Stanford scientists: ‘Water windfall’ under California’s Central Valley

The good news: According to study co-authors Robert Jackson, Stanford’s Michelle and Kevin Douglas provostial professor, and Mary Kang, postdoctoral associate at Stanford School of Earth, Energy & Environmental Sciences, California’s drought-plagued Central Valley harbors three times more groundwater than previously estimated.

The bad news: Accessing this water in an economically feasible way and protecting it from possible contamination, especially from oil and gas extraction activities, will be challenging.

“It’s not often that you find a ‘water windfall,’ but we just did,” said Jackson who is also a senior fellow at Stanford Woods Institute for the Environment and at the Precourt Institute for Energy. “There’s far more fresh water and usable water than we expected.”

Earlier estimates of California’s groundwater were based on data that are decades old and extended to a maximum depth of only 1,000 feet or less. Until Jackson and Kang’s research was published little was known about the amount and quality of water in deeper aquifers. Their research was published the week of June 27 in the journal Proceedings of the National Academy of Sciences.

“Water a thousand feet down used to be too expensive to use,” said Jackson. “Today it’s used widely. We need to protect all of our good quality water.”

With California now in its fifth year of a seemingly relentless drought, many are frequently turning to groundwater supplies to meet the needs of a thirsty state. This in spite of Gov. Jerry Brown’s 2015 declaration of a drought emergency and mandatory conservation and restrictions.

Using data from 938 oil and gas pools and more than 35,000 oil and gas wells Jackson and Kang were able to identify both shallow and deep groundwater sources in eight California counties. They concluded that the amount of usable groundwater in the Central Valley would increase to 2,700 cubic kilometers — almost tripling the state’s current estimates – when the deeper sources of groundwater are factored in. But getting to it is another matter.

The issue of the newly discovered groundwater is its location. Much of the water is 1,000 to 3,000 feet underground and pumping it to ground level will be costly. Plus, without appropriate environmental studies, ground subsidence – the gradual downward shift or sinking of land – could occur when deeper aquifers are tapped for the water. Subsidence is already happening throughout the Central Valley from groundwater pumping from existing shallow aquifers.

In mid-March, a Los Angeles Times article highlighted subsidence and noted that near the Delta-Mendota Canal the side of a canal had buckled, evidenced by cracked concrete. Nearby a small bridge over another agricultural canal had sunk so much it has to be demolished and replaced with a higher structure, another victim of subsidence. Some 30 miles northeast, near El Nido, CA, the land has been sinking at the staggering rate of a foot a year for the last few years.

The deeper aquifer water is also brinier – higher in concentrated salt – as opposed to more shallow aquifer water. Desalination or other water treatment would be needed prior to agricultural use or for drinking.

Jackson and Kang also expressed concern that as many as 30 percent of the sites where deep groundwater resources are located are also sites for oil and gas drilling activities. In Bakersfield, the site of California’s oil and gas industry core, one in every six oil and gas activity sites was taking place directly into freshwaters aquifers. For water that the U.S. Environmental Protection Agency would deem drinkable, the deep water aquifers versus oil and gas activity was three to one.

But Jackson and Kang were quick to note that water is not necessarily ruined just because a company has hydraulically fractured or used some other chemical treatment near an aquifer.

“What we are saying is that no one is monitoring deep aquifers. No one’s following them through time to see how and if the water quality is changing,” Kang said. “We might need to use this water in a decade, so it’s definitely worth protecting.”

The researchers also noted that their study might also have applications for other dry, parched regions –worldwide – where deep groundwater aquifers may be located.

“Our findings are relevant to a lot of other places where there are water shortages, including Texas, China and Australia,” said Kang.