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California Water Quality
1,182
Utilities in database
36.4M
Residents served
15%
On private wells
4
Key contaminants tracked
Drinking Water in California
California's drinking water comes from a complex mix of surface water (rivers, reservoirs) and groundwater. The state has some of the strictest water quality regulations in the U.S., but still faces challenges from agricultural runoff, legacy industrial contamination, and aging infrastructure in older cities. The State Water Resources Control Board maintains primacy for Safe Drinking Water Act enforcement.
Utilities in California
Top 20 of 1,182 by populationLOS ANGELES-CITY, DEPT. OF WATER & POWER
CA1910067 · 7,751,132 served
EAST BAY MUD
CA0110005 · 1,442,800 served
SAN DIEGO, CITY OF
CA3710020 · 1,385,379 served
SAN JOSE WATER
CA4310011 · 1,039,920 served
SFPUC CITY DISTRIBUTION DIVISION
CA3810011 · 848,019 served
EASTERN MUNICIPAL WD
CA3310009 · 666,581 served
CITY OF FRESNO
CA1010007 · 545,716 served
CITY OF SACRAMENTO MAIN
CA3410020 · 527,979 served
LONG BEACH UTILITIES DEPARTMENT
CA1910065 · 466,772 served
IRVINE RANCH WATER DISTRICT
CA3010092 · 444,800 served
CITY OF ANAHEIM
CA3010001 · 348,593 served
ALAMEDA COUNTY WATER DISTRICT
CA0110001 · 344,000 served
CITY OF SANTA ANA
CA3010038 · 310,539 served
RIVERSIDE, CITY OF
CA3310031 · 298,398 served
SANTA CLARITA VALLEY WATER AGENCY
CA1910240 · 294,090 served
GSWC - SOUTHWEST
CA1910155 · 277,740 served
HELIX WATER DISTRICT
CA3710010 · 277,668 served
COACHELLA VWD: COVE COMMUNITY
CA3310001 · 270,000 served
CWS - BAKERSFIELD
CA1510003 · 267,881 served
SAN GABRIEL VALLEY WATER CO.-EL MONTE
CA1910039 · 248,000 served
Key Contaminant Concerns in California
PFAS
Per- and polyfluoroalkyl substances (PFAS) are a class of over 12,000 synthetic chemicals characterized by strong carbon-fluorine bonds that resist degradation. The two most studied — PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) — have been phased out of U.S. manufacturing but persist widely in the environment.
Nitrates
Nitrate (NO₃⁻) is a nitrogen-containing compound that forms naturally through the decomposition of organic matter. At elevated concentrations — almost always from human activity — nitrate interferes with the blood's ability to carry oxygen. The United States produces over 23 million tons of nitrogen fertilizer annually, making agricultural runoff the dominant source of nitrate contamination.
DBPs
When utilities add chlorine to water to kill pathogens, it reacts with dissolved organic matter — leaves, algae, soil — to produce disinfection byproducts (DBPs). Over 600 DBPs have been identified. The EPA regulates two groups: total trihalomethanes (TTHMs, including chloroform) and haloacetic acids (HAA5). DBP levels tend to be highest in surface water systems and in warm months when organic matter is elevated.
Arsenic
Arsenic (As) occurs naturally in rock and soil, dissolving into groundwater through natural weathering processes. Inorganic arsenic — the form found in drinking water — is a known human carcinogen. The western United States has particularly arsenic-rich geological formations, but elevated levels have been found in 48 states. Arsenic is tasteless and odorless.
California Water FAQs
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Data source: Utility data from EPA SDWIS. 1,182 active community water systems ingested. CCR contaminant data ingestion in progress.
Last updated: 2025-01-10