Many shale-gas operations are in arid areas or in areas of high water stress, including the US, China, Mexico and South Africa. There is increasing concern about the amount of water used during hydraulic fracturing (fracking) and whether water constraints could limit shale-gas production.

Researchers from the University of Texas at Austin, US, conducted an in-depth evaluation of water demand versus supply in the semi-arid Texas Eagle Ford play, the largest shale-oil producer worldwide. They concluded that, with appropriate management, water availability should not limit future shale-energy production.

"While there have been many studies about methane production and contamination resulting from hydraulic fracturing, few studies focus on the amount of water used," said Bridget Scanlon, who published the findings in Environmental Research Letters (ERL). "Many of the past studies have not had access to commercial databases, but we have. We also conducted interviews with oil and gas companies."

Scanlon and colleagues found that water demand for hydraulic fracturing in the Eagle Ford play – 82-billion litres in 2013 – represents 16% of consumptive water use in the region. "The dominant water user in the region is irrigation, accounting for 62–65% of water consumption," Scanlon told environmentalresearchweb. "This is followed by municipal (10–12%) and steam electric power (7–13%)."

The researchers project that the maximum fracking water use across the next 20 years will be 1.5-trillion litres from 62,000 additional wells, representing approximately eight times the fracking water use to date. "We have not been fracking for long, so we only have five years of data on which to base our calculations," said Scanlon. "But we also have to remember that fracking is a temporary phenomenon – while demand for fracking water is currently increasing, after 20–30 years this demand will be gone."

Irrigation, on the other hand, has been demanding water for more than a century. Scanlon and colleagues calculated that projected fracking water use represents roughly 10% of historic groundwater depletion resulting from irrigation during the last century in the surrounding Winter Garden region.

But Scanlon does have concerns about declining water levels in the region. "Even after only five years of fracking, we have seen water levels in some wells show a large decline," she said. "While water-level declines are small in much of the region, large declines (mostly 30–60 m) were estimated to extend across roughly 6% of the western part of the region. These monitored water-level declines are generally coincident with high density of fracking wells."

Brackish groundwater may provide a viable alternative to freshwater, the researchers believe, with projected fracking water use representing 0.4% of the estimated 360-trillion litres of brackish groundwater storage.

Previous research estimated that around 20% of water used for fracking was brackish. But consumption of brackish water has increased considerably since then – some operators indicate that 60–80% of their water use is brackish. Many operators report drilling into deeper units to access brackish water and avoid competing with domestic wells for shallow groundwater. Some districts are even incentivizing the use of brackish water: the Pecan Valley Groundwater Conservation District recently revised its regulations to allow up to 20 times more groundwater pumpage if brackish water is withdrawn from the aquifer.

"While our research has shown that there is plenty of water available for fracking, it is important that academics work with industry to better understand and manage water resources," said Scanlon. "It is companies that hold most of the data, and I hope that industry is willing to continue to collaborate with researchers to improve water-resource management."

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