Fracking may consume more water than previously thought, according to the National Geographic, quoting research by North Dakota's Department of Mineral Resources.

Hydraulic fracturing to extract shale gas and oil may have helped the United States develop its vast shale energy potential and secure its place as a leader on the global shale energy map, but this comes at a price, the magazine said. In one of the states where fracking has become a day-to-day business, authorities have found that, in order for the fuel to flow, "maintenance water" is also required.

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The Bakken Shale in North Dakota is one of the most productive formations in the country. It holds vast reserves of shale energy, reaching trillions of cubic feet of natural gas and billions of barrels of oil. For fracking a well within the formation, companies need to pump about two million gallons of water underground so that the pressure can crack the rocks open and release the gas.

But this is not all. According to new estimates by the North Dakota Department of Mineral Resources, each well requires an average of 600 gallons in maintenance water per day, which prevents salt deposits from building up in the well and blocking the flow of fuel. While this figure seems small it should be looked at in perspective, bearing in mind that there are thousands of fracking wells in the state at the moment. Each of these wells can be active over a period of 30 to 40 years, adding up to a total of 6.6 million to 8.8 million gallons of maintenance water, the department estimated.