Water systems located in nearly every California county are at risk of failing, according to a map created by Newsweek using data from the California State Water Resources Control Board. The board's annual report, released in June, evaluates the stability of water-treatment systems amid growing concerns over cyberattacks and new Environmental Protection Agency (EPA) requirements for per- and poly-fluoroalkyl substances (PFAS) levels in the water supply.

Although PFAS levels are not yet part of the criteria used to assess water systems, a spokesperson for the board indicated that such criteria would likely be included in the coming years. Currently, the board's evaluation includes factors such as E. coli violations and water systems' inability to consistently provide adequate water due to drought conditions.

Based on these criteria, 613 public water systems in California are at risk of failing as of January 1 of this year. The map of at-risk drinking water systems shows that these vulnerable systems are spread throughout the state, with the highest concentrations in Tulare, Kern, and Los Angeles Counties. Only Lassen, Modoc, and San Francisco Counties were without at-risk water systems.

The report highlights that while 61 percent of California's 3,055 public water systems are not at risk, 20 percent are considered at risk, and 14 percent are potentially at risk. Notably, small systems in rural areas are most affected, comprising 512 of the at-risk systems. Additionally, 34 medium-sized systems and 70 K-12 schools are classified as at-risk, with 47 K-12 schools receiving water from failing systems. Some prisons and city providers also rely on at-risk systems.

Failing water systems are more likely to serve disadvantaged communities. However, some systems have been removed from the failing and at-risk list since the report's data was published. The status of failing water systems is updated daily, while other assessment levels are updated quarterly.

In response to the findings, the water board has proposed plans to distribute approximately $855 million in financial assistance over the next year for projects that address drinking water needs in disadvantaged communities and emerging contaminants.