California’s 40 million residents, the farmers who produce $50 billion a year in agricultural commodities, the industry that helps power the fifth-largest economy in the world and the plants, fish and wildlife that are a vital part of the state’s environment all depend on clean water to survive.

Surface waters, however, are threatened by a host of pollutants, such as bacteria, trash and agricultural runoff. Groundwater in California also can be contaminated by nitrates and legacy chemicals from military and industrial uses that seep from the land above. [See also How is Drinking Water Treated?]

Perhaps the greatest threat to surface water is nonpoint sources of pollution, such as runoff from agricultural fields and abandoned mines, and stormwater runoff from city streets and construction sites.

Stormwater is typically not treated before it is discharged, so it can contain a variety of contaminants such as pesticides, nitrates from fertilizers, pathogens from animal waste, and automotive and industrial chemicals. Stormwater flows to rivers, bays and the ocean.

Microplastics – plastic debris measuring less than 5 millimeters that come from a variety of consumer products – are an increasing water quality concern. They enter the water as industrial microbeads or as larger plastic litter that degrade into small pellets.

Microplastics come from microbeads that are used as exfoliating agents in cosmetic washes and large-scale cleaning processes. They are also used pharmaceutically for efficient drug delivery and by textile companies to create artificial fibers. Part of their appeal to hygienic and medical interests is their tendency to absorb surrounding chemicals and later release them. This quality makes microplastics ideal as small commercial sponges, but especially dangerous as water contaminants, potentially carrying harmful chemicals through the food chain as they are ingested by fish and other animals. In 2021 the State Water Resources Control Board (State Water Board) issued a draft policy that would require water agencies to test for microplastics in drinking water.

Water Quality Regulation in California

Water quality in California is regulated by several state agencies, including the State Water Board and its nine regional boards – North Coast, San Francisco Bay, Central Coast, Los Angeles, Central Valley, Lahontan, Colorado River Basin, Santa Ana and San Diego.

The State Water Board enforces clean water laws and administers the Clean Water Grant Program, which funds construction of wastewater treatment facilities. The State Water Board also issues general permits for municipalities and construction sites aimed at preventing contaminants from entering municipal storm sewers.

The State Water Board’s updated Bay-Delta Water Quality Control Plan for the Lower San Joaquin River and Southern Delta is based on the premise that increased flows allowed to stay in the river rather than diverted for human use will improve water quality. But the plan also allows for reduced river flows on tributaries where stakeholders have reached voluntary agreements to pursue a combination of flow and non-flow measures that improve environmental conditions.

Drinking Water Quality

Drinking water standards and regulations are developed by federal and state agencies to protect public health. The federal Safe Drinking Water Act (SDWA) regulates drinking water quality on the national level. Due to the stringent drinking water quality standards in California, the U.S. Environmental Protection Agency allows the state to administer the SDWA. The State Water Board’s Division of Drinking Water regulates public drinking water systems.

In California, many disadvantaged communities in isolated areas and in urban parts of the state do not have access to safe drinking water. It’s been estimated that more than 1 million people in the state regularly lack access to clean drinking water at home, work or school.

With strict and increasing regulations on water quality, high costs of water system maintenance or lack of technical knowledge to apply for grant funding, many disadvantaged regions are at a loss in making substantial water quality and infrastructure improvements.

In 2012, Gov. Jerry Brown signed Assembly Bill 685, making California the first state in the nation to legislatively recognize the human right to “safe, clean, affordable, and accessible water adequate for human consumption, cooking, and sanitary purposes.” In 2016, the State Water Board adopted a resolution identifying the human right to water as a top priority and core value for it and each of the state’s nine regional water quality boards. In 2019, Gov. Gavin Newsom signed into law the Safe and Affordable Drinking Water Fund to financially support local water systems in providing safe drinking water.