California Department of Water Resources (DWR) | September 21st, 2012
Summary
Significant modifications have been made to the historic floodplain of California‘s Central Valley for water supply and flood damage reduction purposes. The resulting l
Significant modifications have been made to the historic floodplain of California‘s Central Valley for water supply and flood damage reduction purposes. The resulting losses of rearing habitat, migration corridors, and food web production for fish have significantly hindered native fish species that rely on floodplain habitat during part or all of their life history.
The Yolo Bypass (Bypass), which currently experiences at least some flooding in approximately 80% of years, still retains many characteristics of the historic floodplain habitat that are favorable to various fish species. In approximately 70% of years, Fremont Weir overtops, joining flows from western tributaries. In approximately 10% of years, localized flooding is due to western tributary contributions only (DWR 2008, Woodland gauge, unpublished analysis).
The primary function of the Bypass is flood damage reduction, with most of it also managed as agricultural land. The Bypass has also been identified by several State and federal entities as a potential site for habitat restoration to ease pressure on and increase benefits to threatened and endangered fish species.
On June 4, 2009, the National Marine Fisheries Service (NMFS) issued its Biological Opinion and Conference Opinion on the Long-term Operation of the Central Valley Project (CVP) and State Water Project (SWP) (NMFS Operation BO). The NMFS Operation BO concluded that, if left unchanged, CVP and SWP operations were likely to jeopardize the continued existence of four federally- listed anadromous fish species: Sacramento River winter-run Chinook salmon, Central Valley spring-run Chinook salmon, California Central Valley steelhead, and Southern Distinct Population Segment (DPS) North American green sturgeon. The NMFS Operation BO sets forth Reasonable and Prudent Alternative (RPA) actions that would allow continuing SWP and CVP operations to remain in compliance with the federal Endangered Species Act (ESA).
This Yolo Bypass Salmonid Habitat Restoration and Fish Passage Draft Implementation Plan (Implementation Plan) was prepared jointly by the California Department of Water Resources (DWR) and the U.S. Bureau of Reclamation (Reclamation) to address two specific RPA Actions set forth in the NMFS Operation BO: RPA Action I.6.1: Restoration of Floodplain Rearing Habitat, through the increase of seasonal inundation within the lower Sacramento River basin; and RPA Action I.7: Reduce Migratory Delays and Loss of Salmon, Steelhead, and Sturgeon, through the modification of Fremont Weir and other structures of the Yolo Bypass.
As mandated by the NMFS Operation BO, this Implementation Plan describes the activities, process, and timeline required to implement actions to address the requirements of RPA Actions I.6.1 and I.7.
Major California restoration planning efforts over several decades (e.g., CALFED, the Bay Delta Conservation Plan) have focused on the Yolo Bypass as a prime area of the Sacramento Valley for enhancement of seasonal floodplain rearing habitat. The Yolo Bypass is generally seen as one of the best places in the lower Sacramento River Basin on which to focus implementation resources in order to achieve implementation of floodplain enhancements because of these efforts. Some of the technical foundation for these efforts has been well laid and interaction with stakeholders and local property owners has been initiated and is on-going.
Implementation procedures related to RPA Action I.6.1 within the NMFS Operation BO specify that this Implementation Plan include an evaluation of options to "increase aquatic inundation of publicly and privately owned suitable acreage within the Yolo Bypass." Therefore, this Implementation Plan focuses on restoration of floodplain rearing habitat within the Yolo Bypass to address RPA Action I.6.1. However, the planning and environmental compliance process will consider a reasonable range of alternatives for implementing this RPA action. Additional discussion regarding the availability and suitability of areas for seasonal floodplain inundation is provided in Section 6: Proposals to Refine the RPA Actions.