Each well that is fracked requires hundreds of thousands or millions of gallons of water, depending on the formation and the depth and length of any horizontal portion of the well. Unlike most industrial uses of water, in which water returns to the water cycle for further use, water used in fracking typically cannot be cleaned up for a broad range of other uses.

Water used in fracking either remains in the well, is “recycled” (used in the fracking of new wells), or is disposed of in deep injection wells, where it is unavailable to recharge aquifers. Thus, fracking takes billions of gallons out of the water supply annually.

In some areas, fracking makes up a significant share of overall water demand. Texas’ Eagle Ford Shale oil play used nearly 18 billion gallons of water in 2013, roughly 16 percent of the area’s total water consumption.

Demand for water by oil and gas companies has harmed farmers and local communities.

For example, the municipal water supply went dry in Barnhart, Texas, in 2013, after excessive water withdrawals for fracking compounded the effects of a years-long drought. Across the Permian Basin, companies have drilled wells and purchased well water drawn from the Edwards-Trinity-Plateau Aquifer, drying up water supplies for residential and agricultural use.

Fracking has used at least 239 billion gallons of water across the nation, according to industry-reported data in FracFocus. Most of that is freshwater from surface or groundwater sources, with only a small share consisting of brackish water or treated and reused water from other frack jobs. The greatest total water consumption occurred in Texas, with half the reported national total.