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 2023.


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.

2023 Conditions

In 2023, California illustrated the extremes of its climate, jumping from a prolonged three-year drought during 2020-2022 to a wet winter in 2023. California’s Governor issued two weather-related Emergency Proclamations in short succession: an executive order for drought conditions (in effect 2021- early 2023) and a state of emergency proclamation due to the 2023 winter storms. Performance measures featured below describe conditions in 2023 including water supply reliability, water quality, habitat restoration, Delta levees, flood insurance, and invasive species.

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 2023?

The California Department of Water Resources (DWR) reported on the status of 2020 Urban Water Management Plans (UWMPs) to the legislature and conducted an analysis for reduced Delta reliance and improved regional self-reliance. The 2020 UWMP guidebook provided a methodology for documenting reduced Delta reliance as a voluntarily element within UWMPs. DWR’s presentation to the Council (November 2023) summarized that out of the 238 UWMPs that receive Delta water, 22% of plans analyzed reductions in reliance on Delta water and 73% showed improvements in regional self-reliance. Additionally, in 2023, the State Water Resources Control Board hosted a workshop regarding the Making Conservation a California Way of Life proposed regulatory framework. This framework would establish additional water use efficiency goals based on uniqueness and flexibility of locally appropriate solutions and potentially reduce urban water use by more than 400-thousand-acre feet by 2030, helping California adapt to the water supply impacts of climate change.

Why is this important?

Reducing individual demand for water improves regional self-reliance and supports reduced reliance on the Delta. Subsequently, reporting the urban water suppliers’ reliance on Delta water is important for understanding how to better achieve water supply reliability and reduced reliance on Delta water.

What steps are being taken in 2024?

In 2024, the State Water Resources Control Board will be providing additional opportunities for the public to provide input. Adoption of the regulation is anticipated in summer 2024. If adopted, the regulation will be effective in fall 2024.

For more details, visit the Urban Water Use performance measure.

Why track agricultural water planning?

Agricultural water suppliers must comply with water planning and measurement laws and submit their Agricultural Water Management Plans (AWMPs) to the California Department of Water Resources (DWR) every five years as required by the California Water Conservation Act of 2009 (SB X7-7) and the Water Management Planning Act of 2018 (AB 1668). Agricultural water suppliers report annually on aggregated water deliveries to farms. Monitoring improvements in agricultural water use supports a reliable water supply for all Californians.

What happened in 2023?

DWR completed an evaluation of AWMPs of water suppliers that irrigate 25,000 or more acres. In the evaluation, twenty-five out of the twenty-seven California agricultural water suppliers that were required to submit an AWMP included quantification of water use efficiency (WUE). In addition, seven out of the ten agricultural water suppliers that receive State Water Project (SWP) water include an explicit accounting of reduced water use from the Delta. This evaluation was presented to the Council in November 2023.

Why is this important?

WUE is key to maximizing beneficial uses of water. Tracking and reporting WUE can help identify where efficiency improvements can be made. Improvements in WUE can be used to irrigate more crops, recharge groundwater, and for environmental use.

This initial analysis of ten agricultural water suppliers that receive SWP water is important as it represents a potential approach to reducing Delta reliance. Reduced Delta water reliance is one of the Delta Reform Act’s goals for achieving a reliable water supply for California.

What steps are being taken in 2024?

Agricultural water suppliers calculate water budgets annually and will report their agricultural water use efficiencies to the California Department of Water Resources in the next AWMP submission cycle in 2025.

For more details, visit the Agricultural Water Planning performance measure.

Why measure restored habitat?

Restoring large areas of natural communities provides functional, diverse, and interconnected habitats suitable for fish and other wildlife, and contributes to a healthy Delta ecosystem resilient to a variable climate. The Delta Plan sets targets to increase areas with natural communities. Measuring progress toward these targets is important for understanding if restoration activities are occurring at a scale and pace needed to support native species and a healthy ecosystem.

What happened in 2023?

Evaluation of vegetation conditions in the 2016 Vegetation Classification and Mapping Program (VegCAMP) (the most recent data available) reveals that restoration progress for tidal wetlands and riparian habitats has been slow. Restoration activities increased since 2016. Restoration projects completed between 2016-2022) added over 5,300 acres of tidal wetlands, over 2,000 acres of seasonal and nontidal wetlands, and over 700 acres of riparian habitat. Additionally, in 2023, another 5,000 acres of restoration projects were in progress and 6,000 acres were being planned.


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Why is this important?

It is important to provide a short-term assessment of progress toward the restoration targets to show how many additional acres need to be restored at sufficient scale and in appropriate locations to provide for functional, diverse, and interconnected habitats.

What steps are being taken in 2024?

The Delta Plan Ecosystem amendment sets new and revised policies, recommendations and performance measures for achieving a dynamic and resilient restored Delta landscape. The Council leads the Delta Plan Interagency Implementation Committee (DPIIC), and together with the Delta Conservancy facilitates the DPIIC Restoration Subcommittee to improve agency coordination, accelerate implementation of ecosystem projects, and expedite restoration of large areas of natural communities.

For more details, view Acres of Natural Communities Restored performance measure.

Why measure Invasive Species?

Invasive species are plants, animals or invertebrates that are not native to the 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 because they can take over habitat space, compete for food, alter food webs, modify the physical habitat structure, and prey upon native species.

What happened in 2023?

Invasive Nutria

Nutria is one of the recently introduced invasive species and is being controlled to prevent establishment. In 2023, a total of 678 nutria were removed throughout the state, with 184 in the Delta (Sherman Island) and Suisun Marsh. Detections and removal of nutria in the Delta increased in 2023 compared to previous years. As of December 2023, a total of 4,057 nutria were taken statewide, with 317 taken from the legal Delta since the start of the program in 2017. The map below shows the locations and density of nutria taken in the Delta and Suisun Marsh in 2023.


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Invasive Species Prevention

Other known invasive species occurring elsewhere in California were prevented from establishing in the Delta due to rigorous surveillance, prevention, and education, including Quagga/Zebra Mussels, Water snakes (Nerodia sipedon), and Mute swans.  

Why is this important?

The number of nutria found within the legal Delta has significantly increased, with more than half of total nutria taken in 2023. 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 2024?

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. In addition, the Delta Interagency Invasive Species Coordination Team continues to work towards an Early Detection and Rapid Response (EDRR) system for the Delta region. EDRR is key to address new introductions of nonnative invasive species from becoming established in the Delta.

Regular updates on invasive nutria control in California are provided on CDFW’s website.

For more details, view invasive species performance measure.

Why measure Groundwater Quality?

Groundwater wells used for domestic and municipal water supply that exceed arsenic and/or nitrate drinking water limits in the Delta are water quality issues and are possible indicators of other more serious contaminants. This is especially true for small water systems and disadvantaged communities that are highly dependent on groundwater sources that may not meet certain drinking water quality standards. Sources of nitrate and arsenic contamination can come from both natural and man-made sources. Consumption of high levels of nitrate and arsenic has various long- and short-term health effects.

What happened in 2023?

Analysis of 2018-2022 data shows that 11% of the domestic and municipal groundwater wells exceeded the nitrate limits (32 wells out of 303 sampled), and about 32% exceeded the arsenic limits (59 wells out of 185). Contamination of domestic and municipal groundwater wells with elevated nitrate and arsenic levels continues to be an issue.

Why is this important?

Reducing the number of wells exceeding nitrate and arsenic limits is important to provide safe drinking water for people who depend on groundwater wells. High nitrates and arsenic levels in drinking water can lead to serious health issues, especially for children and pregnant women.

What steps are being taken in 2024?

Since 2021, the Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) has been implementing a program that provides free well testing and safe drinking water to residents whose wells are impacted by nitrates. In 2024, the program is moving into its next phase, in which eight other groundwater basins, including two within the legal Delta, will be served by the program (the eastern San Joaquin and Yolo basins).

Additional information: Home - CV SALTS (

GAMA continues to share available data and information on its homepage: The Groundwater Ambient Monitoring and Assessment (GAMA) Program | California State Water Resources Control Board.

For more details, view Groundwater quality performance measure.

Why measure the level of flood protection?

Delta levees protect low-lying islands and tracts and play a key role in flood risk reduction. Tracking the number of rural and urban levees meeting applicable design standards is important because it can indicate weak points in the flood protection system and can highlight areas where investments are needed.

What happened in 2023?

Between 2012 – 2023, the level of compliance with Bulletin 192-82/PL 84-99 standards for rural islands increased from ~27% in 2012 to 31% in 2023. This means that about 30% of the Delta rural islands are protected by levees meeting the applicable flood protection standard.  Urban levees in the Delta must provide 200-year flood protection. Levee improvements were completed on urban levee sections in Stockton and West Sacramento. Despite these improvements, Delta urban islands do not meet the applicable standard (0 out of 6 islands meeting 100% urban levee design standards).

Why is this important?

2023 was a wet year in California, with two large flooding events that triggered a federal disaster proclamation. Despite this, there were no significant Delta levee failures. Delta levees continue to provide reliable flood protection, reducing flood risks to people and property.

What steps are being taken in 2024?

The Council has adopted the Delta Levees Investment Strategy (DLIS), which became California state law on January 1, 2024. DLIS sets a risk-based prioritization for levee investments in the Delta. The California Department of Water Resources funds levee projects through multiple programs and annually reports to the Council on its investments in Delta levees.

For more details, view Delta levees performance measures.

Why measure Community Rating Scores?

Measuring Community Rating Scores in the Delta is important because it serves as an indication of the limited state liability strategy outlined in the Delta Plan and Delta Reform Act of 2009. The Community Rating Score (CRS) system allows a community to show documentation of flood-proofing actions to get a discount on Federal Emergency Management Agency (FEMA) National Flood Insurance Program premiums.  Because of the connection between floodproofing activities and CRS scores, measuring Community Rating Scores can also indicate Delta communities’ investments in floodproofing efforts and how much a community is investing in specific floodproofing categories.

What happened in 2023?

Eleven Delta communities and counties qualified for NFIP discounts between 2013 and 2023. On average, Delta communities improved their CRS rating by 4% between 2013-2023, lowering the cost of the National Flood Insurance Program for its residents. Open Space Preservation as a flood-proofing activity contributed most to improving CRS ratings across these communities.

Why is this important?

This finding is important because it indicates that the target set for this metric of a one percent increase in Community Rating System credit points by 2025, has been achieved earlier than anticipated.  The City of Sacramento and Sacramento County lead this trend in the Delta, with hundreds of points earned over the past 10 years. This finding is significant given that the state of California has seen a decline in NFIP enrollment in recent years.

What steps are being taken in 2024?

Some Delta Communities are part of CRS Users Groups which provide helpful resources and tips for maximizing a community’s CRS points and NFIP discounts. The next data update from FEMA is expected in the next 3 to 5 years.

For more details, visit the Flood Insurance Community Ratings performance measure.