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Joint SWC/DWR Funded Research Sheds New Light on Endangered Chinook Salmon on the Sutter Bypass
Joint SWC/DWR Funded Research Sheds New Light on Endangered Chinook Salmon on the Sutter Bypass
18 June 2019

Findings Reveal More Dynamic Floodplain System than Expected with Implications for Habitat Restoration and Species Management

Sacramento, CA – The State Water Contractors (SWC) partnered with the California Department of Water Resources (DWR) to fund research that provides new insight into the life cycle of Chinook Salmon on the Sutter Bypass — an area that has received little attention from researchers in the past but is inviting more attention in light of recent findings.

SWC contributed $115,000 for this research, and DWR provided matching funds for the first $100,000, bringing the total investment to $215,000. Scientists at University of California, Davis and University of California, Santa Cruz performed the research from March 2018 through March 2019. Results of the research are expected to better inform fish and water management actions that have the potential to protect fish from Butte Creek and the Sacramento River watershed, while also improving water supply reliability for people.

“Every day, we are making new scientific discoveries that challenge our assumptions and advance our understanding of how to restore habitats in a meaningful and responsible way,” said Jennifer Pierre, SWC General Manager. “There are many factors that must come together to provide a habitat that supports the unique needs of the fish on the Sutter Bypass. We have the ability to help create harmony in the Sacramento River — but we can only do it by investing in collaborative science and applying our shared discoveries to inform fish and water management actions and habitat restoration efforts.”

This study sought to identify which runs of Chinook Salmon use the Sutter Bypass, inform our understanding of how water flows through the floodplain, and examine how that water flow impacts the Chinook Salmon life cycle.

“The Sutter Bypass is a critical part of California’s flood management infrastructure,” said Joel Ledesma, Deputy Director of the State Water Project for Department of Water Resources. “DWR’s own work in the downstream Yolo Bypass demonstrates that these floodways can also be successfully managed as fish habitat.”

The research revealed all four runs of Chinook Salmon (fall-, late-fall-, winter- and spring- runs) have the opportunity to move through the Sutter Bypass, and the floodplain system is more complex and dynamic than we thought possible, said Carson Jeffres of the UC Davis Center for Watershed Sciences, who co-led the research. The research also showed that depending on high and low flow conditions, different parts of the Sutter Bypass provided successful rearing habitats for juvenile salmon.

“Conditions are not always perfect” for fish growth, said Flora Cordoleani of the UC Santa Cruz Southwest Fisheries Science Center (SFSC), who co-led the research with Jeffres. “They can be perfect one day — and not the next.”

Scientists expected the Sutter Bypass to behave much like the Yolo Bypass and were surprised by its unpredictable nature. Their findings were the result of an iterative process that required significant trial and error, demonstrating there are big gaps in data and knowledge about how the Sutter Bypass works.

“We really have to think like a fish to understand this dynamic system,” Jeffres said, noting the team plans to continue its research to better understand how floodplains like the Yolo and Sutter bypasses interact, and what implications that has for the fish that live there.

Each year, the SWC is investing more than $2 million in research to increase the scientific community’s understanding of the Delta and its tributaries and species to address some of the state’s water supply challenges.

“We all have a stake in the health of our watersheds,” Pierre said. “As part of the scientific community, our organization is committed to advancing groundbreaking research like this, which is critical to helping us find solutions that truly help to restore habitats and promote a sustainable water supply.”


The State Water Contractors is a statewide, non-profit association of 27 public agencies from Northern, Central and Southern California that purchase water under contract from the California State Water Project. Collectively the State Water Contractors deliver water to more than 27 million residents throughout the state and more than 750,000 acres of agricultural land.