Mary Kang and Robert B. Jackson. Salinity of deep groundwater in California: Water quantity, quality, and protection. PNAS, 2016 DOI: 10.1073/pnas.1600400113
Posted: 27 Jun 2016 01:01 PM PDT
New research indicates that California’s Central Valley harbors three times more groundwater than previously estimated, but challenges to using it include pumping costs, ground subsidence and possible contamination from fracking and other oil and gas activities.
California’s drought-stricken Central Valley harbors three times more groundwater than previously estimated, Stanford scientists have found. Accessing this water in an economically feasible way and safeguarding it from possible contamination from oil and gas activities, however, will be challenging. “It’s not often that you find a ‘water windfall,’ but we just did,” said study co-author Robert Jackson, the Michelle and Kevin Douglas Provostial Professor at Stanford. “There’s far more fresh water and usable water than we expected.”
The research, published in the journal Proceedings of the National Academy of Sciences the week of June 27, highlights the need to better characterize and protect deep groundwater aquifers not only in California but in other parched regions as well. “Our findings are relevant to a lot of other places where there are water shortages, including Texas, China and Australia,” said study co-author Mary Kang, a postdoctoral associate at Stanford School of Earth, Energy & Environmental Sciences…. …In the new study, Jackson and Kang used data from 938 oil and gas pools and more than 35,000 oil and gas wells to characterize both shallow and deep groundwater sources in eight California counties. The researchers concluded that when deeper sources of groundwater are factored in, the amount of usable groundwater in the Central Valley increases to 2,700 cubic kilometers — or almost triple the state’s current estimates.
Complications to consider
While this is good news for California, the findings also raise some concerns. First, much of the water is 1,000 to 3,000 feet underground, so pumping it will be more expensive. Without proper studies, tapping these deeper aquifers might also exacerbate the ground subsidence — the gradual sinking of the land — that is already happening throughout the Central Valley. Groundwater pumping from shallow aquifers has already caused some regions to drop by tens of feet. Furthermore, some of the deep aquifer water is also brinier — higher in salt concentration — than shallower water, so desalination or other treatment will be required before it can be used for agriculture or for drinking.
Another concern the Stanford scientists uncovered is that oil and gas drilling activities are occurring directly into as much as 30 percent of the sites where the deep groundwater resources are located. For example, in Kern County, where the core of California’s oil and gas industry is centered near the city of Bakersfield, one in every six cases of oil and gas activities was occurring directly into freshwater aquifers. For useable water — water that the U.S. Environmental Protection Agency deems drinkable if treated — the number was one in three.
….. “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.”