Still, even the region’s residential suburbs are among the state’s biggest water users, with mega-mansions that can drain more than 1,000 gallons a day on average. Critics say a flurry of reservoir building in the region decades ago created a perception of cheap, unlimited water that drove wasteful habits — a myth that is unraveling in the face of extreme drought, aging infrastructure and exponential population growth.

North Texas’ water demands are currently about 600 billion gallons a year and is expected to almost double by 2060, but so far the search for new sources has come up short. The billionaire T. Boone Pickens’s plan to sell water to Dallas from the Texas Panhandle fizzled, and he found customers elsewhere. (Mr. Pickens is a major donor to the Tribune.)

Concerns over wildlife habitats derailed plans for a massive reservoir in East Texas. Most recently, the United States Supreme Court struck down North Texas’ effort to buy water from Oklahoma reservoirs after that state resisted. The next big idea — the proposed $3.4 billion Marvin Nichols Reservoir — has met fierce opposition from environmentalists and rural communitiesin northeast Texas who say that 70,000 acres would be lost to the reservoir, including farms, forest and wildlife habitat.

All this has left critics asking: Will the region finally get serious about conserving water, or will it simply build its way out of the problem?

Local officials say that both are required, and that they are trying to strike the right balance.“You’ll never eliminate the need for a major water supply for the Metroplex,” said David Marshall, the engineering services director for the Tarrant Regional Water District, a wholesale supplier to dozens of North Texas entities including the City of Fort Worth. But through conservation, he said, “we’ll definitely delay it. The conservation has really exceeded my expectations.”

As with the rest of the state, North Texas has focused its conservation efforts on landscaping, the use of big-budget advertising campaigns, and replacement programs for water-using appliances and lawn-watering equipment. The results are notable: the Tarrant district says its customers have saved 72.3 billion gallons since 2007, which would support five years of population growth.

Dallas and Fort Worth say their homes and businesses use about 10 percent less water than they did a decade ago.