Newly Identified Deep Groundwater in California

In a new article, “Salinity of deep groundwater in California: Water quantity, quality, and protection,” Stanford researchers, Robert Jackson and Mary Kang used data from 938 oil and gas pools and more than 35,000 oil and gas wells to characterize and estimate both shallow and deep groundwater sources in eight California counties. The article was published in the journal Proceedings of the National Academy of Sciences in the June 27th issue and for the first time tried to use newer data to examine the groundwater within deeper aquifers.

from Jackson and Kang

Previous estimates of groundwater in California are based on data that are decades old and only estimated groundwater resources down a few hundred feet, though Californians have begun tapping the groundwater down below 1,000 feet below grade. The utilization of the deeper aquifer is unknown because the State Water Resources Control Board Groundwater Ambient Monitoring and Assessment Program does not have or make available the well depth data for the 200,000 wells it has water quality data for. Until now, little was known about the amount and quality of water within deeper aquifers. Drs. Jackson and Kang 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, triple the state’s current estimates.

While this is good news for California, the findings do not solve California’s water problems. First, much of the water is 1,000 - 3,000 feet or deeper below grade, so pumping it will be more expensive. Without proper management, tapping these deeper aquifers might also exacerbate the subsidence, the sinking of the land, that is has been happening throughout the Central Valley. Groundwater pumping from shallow aquifers has already caused some regions to drop by more than 75 feet. Secondly, groundwater salinity increases with depth and some of the deep aquifer water is as expected, higher in salt concentration than shallower groundwater, so desalination or other treatment will be necessary before it can be used for either drinking or irrigation for agriculture in the state.

The scientists used data from oil and gas production provided by the California Department of Conservation, Division of Oil, Gas, and Geothermal Resources (DOGGR) that contained information on formation water salinity and total dissolved solids, TDS, from oil and gas pools and records of wells drilled to depths of a several thousand meters. A concern that the Stanford scientists point out is that oil and gas drilling activities are occurring directly into as much as 30 % of the sites where the deep groundwater resources are located. In Kern County near Bakersfield where much of California’s oil and gas industry is centered, one of every six oil and gas wells was drilled directly into freshwater aquifers. For potentially useable water, water that the U.S. Environmental Protection Agency deems drinkable if treated, the number was one in three.

As Dr. Jackson points out in the linked video, the oil and gas industry is the only industry that is allowed to inject chemicals directly into potential drinking water sources. The more we learn about the fate of these chemicals, the greater the concern. With California in its fifth year of drought and the growing need for water in California, we need to reconsider these practices. We need to better characterize and protect deep groundwater aquifers not only in California but in other parched regions where these water resources will be needed before too long.