Hi all…an open access paper published today in PNAS reports that studies of deep groundwater indicate “that California’s Central Valley alone has close to three times the volume of fresh groundwater and four times the volume of underground sources of drinking water (USDWs) than previous estimates suggest.” Great news, but they then point out that “Up to 19% and 35% of oil/gas activities have occurred directly in freshwater zones and USDWs, respectively, in the eight counties. Deeper activities, such as wastewater injection, may also pose a potential threat to groundwater, especially USDWs.”
The oil industry’s position that they typically extract water from, and discharge into, deep aquifers which aren’t used for drinking water may need to be reconsidered by the industry and regulators where water shortages are projected and the feasibility of deep extraction becomes more attractive (or even necessary).
Bill
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Salinity of deep groundwater in California: Water quantity, quality, and protection
Mary Kanga and Robert B. Jackson
http://www.pnas.org/content/early/2016/06/21/1600400113.full.pdf
http://www.pnas.org/content/pnas/early/2016/06/21/1600400113.abstract.html?collection
Abstract
“Deep groundwater aquifers are poorly characterized but could yield important sources of water in California and elsewhere. Deep aquifers have been developed for oil and gas extraction, and this activity has created both valuable data and risks to groundwater quality. Assessing groundwater quantity and quality requires baseline data and a monitoring framework for evaluating impacts. We analyze 938 chemical, geological, and depth data points from 360 oil/gas fields across eight counties in California and depth data from 34,392 oil and gas wells. By expanding previous groundwater volume estimates from depths of 305 m to 3,000 m in California’s Central Valley, an important agricultural region with growing groundwater demands, fresh [<3,000 ppm total dissolved solids (TDS)] groundwater volume is almost tripled to 2,700 km3, most of it found shallower than 1,000 m. The 3,000-m depth zone also provides 3,900 km3 of fresh and saline water, not previously estimated, that can be categorized as underground sources of drinking water (USDWs; <10,000 ppm TDS). Up to 19% and 35% of oil/gas activities have occurred directly in freshwater zones and USDWs, respectively, in the eight counties. Deeper activities, such as wastewater injection, may also pose a potential threat to groundwater, especially USDWs. Our findings indicate that California’s Central Valley alone has close to three times the volume of fresh groundwater and four times the volume of USDWs than previous estimates suggest. Therefore, efforts to monitor and protect deeper, saline groundwater resources are needed in California and beyond.”
