A single such well can require five million gallons of water, and energy companies are flocking to water auctions, farm ponds, irrigation ditches and municipal fire hydrants to get what they need.
That thirst is helping to drive an explosion of oil production here, but it is also complicating the long and emotional struggle over who drinks and who does not in the arid and fast-growing West. Farmers and environmental activists say they are worried that deep-pocketed energy companies will have purchase on increasingly scarce water supplies as they drill deep new wells that use the technique of hydraulic fracturing.
"It's not a level playing field," said Peter V. Anderson, who grows corn and alfalfa on the parched plains of eastern Colorado. "I don't think in reality that the farmer can compete with the oil and gas companies for that water. Their return is a hell of a lot better than ours."
In average years, farmers and ranchers like Mr. Anderson say they pay about $30 for an acre foot of water — equal to about 326,000 gallons — a price that can rise to $100 when water is scarce. In the spring, during an annual auction of surplus water in northern Colorado, Mr. Anderson and a handful of other farmers were outbid by water haulers who supply hydraulic fracturing wells.