“We don’t respond really well to, ‘O.K., the government says you’ve got to do this, and by God you’re going to do it or we’re going to string you up,’ ” Mr. Perry said.

So far, the 10 percent cutback has been working, he said. But Mr. Grant of the water district said systemwide usage in March, just before individual cities introduced restrictions, was the highest for that month in five years.

For Permian Basin cities, the water crunch presents hard choices — and perhaps especially so for Midland, which will lose about half of its reservoir rights when a contract with the water district ends in 2029.

Besides what the district supplies, Midland owns a groundwater well field called T-Bar Ranch, which contains enough water to last the city several decades. But developing it would cost about $140 million and take five years or more, Mr. Purvis said.

Other groundwater is more readily available via a lease that Midland has on land managed by the University of Texas System. But without a desalination plant, it must be diluted with lake water to reduce fluoride. Also, Mr. Purvis said, oil companies use water on the same lands, and their water-intensive drilling technique, hydraulic fracturing, could capture a significant part of the reserves. In isolated places around the region, leaks from old oil wells also affect the groundwater, water officials say.

“No one anticipated that we would be in this kind of a drought,” Mr. Perry said, explaining why Midland had not prepared better, adding that he thought the city would have enough water for the long term.

Clayton Williams, a Midland businessman and former Republican candidate for governor, hopes to sell water from his ranch near Fort Stockton to Midland customers, 90 miles away. A hearing next month in Fort Stockton, where this has stirred controversy because some officials want to keep the water in their area, may clarify the plan’s future.