cosumnes River was included because it has no dams across it, so it naturally inundates its floodplain in the wet season of most years.

From the samples that the researchers took, they identified the types of zooplankton found and dissected the guts of the salmon to identify their contents.  As expected, they found that the large-bodied zooplankton that typify floodplains, also known as cladocerans, constituted the largest food source for salmon, just below the floodplain and particularly during the wet years, as shown in yellow on the graph at the lower right of the slide.

During those wet years, they found that the same was true for salmon captured even in the West Delta and Chipps Island, well downstream of the source floodplains.  For those zooplankton, salmon stomach fullness tended to correlate with the number of cladocerans they consumed and were likewise highest during wet years when floodplains are inundated.  So collectively, these findings show that floodplain inundation benefits food webs and fish well beyond the immediate scale of the floodplains.

In the second study, Multiple trophic pathways support fish on floodplains of California’s Central Valley, led by Bobby Nakamoto, poorly understood food sources (other than zooplankton) originating from inundated floodplains and wetlands were evaluated for their impacts on fish.  In particular, there have been many questions in the science community about the extent to which the breakdown of detritus, or partially decayed organic matter from plant material, is the foundation of Delta food webs compared to algae typically associated with open water areas.  Now, using relatively new methods, scientists can identify the original source of the amino acids that are the building blocks of proteins found within the tissues of fish collected from the Delta and whether those amino acids originally came from algae or detrital food sources.

Ground view of the Yolo Bypass and the Vic Fazio Wildlife Area. In the foreground are massive rice fields that form a valuable wetland habitat to a wide variety of fowl. Photo by Steve Payer / California Department of Water Resources

“In this study, the research team applied this approach to trace the amino acids from tissues of Chinook salmon, rainbow trout, and American shed, and they quantify the extent to which these originated from different possible sources, including algae, bacteria, and fungi, which break down detritus, and plant materials,” said Dr. Larsen.  “Findings indicated that while algae was the main basal food web source of amino acids within the tissues of most consumers, bacteria, fungi, and plant material were the main sources for some individuals.  And in addition, there was strong evidence that bacteria and fungi serve as important secondary basal food web sources across the tissues sample.”

“So collectively, these two studies highlight the potential for the accumulation of multiple benefits for food webs that result from the reconnection of channels to floodplains and wetlands.  Not only do such actions generate food for native fish within and downstream of these landscape features, but they can also supplement detritus production with cascading impacts up through the food chain.  So this new understanding will help us better account for the quantification of benefits associated with floodplain and wetland restoration and tidal reconnection.”

Community Surface Dynamics Modeling Systems Workshop

Dr. Larsen attended the Community Surface Dynamics Modeling Systems Workshop in Boulder, Colorado.  Scientists from around the world attended the meeting.  Dr. Larsen gave the opening plenary for the meeting, which aimed to advance accessible, reproducible, interlinkable modeling tools for the earth surface processes community, similar to the Delta science collaboratory that has been under discussion for some time.

“This year’s meeting had a theme of patterns and processes across scales, so I chose to focus my remarks on the need for establishing agency academic community partnerships in the practice of modeling to develop resource management strategies that promote resilience in the face of climate change,” she said.  “More specifically, I spoke of how the inclusion of diverse communities of people affected by the outcome of management decisions can help produce consensus, new networks of communication, compromise, and trust.  I used the Franks Tract Futures Project as an example of the potential of this approach at small scales and highlighted the multi-benefit wetland restoration design that emerged from that project.  It has been very influential and thinking about how the Delta might adapt to climate change.”

“I also talked about how a process of coproduction was embraced in our Delta Adapts initiative.  I then discussed some of the challenges and needs associated with scaling this type of approach up regionally to the Delta and then, frankly, to the state, which is so strongly impacted by resource management decisions in the Delta.  I concluded by presenting the initial proposal for a collaboratory that emerged from a group of UC CSU agency partners following the integrated modeling framework meeting.  And I got a lot of positive feedback about the talk, as well as some additional ideas for pursuing competitive funding opportunities for elements of the collaboratory.”

I also attended a fantastic clinic provided by a faculty member at Northeastern University that highlighted a new open source tool for participatory modeling.  It’s definitely something we could adopt for processes like Delta Adapts or some of the projects that we’re developing in association with the salinity management workshop series.  And I look forward to sharing what I’ve learned with staff soon.”

Adaptive Management Forum

The Adaptive Management Forum, held in early May 2023, is a biannual meeting called for in the Delta Science Plan and the Adaptive Management Review by the Delta Independent Science Board.  The theme of this year’s meeting was governance for adaptive management, and it was well attended.

Delta Stewardship Council Chair Virginia Madueno provided the opening remarks.  Later in the morning, Council Member Diane Burgis presented on governance needs for equitable adaptation in a dramatically changing Delta watershed focusing on how equity and governance support better adaptation.  She highlighted the success story of the Dutch Slough restoration project that engaged and enriched the whole community, including its youth.  Those themes echoed through the entire program, which included storytelling and panel presentations from community representatives not typically given a platform at government meetings, including the Stockton poet laureate, members of Restore the Delta and Little Manila Rising, who called for the engagement of youth in adaptive governance processes, and tribal representatives who called for the need to engage communities early in project planning processes, which echoes some of what was heard in the tribal listening session last month.

Some of these key themes and takeaways were that building relationships and trust is key; adaptive management is constrained under the current government system; there’s a need for strategic instead of reactive adaptation planning; there’s a need for better funding and improved data collection and sharing; there’s a need for coalition building and collaboration.  Dr. Larsen noted that there is a more thorough presentation on the workshop that was presented at the April Delta Independent Science Board meeting.

Part two of the Adaptive Management Forum will take place on June 27 and will feature interactive activities and discussions intended to continue the conversation around inclusive and equitable governance for adaptive management.  Click here to attend in personClick here to attend via Zoom.

California Water and Environmental Modeling Forum Annual Meeting

The California Water and Environmental Modeling Forum convened its 29th annual meeting on April 17-19.  CWEMF was founded to facilitate an open exchange of information on California water issues, resolve technical disagreements in a non-adversarial setting, and ensure that technical work considers the needs of stakeholders and decision-makers.

Dr. Larsen attended that meeting to network and advance the planning of the modeling collaboratory.  Dylan Stern represented the Council with a presentation on Council-funded research and modeling.  The key takeaway from Dylan Stern’s presentation was that the Council’s investments in modeling biogeochemistry and ecological dynamics are paying dividends.

The modeling community has embraced linked hydrodynamic biogeochemical models, which are close to becoming tools used in real-time operations to better manage nutrients, aquatic vegetation, and other constituents.  Some models were used to estimate the potential effects of upgrading the Sacramento Regional Sanitation District’s wastewater treatment plant.  With the completion of that project, the science community is now beginning to witness the outcomes of the Science Program’s investment in high-frequency data collection.  Those investments and some resulting datasets can and will continue to be leveraged to improve models for other imminent resource management needs, including better managing harmful algal blooms and informing restoration management, climate change resilience, and future infrastructure projects.

Decision-making Under Deep Uncertainty seminar series continues

The second webinar of the Decision-making Under Deep Uncertainty seminar series, sponsored by the Delta Independent Science Board, will occur on June 14 at 1pm.  The seminar as a whole is going to focus on available tools for decision making under deep uncertainty and their applications in California.

The webinar will feature Robert Lempert, principal researcher at the RAND Corporation and director of the Frederick S. Pardee Center for Longer Range Global Policy and the Future Human Condition.  Andrew Schwartz, the State Water Project Climate Action Coordinator for the California Department of Water Resources, will also speak about some of the risk management approaches the Department of Water Resources uses.  Register to attend in personRegister to attend virtually.

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