So far in parts one and two of the this series of posts on the safety of hydraulic fracturing, we have looked at both the overall risk to surface and ground water from unconventional oil and gas activities, as well as the potential for the wells, which allow oil and gas to come to the surface, to fail.

A final potential concern regarding hydraulic fracturing and water is the amount of water used to fracture a well. While the numbers may sound large, in terms of how much water it takes to fracture a well, in the grand scheme of things the percentages of total water use are quite small.

This is highlighted in a recent study conducted by researchers at Duke University that attempted to estimate just how much water was being used by hydraulic fracturing in the United States.

Beginning with how much water it takes to fracture a well, the study found that this can vary widely depending on the field and whether you’re hydraulically fracturing for oil or gas. Specifically, it was found that water use ranged from 13.7 to 23.8 million litres per well for shale gas and 1.3 to 15.1 million litres per well for unconventional oil. That’s a considerable amount of water.

Those large volumes translate to an annual estimated water use for combined shale gas and unconventional oil of 183 billion litres, between 2012 and 2014.  But to put this into perspective, this amounts to 0.87 per cent of total industrial water use and 0.04 per cent of total fresh water use in the United States per year.

Recycling of water is also improving. Prior to 2011, only 13 per cent of waste water was recycled in the Marcellus, but by 2011 that number had risen to 56 per cent and more recently, in some circumstances, waste water recycling is approaching 90 per cent.

One thing the above estimates of water use don’t take into consideration is comparisons of water use with other forms of energy. As seen in the table below from our recent study, unconventional natural gas extraction, processing and its eventual use in electricity production is far less water intensive than other forms of energy. Specifically, the water use intensities for the extraction and processing of unconventional natural gas are approximately two times smaller than those for coal, three times smaller than those for nuclear, and 933 times smaller than the water use intensity of irrigated corn ethanol.

It’s true that hydraulic fracturing uses large volumes of water, but when put into context those numbers don’t seem so big. In the end water use for fracking is only a small percentage of water use in the U.S., and the natural gas which fracking unlocks has the benefits of using less water than other forms of energy used in electricity generation.