Dissolved Oxygen

Outcome Performance Measure 6.5, Last updated: April 15, 2024 | About this Measure
In water year 2023, 34 out of the 38 monitoring stations in the Sacramento-San Joaquin Delta that recorded dissolved oxygen met their specific daily targets.

The Measure

Applicable dissolved oxygen (DO) standards in the Delta and Suisun Marsh are consistently met.

  • Expectations

    Applicable dissolved oxygen (DO) standards in the Delta are consistently met.

  • Performance Metrics

    • Milligrams of DO per liter of water (mg/L).
    • Continuous, real-time DO measurements made at multiple locations throughout the Delta.

Delta Monitoring Stations

The map below shows the stations that recorded 15-minute intervals for dissolved oxygen (DO) in the Delta. The bar graph shows the number of days that a station missed the daily standard of 5 mg/L or their respective standard for DO for each water year.

  • A red point represents a station that missed the target of a daily average of 5 mg/L of DO or their specific DO standard for water year 2023.
  • A blue point represents a station that met the specific DO targets for water year 2023.

Some monitoring stations may not be displayed due to a lack of data for that specific water year. Click on the points to view how many days a station missed the target. You can zoom in on the map by pressing ctrl + scrolling on your mouse.

Locations of DO monitoring stations

*A note about station SDO: Station SDO water quality objectives change from 5mg/L daily average from December to August to 6 mg/L daily average from September through November in the San Joaquin River between Turner Cut and Stockton. The data in the map above for station SDO is only from one of three sensors (sensor #61). Other DO sensors (#201, 202) for station SDO showed an exceedance of the water quality objective between September and October. Additional details can be found on the Central Valley Water Board's Executive Officer's Report_December 2023 (ca.gov).

Suisun Marsh Monitoring Stations

The map below shows the stations that recorded 15-minute intervals for DO in Suisun Marsh. The bar graph shows the number of days that a station missed their respective chronic and acute standards. Additional information regarding the Suisun Marsh DO standards can be viewed in the accordion below and on the State Water Board's website: Suisun Marsh TMDL (ca.gov).

Some monitoring stations may not be displayed due to a lack of data for that specific water year. Click on the points to view how many days a station missed the target. You can zoom in on the map by pressing ctrl + scrolling on your mouse.

Next Data Update: Dissolved oxygen is regularly recorded in 15-minute intervals at several stations available via California Data Exchange Center. The next data update for this visualization will be in 2025.

Monitoring Stations

For a full list of stations and water quality data, please visit: DWR's California Data Exchange Center.

Dissolved oxygen water quality objectives ensure aquatic organisms receive minimum dissolved oxygen requirements for optimal growth and life support. Meeting dissolved oxygen water quality standards will help prevent negative effects to wildlife. For example, dissolved oxygen concentrations in the Stockton Deep Water Ship Channel and Old and Middle Rivers can drop to inhospitable conditions during warmer and lower water flow periods. In Suisun Marsh, the decay of plant matter in late summer and early fall causes severe dissolved oxygen depletion. Low concentrations of dissolved oxygen can adversely affect aquatic life, including the health and migration of native fish such as salmon.

Several actions taken to comply with the minimum dissolved oxygen requirements, along with improved water flow and a reduction of pollution loads in the San Joaquin watershed appear to have provided a solution to this water quality problem. Consistently meeting the dissolved oxygen levels above the minimum recommended levels specified in the Sacramento River and San Joaquin River Basins and San Francisco Bay Water Quality Control Plans will benefit the Delta ecosystem by providing optimal living conditions to native aquatic wildlife.

The San Francisco Bay Regional Water Quality Control Board (Region 2) adopted the Total Maximum Daily Load (TMDL) for dissolved oxygen in Suisun Marsh in April 2018, followed by State Water Resources Control Board (SWRCB) adoption in August 2018. The California Office of Administrative Law (OAL) approved the regulatory action in November 2018 and the U.S. Environmental Protection Agency (USEPA) approved the Basin Plan amendment to establish the TMDL and the site-specific objectives for dissolved oxygen in July 2019. The objectives protect sensitive fish species and take into consideration the different spatial and temporal variability of dissolved oxygen in the Suisun Marsh.

Each chapter of the Delta plan includes strategies to achieve the goals of the plan. These strategies are general guidance on achieving the objective laid out in the plan and in the Delta Reform Act of 2009. Associated with these strategies are recommendations. The recommendations describe more specific and implementable actions to support the achievement of Delta Plan strategies. Strategies and recommendations may also have associated performance measures. Delta Plan performance measures track progress in achieving desired outcomes for the Delta Plan. Below are the strategies and recommendations associated with this performance measure.

Delta Plan Strategy

  • Improve environmental water quality

Delta Plan Recommendations

  • Completion of regulatory processes, research, and monitoring for water quality improvements
  • Implement Delta Regional Monitoring Program
  • Evaluate wastewater recycling, reuse, or treatment
  • Manage dissolved oxygen in Stockton Deep Water Ship Channel
  • Manage dissolved oxygen in Suisun Marsh
Metric
  • Milligrams of DO per liter of water (mg/L).
  • Continuous, real-time DO measurements made at multiple locations throughout the Delta.
Baseline
  • Measured as of the date of the Delta Plan’s adoption, May 2013.
Target
  • Meet water quality objectives for DO in the Stockton Deep Water Ship Channel, Suisun Marsh, and Old and Middle Rivers.
  • Maintain or exceed the minimum DO concentrations of:
    • 5 mg/L daily average everywhere in the Delta.
    • 6 mg/L daily average from September through November in the San Joaquin River between Turner Cut and Stockton.
Methods

Dissolved Oxygen (DO) is obtained through DWR's monitoring stations. 15-minute interval data was collected and then used to average daily DO levels. Monitoring data is available through DWR's CDEC website.

Data Source:
California Data Exchange Center

 

Disclaimer

When using data, please use the original source data. Just like the source data, the data are provisional and are subject to change. Data collected were as of May 2013 or the earliest date the station went online.

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