One of the critiques against hydraulic fracturing (or fracking as it is commonly called) is that the process uses millions of gallons of water per well, far too much for arid areas like Dimmit County in Texas.
But how much exactly are millions of gallons? And how much water does fracking use in comparison to other sources of energy and other industries in general?
A back-of-envelope calculation by Jesse Jenkins estimates that fracking only used about 0.3 percent of the total U.S. freshwater consumption in 2011. Assuming that each well consumes about 5 million gallons of water per well on average, this adds up to 135 billion gallons water in that year.
That is far less then the agricultural sector, which consumed more than 32,850 billion gallons of water — about 243 times more. Even golf courses in the U.S. consumed more water with about 0.5 percent of all freshwater.
But judging fracking by totals does not make a lot of sense, given that water use is such a local issue and fracking is one energy source among many.
A 2010 paper by Erik Mielke, Laura Diaz Anadon and Vankatesh Narayanamurti of the Harvard Belfer Center compares the water consumption of the fracking industry to alternative sources of energy — and the result is comparatively positive. According to their estimates, "the consumption of water for the production of shale gas appears to be lower (0.6 to 1.8 gallons/MMBtu) than that for other fossil fuels (1 to 8 gal/MMBtu for coal mining and washing, and 1 to 62 gal/MMBtu for U.S. onshore oil production).
"The increased role of shale gas in the U.S. energy sector could therefore result in reduced water consumption. ... Natural gas-fired combined cycle power plants (CCGT) also have some of the lowest consumption of water per unit of electricity generated, helped by the relatively high thermal efficiency of CCGT plants."
See more in the chart below:
But the authors also point out the possible impacts of the environmental pollution due to the chemicals, which are mixed with the fresh water for the extraction process (read more about this in one of my past articles on the pros and cons of fracking).
And then, of course, the impacts and water consumption vary among different fracking processes and from each location to another.
A new USGS study in Water Resources Research, a journal of the American Geophysical Union, found the amount of water used for hydraulic fracturing across the U.S. ranged from between 2,600 gallons to as much as 9.7 million gallons of water per well. That's a lot of variation.
The study points out that the median volume of water consumption for hydraulic fracturing in horizontal wells increased from about 177,000 gallons per oil and gas well to more than 4 million gallons per oil well and 5.1 million gallons per gas well from 2000 to 2014. However, median water use in vertical and directional wells remained below 671,000 gallons per well.
The USGS study points out that although the number of horizontal wells drilled since 2008 increases, still about 42 percent of new hydraulically fractured oil and gas wells completed in 2014 were either vertical or directional.
Apart from the variation among different fracking processes, the impacts depend on the local water supply. According to report in The New York Times, fracking used about a quarter of the freshwater supply in Dimmit County in 2011. Groundwater withdrawals form the local Carrizo-Wilcox Acquifer used for fracking exceeded one-third of the amount of water recharged in the acquifer by annual precipitation and other factors.
On the other hand, Jenkins estimates that in the more rainy Marcellus shale region of Pennsylvania, Ohio and New York, the water needs for fracking represent only about 17 days of average local rainfall in even the driest month of the year.
As in so many cases, the conclusion is there is no clear conclusion. In comparison to other sources of energy and industries, fracking actually seems to use less water. However, water consumption and its impacts vary from location to location, and among different fracking processes (especially between vertical and horizontal drilling). Also, another issue is the possible water pollution that comes with fracking.
