Water Quality Conditions in the Sacramento-San Joaquin Delta during 1995

California Department of Water Resources (DWR) | August 1st, 1999

Water year 1995 was a wet year, ending an eight-year period of predominantly dry and critically dry years.  After a relatively dry fall, January and March precipitation

Water year 1995 was a wet year, ending an eight-year period of predominantly dry and critically dry years.  After a relatively dry fall, January and March precipitation was heavy and produced flooding in the Central Valley.  By May 1, precipitation was 165% of average, snowpack water content was 215% af average, seasonal runoff was 170% of average, and reservoir storage was 110% of average. In 1995, the Net Delta Outflow Index (NDOI) was used to estimate Delta outflow, and the Sacramento and San Joaquin River Unimpaired Runoff indices were used to determine water year type for 1995.  Using these indices, water year 1995 was officially classified as wet on May 1, 1995.  All standards, including those in Water Right Decision 1485, as amended by the 1995 Water Quality Control Plan, were met in 1995. The entire 1995 calendar year was characterized by excess conditions, and both State Water Project and Central Valley Project water requirements were met as well as in-Delta consumptive uses.  Delta outflows were high throughout the year, and the calculated average monthly flows exceeded 80,000 cubic feet per second (CFS) during the peak outflow period (January through May), and 3,000 cfs during the minimum outflow period (July through November).

Water Quality in the State Water Project, 2000 and 2001

California Department of Water Resources (DWR) | April 1st, 2004

Water quality is routinely monitored at about 30 stations throughout the State Water Project (SWP). Water quality samples are collected by staff of the five field divisio

Water quality is routinely monitored at about 30 stations throughout the State Water Project (SWP). Water quality samples are collected by staff of the five field divisions in the Division of Operations and Maintenance and sent to Bryte Laboratory for analysis. SWP stations include those located in the Feather River watershed, North Bay Aqueduct, South Bay Aqueduct, and the California Aqueduct with its four terminus lakes in Southern California (Figure 1-1). Samples are collected on the third Wednesday of each month at the regular stations. Analyses include minerals, metals, metalloids, nutrients, organic chemicals, and disinfection by-product precursors. Further, around 15 automated water quality stations continuously monitor parameters such as salinity and turbidity on a real-time basis. Station descriptions and water quality constituents analyzed are detailed in Appendix A. Monitoring in the SWP is done on a routine basis to identify trends and assess water quality conditions with respect to long-term trends, operations, hydrology, seasons, emergencies, water treatment issues, and drinking water standards. Primary and secondary Maximum Contaminant Levels (MCLs) apply to drinking water and were compared to SWP data to provide a relative indication of raw water quality. MCLs are presented in Appendix B. Water quality trend assessment focused on salinity, bromide, and organic carbon. Water quality in the California and South Bay Aqueducts was good during 2000 due, in part, to above normal water year conditions in the Sacramento and San Joaquin Valleys. Drier conditions in 2001 resulted in less favorable water quality with respect to mineralogy. North Bay Aqueduct exports exhibited the usual impairments during winter as a result of organic carbon and turbidity increases. Water quality in the Feather River watershed was excellent, as usual, with low to non-detectable levels of minerals and minor elements.

Water Right Decision 1485: Sacramento-San Joaquin Delta and Suisun Marsh

California State Water Resources Control Board (SWRCB) | August 16th, 1978

Water Surplus and Drought Management Update - Conditions as of 11/29/2022

Metropolitan Water District of Southern California (MWD) | December 13th, 2022

Water Year 2018 Hydrology

Delta Stewardship Council (Delta Council) | November 26th, 2018

West False River Drought Salinity Barrier Final EIR

California Department of Water Resources (DWR) | November 8th, 2024

With the proposed project, a temporary drought salinity barrier would be installed in West False River up to two times over 10 years, with each installation remaining in

With the proposed project, a temporary drought salinity barrier would be installed in West False River up to two times over 10 years, with each installation remaining in place for up to 20 months over two consecutive calendar years. The barrier would be installed if a drought were to occur during the 2026–2035 period and the drought conditions indicate that a barrier in West False River would be an effective tool to preserve upstream reservoir storage for health, safety, and regulatory releases, while preventing saltwater intrusion into the central and southern portions of the Sacramento–San Joaquin Delta (Delta). The drought salinity barrier would be constructed only if DWR, in cooperation with other State and federal agencies, determines that drought conditions have reduced water storage in Northern California reservoirs to critical levels, such that projected Delta outflow would be insufficient to control increased salinity intrusion into the Delta. 

Yolo Bypass Salmon Habitat Restoration and Fish Passage Analytical Tool Review

Delta Stewardship Council (Delta Council) | October 1st, 2017

NOAA’s National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) have issued a Biological Opinion (BiOp) on the long-term operat

NOAA’s National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) have issued a Biological Opinion (BiOp) on the long-term operations of the Central Valley Project (CVP) and State Water Project (SWP) that includes Reasonable and Prudent Alternatives (RPA) designed to alleviate jeopardy to listed species and adverse modification of critical habitat. NMFS’ RPA requires the U.S. Bureau of Reclamation (Reclamation) to increase juvenile flood plain rearing habitat and improve adult fish passage for ESA-listed salmonids and sturgeon. The BiOp requires seventy-three (73) habitat restoration actions, five of which are specific to the Yolo Bypass. The California Department of Water Resources (DWR) and Reclamation have developed project alternatives for the Draft Yolo Bypass Fish Passage and Habitat Restoration EIS/EIR focused on the following two Yolo Bypass actions, which are the subject of this review:  - Increase seasonal floodplain inundation in the lower Sacramento River Basin  - Improve fish passage throughout the Yolo Bypass Alternatives The alternatives developed to address these two actions consist of a notch in the Fremont Weir, with alternative locations and configurations (width and weir-crest elevations), designed to increase the frequency and duration of hydraulic connectivity between the main-stem Sacramento River and the Yolo Bypass and to improve fish passage. Six alternative locations / configurations for a notch were identified.

Yolo Bypass Salmonid Habitat Restoration and Fish Passage Implementation Plan

California Department of Water Resources (DWR) | September 21st, 2012

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.

Yuba-Feather FIRO Final Viability Assessment

California Department of Water Resources (DWR) | March 14th, 2025

This Yuba-Feather Final Viability Assessment (FVA) evaluates whether improved precipitation and runoff forecasts can reduce flood risk downstream of New Bullards Bar (NBB

This Yuba-Feather Final Viability Assessment (FVA) evaluates whether improved precipitation and runoff forecasts can reduce flood risk downstream of New Bullards Bar (NBB), owned and operated by Yuba Water Agency (Yuba Water), and Lake Oroville (ORO), owned and operated by the California Department of Water Resources (DWR). These reservoirs are in the Yuba-Feather watersheds in the Sierra Nevada and eastern Sacramento Valley of Northern California (Figure ES-1 and ES-2). Each reservoirs’ flood risk reduction operations are regulated by United States Army Corps of Engineers (USACE) through Water Control Manuals (WCMs).  Reducing flood risk by making reservoir releases ahead of storms creates additional temporary flood storage space for anticipated inflows but requires confidence and skill in forecasted conditions.