Beach Water Quality

Locals and tourists alike value the San Diego region in part for its safe, accessible, and clean beaches. However, occasionally, water quality problems force their closure. To protect the health of local and visiting beach goers, the County of San Diego Department of Environmental Health and Quality’s (DEHQ) Beach and Bay Water Quality Program monitors beach water quality and posts advisories, warnings, and closures when necessary.[1]
By state law, the water at beaches that receive both 50,000 annual visitors and have stormwater fallout are monitored at least weekly from April to October.[2] The frequency of San Diego’s beach water quality monitoring exceeds the standards set by the state, with daily monitoring of south county beaches. When bacteria exceed state standards or the water is contaminated with sewage or chemicals, either an advisory, warning, or closure is issued. An advisory is issued when testing detects hazardous bacteria that exceed state thresholds. A warning is issued when currents push contaminated water north over the border from Mexico. An affected area is closed when there is known sewage or a sewage spill. The bacterial contaminants that caused beach closures in San Diego County beaches in 2021 include E. Coli, Enterococcus, and other fecal coliforms[3] which can cause diseases of the skin, eyes, ears, respiratory system, and digestive system.[4]
In San Diego County, advisories and closures commonly result from three types of events: storm water run-off bringing contaminated water to beaches, hazardous spills into beach water, or weather patterns bringing water with high bacterial levels close to shore.[5],[6] While weather-related closures are difficult to mitigate because of their unpredictability, local and federal governments are working together on programs that could, over the course of several years, decrease the impact of sewage on San Diego County beaches.[7]
Using 2021 data from the California State Water Resources Control Board[8] for San Diego County beaches, the figure below lists the number of days affected by closures or advisories at each site. Rain advisories are not included because they are often based on whether it has rained and not on evidence of contamination.[9]
Data show that water quality issues were not evenly distributed across the county because of varied geographic, environmental, and infrastructural features. For example, south county beaches, such as Border Field State Park and Imperial Beaches, were disproportionately affected by beach closures due to runoff from the Tijuana River and ocean patterns that bring sewage north from the San Antonio de los Buenos Treatment Plant in Mexico.
In May of 2022, the San Diego County Department of Environmental Health and Quality became the first coastal county to use a new, faster, and more accurate test for fecal indicator bacteria. This change will protect more beach visitors and provide the public with more accurate and timely information about beach water quality.

Data Information
Data Source: California State Water Resources Control Board, 2021.
  1. San Diego County. (2022). Beach and Bay Program. Retrieved July 19, 2023.
  2. California State Water Resources Control Board. (n.d.). Beaches—California Beach Water Quality Background Information. Retrieved March 7, 2023, from
  3. California State Water Resources Control Board. (2023). Search Beach Monitoring Data, Monitoring Data Search. Retrieved March 7, 2023, from
  4. U.S. EPA. (2013, September 3). Indicators Used in the National Aquatic Resource Surveys [Collections and Lists]. Retrieved from
  5. San Diego County Environmental Health and Quality (n.d.). Beach and Bay Program. Retrieved August 10, 2023, from
  6. California State Water Resources Control Board. (2018). Beaches - California Beach Water Quality Background Information. Retrieved March 7, 2023, from
  7. Regional Leaders Announce Settlement in Tijuana River Valley Sewage Litigation | City of San Diego Official Website. (n.d.). Retrieved June 23, 2023, from
  8.  California State Water Resources Control Board. (2023). Search Beach Monitoring Data, Beach Advisory Search. Retrieved from
  9. California Water Boards. (n.d.). Frequently Asked Questions. Retrieved March 8, 2023, from
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Updated February 7, 2024