Our Water Supply

Image of Imported Water Sources Map

WHY IS THERE ANYTHING IN MY WATER?

The sources of drinking water (both tap water and bottled water)include rivers, lakes, streams, ponds, reservoirs, springs and wells. As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and, in some cases, radioactive material, and can pick up substances resulting from the presence of animals or from human activity. Contaminants that may be present in source water include:

  • Microbial contaminants, such as viruses and bacteriathat may come from sewage treatment plants, septic systems, agricultural livestock operations, and wildlife.
  • Inorganic contaminants, such as salts and metals, that canbe naturally occurring or result from urban storm water runoff, industrial or domestic wastewater discharges, oil and gas production, mining, or farming.
  • Pesticides and herbicides that may come from a varietyof sources such as agriculture, urban storm water runoff, and residential uses.
  • Organic chemical contaminants, including synthetic andvolatile organic chemicals that are by-products of industrial processes and petroleum production, and can also come from gas stations, urban storm water runoff, agricultural application, and septic systems.
  • Radioactive contaminants that can be naturally occurringor be the result of oil and gas production and mining activities.
Image of Treatmant Plant Service Area Map

Your water comes from three municipal water
treatment plants - Alvarado, Miramar and Otay.
The City maintains nine reservoirs and purchases
imported water from the San Diego County Water Authority.
Water from the Colorado River Aqueduct and the State
Water Project, as well as some local runoff,
constitute the source waters for these plants.

In order to ensure that tap water is safe to drink, the U.S.Environmental Protection Agency and the State Water Resources Control Board (State Board) prescribe regulations that limit the amount of certain contaminants in water provided by public water systems. State Board regulations also establish limits for contaminants in bottled water that provide the same protection for public health.

Treatment Plant Service Areas

Your water is treated atthree municipal water treatment plants ? Alvarado, Miramar and Otay. The City maintains nine reservoirs and purchases imported water from the San Diego County Water Authority. Water from the Colorado River Aqueduct and the State Water Project, as well as some local runoff, constitute the source waters for these plants. A small amount of treated water is also imported from the MWD Skinner Treatment Plant.

OUR IMPORTED WATER SUPPLY AND THE IMPACT ON WATER QUALITY

The City of San Diego imports an average of 85 percentof its water supply. This imported water is provided by the San Diego County Water Authority, which purchases water from the Metropolitan Water District of Southern California. Ultimately, our imported water is a blend of Colorado River water and State Water Project water (see map). Throughout the year, the blend changes.

Several forces negatively impact the quality of waterfrom the Colorado River and State Water Project. The Colorado River winds through thousands of miles of unprotected watershed containing towns, farms, old mining sites and industrial sites.

Water from the State Water Project is also subject topotential contaminants such as pesticides and herbicides. This water source also has a higher organic carbon and bromide level than the Colorado River water. As organic carbon and bromide levels increase, the potential for creating higher levels of disinfection by-products exists. The City continually alters its treatment process to adjust for changing water supplies.

The City of San Diego regularly monitors the quality of ourwater to ensure all drinking water quality standards are met.

Imported Water Sources

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