Because of its reliance on freshwater supplies, fracking has considerable impact on local water resources, yet the details of those impacts remain murky. To provide some clarity, a recent report thoroughly examined water consumption and other related impacts associated with horizontally drilled, hydraulically fractured shale-gas wells. Requiring about 5 million gallons of fluid (mostly water) per well, it's clear that the water intensity of shale gas is more significant than previously thought and likely compels more diligent oversight of the oil and gas industry and its water use. Such oversight becomes even more important as increasingly large volumes of wastewater are produced from growing shale-gas development, which has the potential to swamp disposal capacity and heighten pollution concerns.
The study, prepared for the environmental nonprofit Earthworks, gathered and analyzed publicly available data provided by the oil and gas industry to state agencies in Pennsylvania (from 2009 to 2011 ) and in West Virginia (from 2010 to 2012). Though data in these Marcellus Shale states offered a fuller assessment of water-related impacts, researchers were hindered by spotty industry reporting and incomplete datasets.
Despite these hindrances, the study found:
- The water footprint per unit of energy (i.e., gallons of water per thousand cubic feet [Mcf] of natural gas) is higher than previously reported: West Virginia--1.6 to 2.2 gallons per Mcf; Pennsylvania--3.2 to 4.2 gallons per Mcf (over three times greater than earlier estimates that range from 0.7 to 1.2 [Subscription only link]).
- The amount of fluid injection per well averages (injection fluid overwhelmingly comprised of freshwater): West Virginia--5 million gallons; Pennsylvania--4.3 million gallons.
- The average volume of injected fluid that flows back to the surface is much lower than previously estimated with over 90 percent of injected fluid remaining underground and lost to the water cycle: West Virginia--6 percent flowback; Pennsylvania--8 percent flowback.
- The amount of waste water is rapidly growing with the number of new wells. Pennsylvania generated 70 percent more waste - or 613 million gallons - between 2010 to 2011.
- There is a closely interlinked shale-gas waste disposal system between Pennsylvania, West Virginia and Ohio. Although wastewater is increasingly being reused, Ohio has large volumes of wastewater injected into deep disposal wells, wells that have been linked to micro-earthquakes throughout the US. (Data trends show a decline in the use of specialized wastewater treatment plants, especially in Pennsylvania, because treated water discharged to receiving water bodies has been found to contain unsafe amounts of heavy metals, salts and even low level radioactive materials.)
Any research that seeks to account for total water use in shale-gas extraction must take a cumulative approach that tabulates each stage of the multipart process, which the authors enumerate and explain. Such a methodology must account for both water consumed in fracking itself and water consumed to treat and dispose of hazardous wastewater. This provides a more comprehensive and sensitive understanding of the water consumed during the entirety of shale-gas extraction, both in terms of water quantity (withdrawals) and water quality (pollution).
The method used to determine the water footprint is what distinguishes this study from earlier shale-gas water impact studies. The authors for the first time used the concepts of blue and grey water footprints contained within the Water Footprint Assessment methodology developed by the Water Footprint Network. Blue water footprints represent the volume of surface and groundwater used during the production of a product (in this case, natural gas). Grey water footprints represent the volume of freshwater needed to dilute pollutants to maintain water quality. This methodology combined with gas production averages and actual reported data gave "a sense for the scope of water contamination versus water use," explains coauthor Dr. Dustin Mulvaney, professor of Sustainable Energy Resources at San Jose State University, in an email correspondence. "Similar approaches to the blue water footprint have been used (though not by name), but the grey water footprint had never been applied," he continues. Thus earlier studies that omitted water pollution costs (grey WF) and focused solely on the water used (blue WF) have likely underrepresented the impact that shale-gas extraction has on water resources.
If shale-gas production increases rapidly enough in the Marcellus Shale, despite the increase in water use efficiency and wastewater recycling, the sheer volume of wastewater could potentially become problematic. As Mulvaney observes:
You can expect that there will be a need to increase disposal capacity so long as there is such rapid regional growth in natural gas. This may have been what has happened. The disposal capabilities may already have been overwhelmed if falling prices for natural gas did not slow efforts to get it out of the ground. If there are excess volumes then there will have to be an increase in disposal capability somewhere.
The research team, which includes Evan Hansen, principal, and Meghan Betcher, environmental scientist, both of the environmental consulting firm, Downstream Strategies, notes that their "findings suggest that the volumes of water used to fracture Marcellus Shale gas wells are quite substantial, the quantities of waste generated are significant, and continual improvement and enforcement of data collection and reporting requirements will be necessary to minimize the potential impacts to water resources in West Virginia, Pennsylvania, and Ohio."
Although outside the scope of this report, wastewater concerns also exist in New York, which is under a statewide fracking moratorium.
This study is groundbreaking, not only because it quantifies the larger-than-reported water footprint for shale-gas wells, but also because it advances the Water Footprint Assessment methodology. An accurate accounting of the water intensity of shale-gas and shale-oil extraction allows society to understand and confront the freshwater tradeoffs among others for public health and the environment, which are at the center of fossil fuel exploitation. By not hiding behind the numbers, we can make clear-eyed decisions about the future of US energy, health and the environment.
Webinar with the authors: Reporting from the Fracking Front (Switzer Foundation Webinar Series)