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Fish Passage Improvement Program (FPIP)

Yolo Bypass

photo of river


Inundation of the Yolo Bypass creates habitat for downstream migrating juvenile Chinook salmon (Oncorhynchus tshawytscha), which take advantage of rearing areas created by seasonally inundated vegetation and an enriched food web in the floodplain. Studies show that significantly larger wild Chinook salmon are captured at the downstream end of the Yolo Bypass than at the upstream end, and juvenile salmon in the Yolo Bypass floodplain grow substantially faster than the adjacent Sacramento River, illustrating the importance of this habitat.

The Yolo Bypass is also an adult anadromous fish migration corridor when inundated. Structures within the Yolo Bypass have been a documented source of migratory delay to, and loss of, special status species, including adult Chinook salmon, steelhead (Oncorhynchus mykiss), and green sturgeon (Acipenser medirostris). Improved fish passage at Yolo Bypass barriers (e.g., Fremont Weir) is necessary to improve upstream migration and to reduce associated impacts.


National Oceanic and Atmospheric Administration (NOAA) Fisheries recognized the importance of floodplain rearing habitat and fish passage in the Yolo Bypass in the Biological and Conference Opinion for the Central Valley Project and State Water Project (BO), released on June 4, 2009. Action I.6.1 requires the U.S. Bureau of Reclamation (Reclamation) and California Department of Water Resources (DWR) to "restore floodplain rearing habitat for juvenile winter-run and spring-run Chinook salmon, and Central Valley steelhead (Oncorhynchus mykiss), in the lower Sacramento River Basin. This objective may be achieved at the Yolo Bypass, and/or through actions in other suitable areas of the lower Sacramento River." Action I.7 requires Reclamation and DWR to "reduce migratory delays and loss of salmon, steelhead, and sturgeon, through the modification of Fremont Weir and other structures of the Bypass."

FPIP staff are working with DWR's Division of Environmental Services and Reclamation to implement the Yolo Bypass Salmonid Habitat Restoration and Fish Passage project. The need for the project is to remain in compliance with the Endangered Species Act, by complying with Actions 1.61 and 1.7, as described in the NOAA Fisheries BO and the 2012 Yolo Bypass Salmonid Habitat Restoration and Fish Passage Implementation Plan (PDF, 2.6 MB), prepared by Reclamation and DWR. Both physical and operational modifications will be included in efforts to increase seasonal inundation and improve fish passage.

Pursuant to the California Environmental Quality Act, a Notice of Preparation (PDF, 1.7 MB) of an Environmental Impact Statement/Environmental Impact Report (EIS/EIR) on the Yolo Bypass Salmonid Habitat Restoration and Fish Passage project was circulated for an extended public comment period, beginning March 4, 2013 and ending on May 6, 2013.

Two public scoping meetings were held on March 14, 2013 to inform interested parties about the proposed project and to solicit agency and public input on the scope and content of the EIS/EIR.

Scoping Meeting Materials:

The public comment period for the Notice of Preparation is closed. The Scoping Report (140 K), is now available.

For additional information about the project, please refer to Reclamation's Yolo Bypass Salmonid Habitat Restoration and Fish Passage web page.