Few have done as well as Mike Ames, who says he's had a hand in about two-thirds of the 70-plus depots. Ames, a burly man with a broad nose, grew up across the border in Montana and began selling irrigation equipment in Williston, northwest North Dakota's largest town, in the 1980s. Seven years ago, Ames opened his first depot, selling water for 35 cents a barrel -- equal to 42 gallons -- to farmers for mixing with pesticides. Then came oil. "I was in the right place at the right time," he says. Today, he charges 60 cents a barrel. He's also hired 20 people in the past year to look after the dozen depots he runs -- he owns three and operates the rest for other farmers.

He says he and the other water providers are helping wean the country off imported oil; thanks in part to the Bakken, U.S. oil production is rising consistently for the first time in over 25 years.

But private sellers face growing competition. Oil and oil-field services companies are applying for their own permits as they settle into the state. One Texas-based company, Select Energy, acquired permits to draw nearly 6 billion gallons annually from Lake Sakakawea, a giant reservoir on the Missouri.

The other new competitor is public. Because quality drinking water is scarce in western North Dakota, the state has worked for decades to build pipelines to deliver river water to residents. A system in the southwest, begun in 1977, still isn't complete; projects in the northwest have not materialized. Pushed to the limits of their existing water supplies by oil-driven population growth, the area's towns recently established the Western Area Water Supply Authority to build their own project. To lower the construction time to just a few years, they're borrowing $110 million from the state -- and plan to ask for another $40 million -- to be paid back by selling water to oil companies. They already have four depots running, with plans for eight more.

From the air, the need for water-supply projects is clear. Amid the prairie hills, new developments sprawl everywhere: water depots and drilling rigs like playing pieces in an elaborate game, a yard full of drill pipe here, a field full of campers there, new motels.

In Watford City, the largest town in McKenzie County, the population leapt from 1,744 in 2010 to an estimated 6,500 today, and city officials are planning for 15,000 over the next decade. Just behind Water Supply Authority Executive Director Jaret Wirtz's office, a local trucking company has cut several acres out of the surrounding prairie to build housing for 1,000 people. "Everybody wants to do 500 homes here, 300 homes there," Wirtz says. "Well, those all take water."

The drillers may soon be able to get more water from Lake Sakakawea, relieving some stress on groundwater. The Army Corps of Engineers opened the lake to oil-field use this spring after determining there would be little environmental effect, though it could be a year before planned projects are complete. In written comments, the Environmental Protection Agency said the Corps presented limited evidence to support its conclusion, failed to examine the impacts of withdrawals on downstream areas and as a result, "may not fully recognize potential direct, indirect, or cumulative impacts."

The Missouri River -- the country's longest -- supplies drinking water to 3 million people, irrigates 550,000 acres and cools 25 power plants. The utilities want more water released from dams for increased power production. Downstream states want more for barge traffic. Meanwhile, back in the oil fields, one utility has begun building two 45-megawatt natural gas plants that will require up to 75 gallons per minute. Fargo, North Dakota's biggest city, is still pushing for completion of a Sisyphean engineering feat begun in the 1950s to reroute water from the Missouri across the state to supplement its water supply. "Eventually, that river is going to get tied up," Wirtz says.

Lee and LaShell Tjelde live near the Montana border, where the land begins to undulate, exposing bare hillsides of striped earth. Lee is tall and strong, with a red face and wire-rimmed glasses. His family has ranched here for three generations.

On a drive through the couple's pastures, he points out stock dams nearly dry in mid-May. When they run out, Tjelde pumps groundwater for his cattle. He holds one permit to irrigate from the same groundwater, and he applied for a second nearly two years ago. Such requests once took months to process, but since drilling began, the Water Commission has been overwhelmed. The aquifer here is among those showing signs of stress, and hydrologist Alan Wanek says he will be cautious about issuing new permits. Even as the Tjeldes and several neighbors wait, five other neighbors have temporarily converted existing irrigation permits to sell to the drillers. "To my eyes," Tjelde says, "that's just not right."

Water is already hard to find. When the Tjeldes built their home, they drilled fruitlessly and eventually resorted to a "water witch," who divined a narrow seam of water in the ground. The well only pumps about four gallons per minute, and it's too salty for the garden. So LaShell collects rainwater in two 500-gallon barrels, one of which is nearly empty. Some neighbors must haul water from town. "If these aquifers are dried up through industrial use, what's left for us?" Lee says. "This is our life out here."