Hydraulic fracturing, or fracking for short, is widely touted as the key to unlocking vast reserves of oil and natural gas trapped in underground shale formations. The problem is that the “hydro” is in short supply.

Peter Zeihan is an analyst with Austin-based private intelligence firm Stratfor.

“This is a very water intensive process. You don’t get a particularly high percentage of the water back even if you’re being very conservative with its use. This has really delayed developments in, for example, the Eagle Ford Shale.”

Fracking a single well in south Texas’ Eagle Ford shale takes up to thirteen million gallons of water, due to the formation’s unusual geology. But even the more forgiving Barnett Shale near Fort Worth demands at least three million gallons for each new well.