Riverine Habitat Restoration Projects

DWR and U.S Bureau of Reclamation (Reclamation) developed the Yolo Bypass Salmonid Habitat Restoration and Fish Passage (Big Notch) Project to improve fish passage and increase fish rearing habitat on the floodplain of the Yolo Bypass and the lower Sacramento River basin. Completed in 2025, the project primarily consists of a Fremont Weir headworks structure, an outlet channel, and downstream channel improvements.

To improve fish passage, two associated future projects will also be constructed - Agricultural Road Crossing 1 and the Supplemental Facility (more details below in the "Future Projects" section). 

Planning and Design: The Final Environmental Impact Statement/Environmental Impact Report (EIS/EIR) was released on June 7, 2019. An electronic copy of the Final EIS/EIR can be accessed on Reclamation’s website. The Notice of Determination (NOD) was signed and filed with the State Clearinghouse on July 19, 2019 and can be accessed via CEQAnet (State Clearinghouse Number 2013032004).

Operations: The goal of Big Notch operations is to maximize the number of juvenile Chinook salmon migrating into the Yolo Bypass and provide adequate adult fish passage for sturgeons and salmonids to the Sacramento River.

Big Notch is authorized to provide flow through the headworks to enhance juvenile rearing habitat and provide juvenile and adult fish passage. However, flows through the headworks after March 15 cannot exceed the available capacity of Tule Canal, around 1,000 cfs of flow. Tule Canal capacity is approximate and depends on flows from BNP as well as tailwater conditions from agriculture drainage, tides, and west-side tributary inflows, primarily Cache Creek and Knights Landing Ridge Cut.

Monitoring: The Adaptive Management and Monitoring Plan includes monitoring for certain key performance measures. The Adaptive Management and Monitoring Plan as well as the associated study plans and annual monitoring reports are available upon request.

DWR and Reclamation constructed the Fremont Weir Adult Fish Passage Facility in 2019 to improve salmonid and sturgeon passage in the Yolo Bypass by:

• Modifying the existing Fremont Weir fish ladder to provide upstream passage when the Sacramento River overtops Fremont Weir and immediately after the river recedes.

• Improving fish passage conditions in the channel that extends from the existing fish ladder upstream to the Sacramento River and downstream to the existing deep pond.

• Further downstream in Tule Canal, removing one earthen agricultural road crossing and replacing another earthen agricultural road crossing with a structure that allows for fish passage through the Tule Canal and continued agricultural utility.

Planning and Design Status: In 2017, DWR and Reclamation released an Initial Study and Environmental Assessment and Mitigated Negative Declaration for the Fremont Weir Adult Fish Passage Modification Project for public review. An electronic copy can be accessed on Reclamation's Website. A Notice of Determination (NOD) was filed with the State Clearinghouse in August of 2017 (State Clearinghouse Number 2017022012). 

Operations: The gated structure is opened during Fremont Weir overtopping events when the Sacramento River reaches a stage of 32.3 feet at the facility. In accordance with the Notice of Determination, DWR operates AFP under the following two operation scenarios:

Scenario 1: The fish passage structure remains open for three days after Fremont Weir stops overtopping; or

Scenario 2: The fish passage structure remains open for one day after Fremont Weir stops overtopping and reopens when the river stage falls below 27 feet and closes when the river stage reaches 24 feet, for no longer than five days.

Wallace Weir is a water control structure on the Knights Landing Ridge Cut Slough where the canal flows into the west side of the Yolo Bypass. Historically, adult salmon became stranded in agricultural ditches of the Colusa Basin Drain System, especially when flows in the Knights Landing Ridge Cut Slough were elevated. With no upstream route to return to the Sacramento River, these fish would perish without spawning. 

DWR replaced the historic earthen dam, which would wash away during high flow events, with a permanent structure in 2019 that prevents migration of salmon and sturgeon into the Knights Landing Ridge Cut Slough and dead-end Colusa Basin Drain. The project also includes a fish collection facility to allow for efficient trapping and relocation of adult salmonids and sturgeons to the Sacramento River to continue their spawning migration. Visit our Wallace Weir Story Map for more details on the development and history of this fish rescue facility.

Planning and Design: DWR worked with Reclamation District (RD) 108 to plan and permit this project. The Initial Study and Mitigated Negative Declaration was released in April 2016. Please visit Reclamation District 108's website for additional information on the planning and design of the Wallace Weir Fish Rescue Facility. 

Operations and Monitoring:  The Wallace Weir Fish Rescue Facility is comprised of a Water Control Structure (WSC) and Fish Collection Facility (FCF). The WCS uses a combination of gates and picket weirs to control flood flows from the Colusa Basin Drain and block the upstream migration of adult fish. The FCF is operated to capture and relocate these fish to the Sacramento River. Operation of the WCS is dependent on conditions at the upstream Knights Landing Outfall Gates. The FCF portion of Wallace Weir will be operated to capture and relocate adult migratory fish when they are likely to be present in the project area (typically between September 1 and June 30). Fish monitoring data from the Wallace Weir Fish Rescue Facility can be found on the CalFish website.

The Yolo Bypass Salmonid Habitat Restoration and Fish Passage Implementation Plan identified Agricultural Road Crossing 4 as a fish passage impediment. To meet requirements of the Endangered Species Act, DWR and Reclamation plan to share the cost of this fish passage improvement project.

The current facility is an earthen road crossing with operable culverts that spans Tule Canal, just south of where the Sacramento Bypass connects with the Yolo Bypass. The crossing also provides the ability to impound water for agricultural and waterfowl purposes. This project will replace the existing earthen agricultural crossing with a permanent bridge structure that spans the Tule Canal and provide unimpeded fish passage. The water impoundment component of the facility will be addressed through a separate non-DWR project. 

Planning and Design Status: In conjunction with CDFW and Reclamation, DWR sent a Notice of Exemption under CEQA for the Agricultural Road Crossing #4 bridge project to the State Clearinghouse in July 2021 (Clearinghouse Number 2021070310). A Notice of Determination (NOD) and final Initial Study and Mitigated Negative Declaration (IS/MND) and Environmental Assessment (EA) for the pump infrastructure relocation were approved in October 2023 and posted to the State Clearinghouse in December 2023 (State Clearinghouse Number 2023090717). All permits were received by October 2024.

Construction: Construction is in progress and started in 2024.

To improve fish passage, the Big Notch Project included development of two associated projects, Agricultural Road Crossing 1 (ARC1) and the Supplemental Fish Passage Facility (SFP). The ARC1 project removes an earthen road crossing that spans Tule Canal, just south of Tule Pond in the Yolo Bypass. The SFP project will construct a manual fish gate in the Fremont Weir so that adult fish caught in the west portion of the Fremont Weir stilling basin can be relocated into the Sacramento River. Currently no gate or ladder is available at this location to move adult fish into the Sacamento River.

Planning and Design Status: Preliminary design for the project has been completed and permits are in the process of being submitted to the appropriate regulatory agencies.

Anticipated Construction: 2025