Variability and extremes in weather, hydrology and other forces is characteristic for the Sacramento-San Joaquin Delta. Detecting the effects of management actions within these larger external changes can be difficult if you are not routinely looking for it. This web page summarizes the significant changes observed by the scientists who measured the effectiveness of management actions in the Delta throughout 2024.
Introduction
Using data to track the health of California’s Delta is critical to achieving a reliable statewide water supply and a resilient ecosystem that protects and enhances the Delta as a place where people live, work, and recreate. Environmental managers and scientists who work in the Delta must be informed about the Delta Plan’s performance measure changes annually to:
- Ensure that environmental decision-making is based on the best available science and
- Evaluate the overall effectiveness of Delta Plan implementation.
Changes over multiple years that indicate significant trends could lead to potential amendments to state policy, the Delta Plan, and on-the-ground management approaches. This web page aims to communicate the yearly progress of performance measures.
The performance measures featured in the collapsible accordion bars below reflect the changing conditions that scientists observed throughout the 2023 water year. More information about each can be found on their respective web pages.
2024 CONDITIONS
In 2024, California experienced normal hydrologic conditions and higher-than-average temperature conditions. The Water Year 2024 was unusually normal, with an average rainfall of 70–130% of normal precipitation amounts. California recorded one of the hottest summers on record, with daily summer temperatures averaging 3–7°F higher than normal.
The performance measures highlighted below describe updates in areas of a reliable water supply, ecosystem restoration, Delta water quality, and subsidence prevention.
Performance Measure Spotlights
Why measure Urban Water Use?
Monitoring improvements in urban water conservation and water use efficiency is critical to understanding local self-reliance and reduced use of Delta water. The Council’s urban water use performance measure tracks gallons of water per capita per day used and the water conservation targets set by individual water suppliers.
What happened in 2024?
In 2024, the State Water Resources Control Board adopted the “Make Conservation a California Way of Life” regulation. The regulation establishes goals for each Urban Retail Water Supplier; based on the unique characteristics of the supplier’s service area and gives suppliers the flexibility to implement local solutions.
Why is this important?
The newly established water conservation goals are expected to reduce urban water use by more than 400,000 acre-feet by 2030, helping California adapt to the water supply impacts brought on by climate change. As the climate becomes hotter and dryer and as California’s population grows, managing water demand through urban conservation will become even more crucial.
What steps are being taken in 2025?
In 2025, the new water conservation regulation is in effect and the first of the required annual reports from required Urban Water Suppliers are due.
For more details, visit the Urban Water Use performance measure.
Why track the Sustainable Groundwater Management Act (SGMA) implementation?
Sustainable Groundwater Management Act (SGMA) addresses chronic groundwater overdrafts throughout California. Understanding how the appropriate agencies carry out their SGMA responsibilities is important to ensure government transparency and accountability.
What happened in 2024?
2024 was the tenth anniversary of SGMA. During the decade, over 250 Groundwater Sustainability Agencies (GSAs) were established, and over 100 Groundwater Sustainability Plans (GSPs) were developed addressing groundwater overdraft and regional water supply reliability. The formation of GSAs and GSPs also resulted in improvements in groundwater data tracking with over 9,000 wells monitored in water year 2024 and increased funding for local groundwater recharge projects.
Why is this important?
Groundwater overdraft occurs in regions that rely upon Delta watershed water. Actions to ensure the long-term sustainability of the groundwater are essential to local self-reliance and improved reliability in regional water supply. Climate change forecasts will make it critical to balance groundwater replenishment and flood water diversions from the Delta watershed with the state’s policy of reducing reliance on Delta water.
What steps are being taken in 2025?
Going forward, the focus will be on implementing the GSPs to achieve sustainable groundwater conditions by 2040. The emphasis is also on projects that can capture flood water and recharge the groundwater supply during wet years.
For more details, visit the Sustainable Groundwater Management performance measure.
Why measure Yolo Bypass Inundation?
Yolo Bypass is a large floodplain habitat adjacent to the lower section of the Sacramento River. The Bypass provides important flood control to adjacent urban areas and supports native fish spawning and rearing when flooded.
What happened in 2024?
In 2024, the Yolo Bypass flooded in the spring for the second year in a row, achieving the desired ecosystem targets for the duration, frequency, and extent of floodplain inundation.
Why is this important?
Frequently flooded Yolo Bypass has the potential to contribute to the growth of native migratory fish species and the Delta food webs by restoring floodplain and wetland ecological functions. Native fish species such as Chinook salmon, steelhead, and Sacramento Splittail have higher growth rates and consequently increased survival rates after they migrate through the Yolo Bypass.
What steps are being taken in 2025?
A large-scale restoration project, the Big Notch project, is being completed and will be opening 30,000 acres of floodplain habitat in the Yolo Bypass for more frequent and longer flooding that is expected to benefit the native fish in the lower Sacramento River and the Delta.
For more details, visit the Yolo Bypass Inundation performance measure.
Why measure Salmon Doubling?
Salmon are native anadromous fish and a strong indicator of ecosystem health. The Delta Plan aligns with the state and federal goal of doubling the natural production of Central Valley salmon long-term. The performance measure tracks the annual average natural production of Chinook salmon in the Central Valley for select rivers of the Sacramento-San Joaquin Delta watershed. Salmon abundances are used as a proxy for natural production due to the higher accessibility of abundance data compared to natural production data.
What happened in 2024?
Over the past decade, salmon runs in Delta tributaries averaged about 12% of the doubling goal. In 2023, the latest data available, salmon natural production tripled the 2022 counts in certain tributaries such as the American River, Feather River, and Mokelumne River. Salmon populations in other tributaries continue to dwindle. Listed populations of spring-run and winter-run salmon are declining.
Why is this important?
The Delta is an important habitat for Central Valley salmon populations as they migrate between upstream tributaries and the Pacific Ocean. Salmon plays an important role in ecosystems. In addition to ecological importance, salmon have sociocultural significance to many Native American communities and are an integral part of California’s fishing industry.
What steps are being taken in 2025?
A statewide Salmon Strategy was released in 2024 aiming to stabilize and recover California salmon populations and restore entire aquatic ecosystems in the face of climate change. Implementation of the strategy aims to remove fish passage barriers, restore habitat, protect water flows, modernize hatcheries, and strengthen agency coordination to rebuild California’s salmon populations.
For more details, visit the Salmon Doubling Goal Performance Measure.
Why measure Restoration of Land-Water Connectivity?
A healthy and resilient ecosystem of the Sacramento-San Joaquin Delta requires the restoration of large areas at appropriate elevations that re-establish land-water connections allowing for frequent tidal and freshwater flooding. Frequent inundation of these restoring locations provides desired ecosystem functions such as increased aquatic food productivity and transfer of nutrients that benefit the native species of the Delta.
What happened in 2024?
Between 2014-2024, about 8,200 acres of tidal, riparian, and floodplain habitat were re-connected to tidal and freshwater flows by completing twenty-one ecosystem restoration projects.
Why is this important?
Historically, the Delta was a vast system of frequently flooded tidal marshes, wetlands, and floodplains. Although most of the natural wetlands no longer remain, some agricultural land, floodways, floodplains, and newly restored tidal wetlands can provide the desired ecosystem functions such as increased aquatic food productivity and transfer of nutrients that benefit the native species of the Delta.
What steps are being taken in 2025?
Delta Plan Five-Year Review recommended accelerating ecosystem restoration in the Delta. The Delta Plan set forth an updated set of strategies, policies, and recommendations to restore a healthy Delta ecosystem resilient to climate change. Delta Plan Interagency Implementation Committee established a Restoration Subcommittee tasked to increase community participation, improve interagency collaboration, streamline restoration implementation, coordinate funding, and plan for long-term management of restoring areas, all to increase the pace and scale of ecosystem restorations in the Delta.
For more details, visit the Seasonal Inundation performance measure.
Why measure Fish Passage?
The Delta serves as a migration corridor for all anadromous fish species in the Central Valley. Adult salmon migrate through the Delta as they return to the rivers they were born in. Young salmon use the Delta for their outmigration from the upstream rivers to the ocean for rearing and growing. Instream barriers to fish passage and unscreened water diversions impede migratory movements and adversely affect overall species survival.
What happened in 2024?
Remediation of Fish Barriers
As of 2024, 5 fish barriers were remediated out of the 57 identified in the 2018 baseline. An additional barrier was remediated that was included in a subsequent update of the CDFW barrier list. The following fish barriers were remediated:
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Antelope Creek Edwards Diversion (2018 baseline),
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Central California Traction Railroad Bridge (2018 baseline)
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Fremont Weir (2018 baseline)
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Knights Landing Outfall Gates (2018 baseline)
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Merced River Cowell Agreement Diverters (CAD) Wingdams (ID: 704924) (2018 baseline)
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North Fork Battle Creek Boulder Cluster Fish Passage (ID: 765176) (Post-2018)
Additional details and status can be viewed on DWR's website and the CalFish website linked in the data sources section in the Fish Passage performance measure page.
Central Valley Watershed Dams
Between 2018-2024, several efforts moved forward regarding the reintroduction of salmonids to their native historical habitat:
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On the Sacramento River:
- In 2022, Chinook Salmon were reintroduced above Shasta dam in the McCloud River as a response to the drought like conditions.
- In 2022, the California Department of Water Resources (DWR) received $1.5 million in funding for the Juvenile Salmonid Collection System Pilot Project (Juvenile Salmon Collection System) in the upper McCloud Arm of Shasta Lake —the first step of a program to return endangered Chinook salmon to their historical habitats. This program was also conducted in 2023.
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On the Yuba River:
- In 2023, CDFW, Yuba Water Agency, and NOAA announced an agreement to restore the Yuba River. This includes a new fishway to be built that bypass Daguerre Point Dam, modernizing water diversion, and a reintroduction plan for spring-run Chinook Salmon above New Bullards Bar Dam.
- In 2024, as part of the agreement described above, Salmon eggs were reintroduced to their historic habitat above New Bullards Bar Dam in the North Yuba River. The fish are part of project to study the feasibility of returning spring-run Chinook salmon to their historical spawning and rearing habitat in the mountains of Sierra County.
CDFW News | Pilot Project Returns Spring-Run Chinook Salmon to North Yuba River
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On the Feather River:
- In 2024, DWR conducted studies for the potential of returning spring-run Chinook salmon to historically available cold-water habitat in the Feather River Watershed above Lake Almanor.
Why is this important?
Removing fish passage barriers in the tributaries to the Delta is important because it restores migration corridors for salmon, restores aquatic habitat connectivity, and contributes to migratory fish recovery. Reintroduction of salmon above dams can provide access to their historic habitat, offer rearing habitat, spawning grounds, and refuge from warming temperatures due to climate change.
What steps are being taken in 2025?
Work continues on several fish passage barriers throughout the Delta watershed. On the Yuba River, along with continued work described above, reintroduction of Spring-Run Chinook Salmon is already occuring and work will continue throughout 2025.
For more details, visit the Fish Passage performance measure.
Why measure Invasive Species?
Invasive species are plants, animals, or invertebrates that are not native to the Sacramento-San Joaquin Delta, and once introduced and established, they reproduce and spread quickly, causing harm to the environment, economy, or human health. Invasive species are a major stressor to the Delta ecosystem as they take over habitat space, compete for food, alter food webs, modify the physical habitat structure, and prey upon native species.
What happened in 2024?
Golden Mussel
In October 2024, a new non-native invasive species was discovered in the Delta. The Golden Mussel (mussel) (Limnoperna Fortunei) was discovered at Rough and Ready Island near Stockton. The species have already been discovered throughout the Delta and south of the Delta at the San Luis Reservoir. Shortly after the discovery of the mussel, the California Department of Fish and Wildlife (CDFW) added the mussel to the list of restricted species from live importation, transportation, and possession. Placing the mussels on the restricted species list is an important step toward containment and prevention of further proliferation.
Nutria
Nutria is one of the recently introduced invasive species and is being managed to prevent establishment. In 2024, a total of 1,353 nutria were removed throughout the state, an annual high since the program began in 2017 (previous high was in 2020) and almost doubling 2023’s total take of 678. Within the Delta, a total of 361 nutria were taken since December 2023, accounting for roughly half the total take since 2017 of 685. As of January 2025, a total of 5,448 nutria were taken statewide,
The map below shows the locations and density of nutria taken in the Delta and Suisun Marsh in 2024.
Why is this important?
Golden Mussel
The discovery of the mussels is the first known occurrence in North America. The species poses a significant threat to natural ecosystems, infrastructure, and water quality in California. These mussels have similar impacts to the invasive Zebra and Quagga Mussels, which are established elsewhere in the United States such as the Great Lakes and the Colorado River basin and in Southern California.
Nutria
The number of nutrias found within the legal Delta has significantly increased, with more than half of total nutria taken in 2024. Nutria are large semi-aquatic rodents that breed prolifically and can damage water conveyance and flood infrastructure, vulnerable wetland habitats, and agriculture.
What steps are being taken in 2025?
Golden Mussel
CDFW is coordinating with state, federal, and local entities to create a statewide response plan that strategizes best approaches to minimize further spread of the mussels within California and the U.S. Monitoring of the mussels are ongoing and will expand to include other waterbodies that were not regularly monitored for invasive mussels.
Regular updates on invasive golden mussel in California are provided on CDFW’s website.
Nutria
The California Department of Fish and Wildlife (CDFW), in collaboration with other agencies, continues the nutria eradication program with the goal of eradicating the population in California.
Regular updates on invasive nutria control in California are provided on CDFW’s website.
For more information, visit the invasive species performance measure.
Why measure Subsidence Reversal?
Land subsidence is a key issue affecting many aspects of the Sacramento-San Joaquin Delta management; it makes adjacent levees less stable, increases flood risks, causes farming soil loss, and releases vast quantities of carbon dioxide into the atmosphere. Subsidence can be reversed through a slow accumulation of new sediments on managed wetlands and mixed wetland-rice farms. Subsidence reversal projects can also sequester carbon allowing them to take advantage of carbon credit markets while helping California meet its greenhouse gas reduction targets.
What happened in 2024?
By 2024, sustainable land management practices that rebuild soil, reverse land subsidence and sequester carbon covered only about 3,300 acres. However, new projects are in the planning phases, enabled by funding from the Sacramento San Joaquin Delta Conservancy (Delta Conservancy) and others that will provide additional subsidence reversal and rice conversion activities. These new projects will add about 11,000 acres addressing the land subsidence and are estimated to result in about 110,000 metric tons per year of avoided carbon emissions.
Why is this important?
Much of the Delta is sinking due to a process called subsidence which is caused by the drainage of Delta wetlands and the subsequent oxidation of peat soil. This results in elevation loss and the release of carbon dioxide. In some areas of the Delta, the land has subsided to 25 feet below sea level.
What steps are being taken in 2025?
Delta Plan Five-Year Review recommended accelerating subsidence reversal efforts in the Delta and supporting the Delta Conservancy in their coordination with the California Air Resources Board (CARB), DWR, and others to make subsidence activities more economically viable and securing funding for landowners to offset the conversion cost into rice and wetlands.
The Delta Independent Science Board is conducting a review of the science to inform the management of subsided lands and is anticipated to release the report in 2025.
For more information, please visit the Subsidence Reversal performance measure.
Why measure Salinity?
As Pacific Ocean saltwater flows into the Sacramento-San Joaquin Delta, the freshwater mixes with ocean water and salinity levels change. If too much saltwater enters the Delta, it can reduce the quality of the water used for agricultural and municipal purposes and harm native species. Drought conditions exacerbate salinity conditions by reducing freshwater river flows into the Delta. Compliance stations are set up around the Delta to monitor and report salinity levels.
Additionally, a low salinity habitat in the Delta, referred to as X2, is designed to support the native fish of the Delta, specifically the Delta and longfin smelt. X2 is the location from the Golden Gate Bridge where water salinity is 2 ppt (parts per thousand) of isohaline salt.
What happened in 2024?
In 2024, Fall X2 was maintained at the required 80 km from the Golden Gate Bridge during September. Operating the Suisun Marsh Salinity Control Gates by the Department of Water Resources daily in September provided alternative habitat conditions for native smelt and allowed for relaxation (amendment) of the October X2 target requirement in 2024.
Water quality compliance for salinity was maintained at all compliance monitoring stations during the year 2024 within the Delta and Suisun Marsh.
Why is this important?
Salinity in the Delta is an important water quality characteristic affecting municipal, industrial, agricultural, and fish and wildlife water uses. When salinity exceeds compliance conditions or changes too rapidly, it can have negative impacts on many beneficial uses of water. Water management agencies must comply with existing flow and salinity objectives to protect the beneficial uses of Delta water.
What steps are being taken in 2025?
In 2024, updated United States Fish and Wildlife Service's Biological Opinions took effect for the long-term operations of the State Water Project and the Central Valley requiring the California Department of Water Resources and the Bureau of Reclamation to maintain an average of 80 km or less from the Golden Gate in “above normal” and "wet” years for September through October. It also included other measures, such as the operation of the Suisun Marsh Salinity Control Gates and fish food enhancement actions, that are expected to achieve ecological benefits.
Additionally, the State Water Resources Control Board is updating the Bay-Delta Water Quality Control Plan which establishes water quality control measures and flow requirements needed to provide reasonable protection of beneficial uses in the watershed.
For more information, visit the Salinity performance measure.
Why measure Harmful Algal Blooms?
Harmful algal blooms (HABs) are a persistent issue in the Sacramento-San Joaquin Delta. The region is located near major urban areas and agricultural hubs, and together with its low flowing and winding channels, and warming temperatures, it presents environmental conditions conducive to HABs.
What happened in 2024?
In 2024, summer conditions in the Delta were normal and despite higher-than-normal temperatures, HABs were not widespread based on incidental reporting and occurred in areas that are regularly monitored for HABs presence (such as Discovery Bay). Satellite data that are used for screening cyanobacterial densities also show reduced high-density formations throughout the larger Delta waterbodies.
Why is this important?
Consistent monitoring of HAB toxins is important for understanding the extent and causes of HABs and for informing mitigation approaches. A Delta Cyanobacteria Harmful Algal Blooms Monitoring Strategy (Strategy) was released in 2024 to establish a monitoring program for Cyanobacteria HABs in the Delta, coordinate the collection of priority data, promote data-sharing, and identify feasible mitigation techniques for reducing HAB prevalence.
What steps are being taken in 2025?
The strategy details near-term recommendations to implement such as:
“Recommendation 1.1 Identify co-chairs or mechanism for leadership of coordination and implementation of the Strategy and Recommendation 1.2 Form CHABs Working Group to develop final goals, management questions, and monitoring strategy and prioritize special studies”
In addition, continued monitoring, special studies, and incident reporting of HABs continues.
For more details, visit the HABs performance measure.