USGS finds vast reserves of salty water underground in California

A new nationwide study has unearthed the huge hidden potential of tapping into salty aquifers as a way to relieve the growing pressure on freshwater supplies across the United States.

Digging into data from the country’s 60 major aquifers, the U.S. Geological Survey reports that the amount of brackish — or slightly salty — groundwater is more than 35 times the amount of fresh groundwater used in the United States each year.

Supplies exist in every state except New Hampshire and Rhode Island, with the largest reserves in the central U.S. In the Golden State, the California Coastal Basin and Central Valley aquifers together contain close to 7 billion acre-feet of brackish water, which if desalinated could provide enough water for the state’s needs for the next 160 years.

Untreated brackish water can replace fresh water for some uses, but would have to be desalinated for municipal use. A recent study by the Oakland-based Pacific Institute found that the costs of doing that were competitive with other methods of adding water capacity.


“This is a big leap for the water sector,” said Newsha Ajami, director of urban water policy at Stanford University’s Water in the West program. “It’s amazing we have so much capacity now to map and measure.”

Finding evidence of more than 800 times the amount of brackish groundwater the U.S. currently uses, the study provides a starting point for more in-depth local analyses.

“The use of brackish groundwater has been growing since the 1970s,” said Jennifer Stanton, a USGS hydrologist and lead author of the study. “Our goal was to determine the data gaps so we know enough about the resource to use it sustainably.”

Brackish water contains dissolved minerals ranging from 1,000 to 10,000 milligrams per liter. But the salinity doesn’t matter too much for the mining and oil and gas industries, which have been the biggest users of untreated brackish groundwater. The salty cousin of fresh water also finds favor with many livestock species that can drink brackish water in the lower concentration range, as well as with carefully managed salt-tolerant crops. When it comes to using brackish water for municipal use, however, the U.S. Environmental Protection Agency follows higher standards that entail treatments to remove salts.

Texas, California and Florida lead the pack with the most number of brackish groundwater desalination plants.

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