One-Fifth Of California's Raw Groundwater Is Contaminated

A recent federal report shows that groundwater in California is steeped in contaminants both natural and human-made.

“With the state’s water resources running dry due to California’s unabating drought, a new study by the U.S. Geological Survey (USGS) says that about one-fifth of the raw groundwater contains high levels of contaminants,” KRON recently reported.

Recently published in the journal Environmental Science & Technology, the decade-long survey examined data from 11,000 public-water-supply wells in California. These wells provide water for virtually all residents who consume tap water from public water systems.

“Unlike previous assessments, which focused on contaminants in specific aquifers, the USGS evaluated a range of resources and the population centers affected. The approach could help water providers, regulatory authorities and policymakers relate groundwater quality to health outcomes,” the Los Angeles Times reported, citing a USGS official.

The survey revealed significant contamination of groundwater.

The study “determined that natural contaminants such as arsenic and uranium occur at high concentrations in about 20 percent of the groundwater used for public supply. Human-made contaminants such as nitrate and organic solvents occur at high concentrations in about 5 percent of the resources,” the Times reported.

USGS Groundwater Assessment Chief Kenneth Belitz explained the significance of the findings.

“This is the most comprehensive study of groundwater contamination conducted by any state in the nation,” he said, per the Times. “It tells us which contaminants are most important and where they are.”

“Areas of particular concern, he said, include the Santa Ana Basin and the San Gabriel and San Fernando valleys, where nitrates and organic solvent compounds occur over a relatively large proportion of their groundwater aquifers,” the report said.

What are the policy implications of the study? Briana Mordick, a staff scientists at the Natural Resources Defense Council, said stronger groundwater safeguards are needed.

“Overall, this study shows that for too long California has treated groundwater as out of sight, out of mind,” she said, per the Times. “So, we have a long way to go when it comes to protecting groundwater. Yet, in times of drought, Californians increasingly turn to groundwater supplies.”

For similar stories, visit Water Online’s Source Water Contamination Solutions Center.