“We’re not going to be able to raise the food we need,” said Ben Rainbolt, executive director of the Rocky Mountain Farmers Union. “How are we going to produce this with less?”

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. Although Mr. Anderson ultimately got the water he needed as bids settled after the auction, the mere shadow of energy producers at the auction offered a glimpse of their growing presence in the rush for Western water.

“Energy companies are moving quickly to shore up supplies,” said Reagan Waskom, director of the Colorado Water Institute at Colorado State University. “They’re going to find it, and they’re going to pay what they need to pay, and it’s on an order of magnitude of what crop producers can afford to pay. That changes the whole deal.”

Oil and gas companies estimate that they will use about 6.5 billion gallons of water in Colorado this year, and that figure makes up only 0.1 percent of overall water use, according to state data. Their consumption represents more water than is used making snow on the ski slopes or greening the state’s golf courses. But it is paltry compared with the deluge needed for irrigation and agriculture, which accounts for 85.5 percent of Colorado’s water use.

Still, the industry is growing fast. The Colorado Oil and Gas Commission estimates that the state’s oil and gas water needs will grow by 16 percent over the next three years.

“Water flows uphill to money,” said Mike Chiropolos, a lawyer for Western Resource Advocates, an environmental group based in Boulder. “It’s only going to get more precious and more scarce.”

In June, the group released a study that accused Colorado of underestimating the amount of water used in hydraulic fracturing, also known as fracking, saying the true figure was between 7.2 billion and 13 billion gallons per year — enough to serve as many as 296,100 people.