Sacramento River

Salinity of deep groundwater in California: Water quantity, quality, and protection

National Academy of Sciences (NAS) | July 12th, 2016

Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and g

Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and gas extraction, and this activity has created both valuable data and risks to groundwater quality. Assessing groundwater quantity and quality requires baseline data and a monitoring framework for evaluating impacts. We analyze 938 chemical, geological, and depth data points from 360 oil/gas fields across eight counties in California and depth data from 34,392 oil and gas wells. By expanding previous groundwater volume estimates from depths of 305 m to 3,000 m in California’s Central Valley, an important agricultural region with growing groundwater demands, fresh [<3,000 ppm total dissolved solids (TDS)] groundwater volume is almost tripled to 2,700 km3, most of it found shallower than 1,000 m. The 3,000-m depth zone also provides 3,900 km3 of fresh and saline water, not previously estimated, that can be categorized as underground sources of drinking water (USDWs; <10,000 ppm TDS). Up to 19% and 35% of oil/gas activities have occurred directly in freshwater zones and USDWs, respectively, in the eight counties. Deeper activities, such as wastewater injection, may also pose a potential threat to groundwater, especially USDWs. Our findings indicate that California’s Central Valley alone has close to three times the volume of fresh groundwater and four times the volume of USDWs than previous estimates suggest. Therefore, efforts to monitor and protect deeper, saline groundwater resources are needed in California and beyond.

Salt Water Problem: San Francisco Bay and Delta of Sacramento and San Joaquin Rivers

Association of Industrial Water Users of Contra Costa and Solano Counties | April 12th, 1928

PENETRATION OF SALT WATER IN UPPER BAY AND LOWER RIVER REGiON Under natural conditions, Carquinez Straits marked, approximately, the boundary between salt and fresh

PENETRATION OF SALT WATER IN UPPER BAY AND LOWER RIVER REGiON Under natural conditions, Carquinez Straits marked, approximately, the boundary between salt and fresh water in the upper San Francisco Bay and delta region of the two tributary rivers-the Sacramento and San Joaquin. Ordinarily salt water was present below the straits and fresh water was present above. Native vegetation in the tide marshes was predominantly of salt water types around San Pablo Bay and of fresh water types around Suisun Bay. In tidal waters, into which run fresh water streams of variable flow, there is an ebb and flow of salt water and the zone of mixing will move up and down stream as the fresh water flow increases and decreases. For short intervals in late summer of years of minimum flow, salt water penetrated the lower river and delta region, and in wet seasons the upper bay was fresh, part of the time, to the Golden Gate. This variation in quality of water was not, however, of sufficient duration to affect the characteristic vegetation growth of the regions on each side of the straits, nor to change the designation of Suisun Bay as ordinarily a fresh water body and San Francisco Bay as salt water. The works of man have changed conditions in many ways. The most important changes have been brought about gradualJy,-so slowly as to be hardly noticeable. The dry season of 1918,-when large summer diversions for irrigation in the Sacramento Valley resulted in the sudden penetration of salt water farther upstream than ever known before, at such an early period in summer first brought the salt water problem to public notice. The slow effects of increasing diversions in previous years had escaped notice, but were brought prominently to the attention of the inhabitants of the upper bay and delta regions in this year. Since 1918, the dry years of 1920, 1924- and 1926 have more convincingly demonstrated the importance of the salt water problem. An accurate picture of natural conditions is not possible, because no records have been collected on which such a picture can be based, but very close approximations can be made. The log of the distance traveled by the water barge of the California Hawaiian Sugar Company in going upstream to obtain fresh water has been kept since 1908. These figures give the means of determining approximately the conditions during that period. In 1908 irrigation had been extensively developed in both valleys and conditions then were not natural. For an estimate of earlier conditions we must go to the stream flow records of the tributary streams before important diversions are taken out. It is the practice of the Sugar Company to send the barge upstream until water of approximately 50 to 70 parts per million chlorine is reached. The crew of the barge are equipped with apparatus by which water is analyzed until this degree of purity is reached. Since trips are made nearly every day during the summer months, the record is a very good indication of the point reached by salt water. A summary of the complete records shows the fluctuation of the line between fresh and salt water. Records of the Sugar Company arc attached. (Table 1.) The Sugar Company requires water of great purity. For irrigation, domestic or ordinary industrial uses, water of a lesser degree of purity may be used. A comparison of the point where the Sugar Company's barge is filled with the point where the remaining uses could be satisfied, indicates that from five to ten miles downstream from the place where the barge turns, water could be obtained satisfactory for domestic supply. Making an allowance of 7 1/2 miles in the average records, we find that an average flow of 5,000 second feet in both streams will maintain fresh water at Collinsville; 7,000 second feet will maintain fresh water at the San Francisco-Sacramento ferry. If we sum up the flow of the important tributaries of the Sacramento and San Joaquin rivers at the points where these streams leave the mountains and assume that this flow under natural conditions would have reached the head of the Suisun Bay we will find that at no time in the past ten years would the average monthly flow have been Jess than 5,100 second feet. It is probable, should all streams be running in a natural way, that salt water would have penetrated no farther in this extremely dry period than Antioch, and then only for a few days at a time. It is not possible to make a more detailed study of this condition without making a number of assumptions as to speed of flow from the gaging stations to the head of the bay, and there is little accurate information on which the assumptions may be made. The definite statement that salt water under natural conditions did not penetrate higher upstream than the mouth of the river, except in the driest years and then only for a few days at a time, is warranted. (See Table 2 for monthly flow of tributary streams.) At present salt water reaches Antioch every year, in two-thirds of the years running further upstream. It is to be expected that it will continue to do so in future, even in years of greatest runoff. In other words, the penetration of salt water has become a permanent phenomenon in the lower river region.

Sampling for Per- and Polyfluoroalkyl Substances (PFAS) by the Groundwater Ambient Monitoring and Assessment Priority Basin Project

Publisher not available | May 25th, 2021

San Francisco Bay California Toxics Rule Priority Pollutant Ambient Water Monitoring Report

San Francisco Estuary Institute (SFEI) | February 1st, 2017

In 2000, the USEPA published Water Quality Standards; Establishment of Numeric Objectives for Priority Toxic Pollutants for the State of California, commonly known as t

In 2000, the USEPA published Water Quality Standards; Establishment of Numeric Objectives for Priority Toxic Pollutants for the State of California, commonly known as the California Toxics Rule (CTR), which established numeric water quality standards for 126 priority pollutants. Under the Policy for Implementation of Toxics Standards for Inland Surface Waters, Enclosed Bays, and Estuaries of California (also known as the State Implementation Policy, SIP) the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB) is required to establish water quality-based effluent limitations in order to achieve priority pollutant standards. For the purposes of this document “water quality criteria” (WQCs) will be used to refer both to the CTR established numeric criteria for 126 priority pollutants as well as to numeric objectives for 12 of these priority pollutants and tributyltin previously established in the San Francisco Bay Water Quality Control Plan (Basin Plan) and/or the National Toxics Rule. A number of these pollutants previously were or continue to be regularly monitored as part of the Regional Monitoring Program Status and Trends (RMP S&T). The priority pollutants not routinely included in RMP S&T were previously monitored in wet and dry season ambient water sampling in 2002 and 2003. Results of that effort are detailed in a previously issued : Most of the priority pollutants were not detected in that study, or detected at concentrations below their WQC. Among the pollutants that were detected, a number of them were also found at similar concentrations in lab blanks, suggesting they might not have been present (or at least were at lower concentrations) in the ambient environment. Since over a decade had passed since that previous monitoring effort, the RMP embarked on an effort to repeat measurement of these seldom analyzed (non- S&T) contaminants, to ensure conditions have not changed appreciably to present greater risk for any of them.

San Francisco Bay: A Freshwater Starved Estuary

Bay Institute | September 1st, 2016

How Reducing Flows Harms the Ecosystems of San Francisco Bay and Coastal Waters The Bay Institute’s major new study, San Francisco Bay: The Freshwater – Starved Estu

How Reducing Flows Harms the Ecosystems of San Francisco Bay and Coastal Waters The Bay Institute’s major new study, San Francisco Bay: The Freshwater – Starved Estuary, documents how the ecological health of San Francisco Bay and the nearby ocean is at high risk because large-scale water diversion in the Bay’s watershed severely limits the amount of fresh water that reaches the Bay and alters the timing of that flow. Inflow to the Bay from its Central Valley watershed now averages less than half of what it would be without diversions; in some years just one-third of the runoff makes it to the Bay. The result is a nearly permanent drought for the Bay’s fish, wildlife, and their habitats. This radical alteration creates severe consequences for the Bay and marine ecosystems – and Bay Area residents pay the price. The study shows how unsustainable diversion of the Bay’s freshwater inflow: Dramatically cuts production of fish and shrimp that are the food source for marine mammals, like Orca Whales, and birds; Allows pollutants to accumulate to dangerous levels and encourages blooms of toxic algae; Reduces sediment supply to Bay Area wetlands and beaches; Makes it easier for undesirable non-native species to successfully invade the Bay Estuary. The San Francisco Bay Estuary is created by the mixing of fresh water from the Central Valley’s rivers with salt water from the Pacific Ocean. Dramatically reducing the inflow of fresh water generates cascading effects in the Bay’s watershed, the Bay itself, and coastal ocean waters. The report’s major findings include: On average, since 1975 more than half (53%) of runoff from the Central Valley watershed has been diverted, stored, or exported before it can reach the Bay – and in many years two-thirds or more of the Bay’s inflow is captured; As a result of intensive water diversions, the Bay experiences catastrophically dry years almost half the time (only one “supercritically dry” year occurred naturally between 1975-2014, but the Bay experienced nineteen supercritical years during that period); Numerous unrelated fish species – from sharks to salmon, from sturgeon to smelt – show strong positive correlations with Bay Inflow; many of these species are now endangered, and even commercially viable fisheries are in decline; Predators that feed on flow-dependent fish and shrimp are feeling the pinch – for example, dwindling supplies of Central Valley Chinook salmon may restrict the recovery of the local Orca whale population; Blooms of toxic “algae” (cyanobacteria) are becoming more frequent, and other pollutants are becoming more concentrated, as a result of reductions in freshwater flows from the Bay’s watershed; Bay Area beaches and tidal wetlands are deprived of sediment that was once transported by high river flows. The study reports that local businesses are likely to suffer from the Bay’s continued decline, including those related to commercial fishing and tourism. As our Bay, beaches, wetlands, and fish and wildlife populations deteriorate, the quality of life for many Bay Area residents will also be severely – and perhaps permanently – damaged. The study identifies four important approaches to improving Bay inflows: Update the State’s 21 year old water quality standards for the Bay Estuary to ensure adequate inflow Require all those who divert water destined for the Bay, not just a subset, to contribute their fair share of fresh water to support benefits enjoyed by all Californians Invest in local water supplies around the state including conservation, and recycling, that can generate millions of acre-feet of water and reduce reliance on water diverted from the Estuary and its watershed Coordinate management of flows with wetland and beach restoration to more effectively protect shorelines The study was prepared for the San Francisco Estuary Partnership, a coalition of resource agencies, non-profits, citizens, and scientists working to protect, restore, and enhance water quality and fish and wildlife habitat in and around the San Francisco Bay Delta Estuary, which also provided the majority of funding for the project.

San Francisco Estuary Blueprint 2022

San Francisco Estuary Partnership (SFEP) | September 8th, 2022

In the past few years, the San Francisco Estuary region has confronted epic wildfires, historic rainfall intensity and flooding, and chronic drought. The whiplash of thes

In the past few years, the San Francisco Estuary region has confronted epic wildfires, historic rainfall intensity and flooding, and chronic drought. The whiplash of these events has confirmed that climate change has already begun to impact human and wildlife communities from Sacramento to San Francisco, and beyond. Furthermore, a global COVID-19 pandemic has disrupted regional planning and project implementation everywhere, presenting new challenges to traditional processes and creating an unfamiliar working landscape for resource managers. Finally, the pervasive, horrific violence against Black, Brown, and Asian and Asian-American people has amplified long-term calls for racial justice, galvanizing new commitments to address historic and present inequity through every thread of our social fabric. These events have set the context for the multi-stakeholder process that updates the San Francisco Estuary Blueprint.

San Francisco Estuary Blueprint 2022 (Comprehensive Conservation and Management Plan for the San Francisco Estuary)

San Francisco Estuary Partnership (SFEP) | March 16th, 2022

Click here for the definition of a Comprehensive Conservation and Management Plan)

Click here for the definition of a Comprehensive Conservation and Management Plan)

San Joaquin Valley Conveyance Study

California Department of Water Resources (DWR) | November 24th, 2025

This San Joaquin Valley Conveyance Study analyzes water conveyance needs in the San Joaquin Valley (Figure ES-1). The purpose of this study is to: •Describe the impa

This San Joaquin Valley Conveyance Study analyzes water conveyance needs in the San Joaquin Valley (Figure ES-1). The purpose of this study is to: •Describe the impacts of subsidence on San Joaquin Valley conveyance facilities. •Evaluate the need for improved or expanded conveyance facilities throughout the San Joaquin Valley.  

Sand Supply to San Francisco Bay from the Sacramento and San Joaquin Rivers of the Central Valley, California

U.S. Geological Survey (USGS) | October 30th, 2024

Sediment from the Central Valley via the Sacramento-San Joaquin Delta (Delta) and Suisun Bay is a primary source of sand to San Francisco Bay, California. Sand is mined f

Sediment from the Central Valley via the Sacramento-San Joaquin Delta (Delta) and Suisun Bay is a primary source of sand to San Francisco Bay, California. Sand is mined from San Francisco Bay for commercial purposes, such as for use in concrete for construction. To better understand the supply of sand to Suisun Bay and San Francisco Bay, the U.S. Geological Survey (USGS), in cooperation with the San Francisco Bay Estuary Institute (SFEI) and the San Francisco Bay Conservation Development Commission (BCDC), initiated this study to compile and synthesize historical data and estimate the total sediment and sand portion of sediment exiting the Delta to Suisun Bay for a 20-year period between water years 2001 and 2020.

SB-72 The California Water Plan: long-term supply targets

State of California | September 8th, 2025

Existing law requires the Department of Water Resources to update every 5 years the plan for the orderly and coordinated control, protection, conservation, development, a

Existing law requires the Department of Water Resources to update every 5 years the plan for the orderly and coordinated control, protection, conservation, development, and use of the water resources of the state, which is known as “The California Water Plan.” Existing law requires the department to include a discussion of various strategies in the plan update, including, but not limited to, strategies relating to the development of new water storage facilities, water conservation, water recycling, desalination, conjunctive use, and water transfers, that may be pursued in order to meet the future needs of the state. Existing law requires the department to establish an advisory committee to assist the department in updating the plan. This bill would revise and recast certain provisions regarding The California Water Plan to, among other things, require the department to expand the membership of the advisory committee to include, among others, tribes, labor, and environmental justice interests. The bill would require the department, as part of the 2033 update to the plan, to update the interim planning target for 2050, as provided. The bill would require the target to consider the identified and future water needs for all beneficial uses, including, but not limited to, urban uses, agricultural uses, tribal uses, and the environment, and ensure safe drinking water for all Californians, among other things. The bill would require the plan to include specified components, including a discussion of the estimated costs, benefits, and impacts of any project type or action that is recommended by the department within the plan that could help achieve the water supply targets. The bill would require the department to report to the Legislature the amendments, supplements, and additions included in the updates of the plan, together with a summary of the department’s conclusions and recommendations, in the session in which the updated plan is issued. The bill would also require the department to conduct public workshops to give interested parties an opportunity to comment on the plan.