There’s a reason the dry Western states are home to adobes that were abandoned 1,000 years ago

Joe McCue thought he had found a desert paradise when he bought one of the new stucco houses sprouting in the granite foothills of Rio Verde, Ariz. There were good schools, mountain views and cactus-spangled hiking trails out the back door.

Then the water got cut off.

Earlier this month, the community’s longtime water supplier, the neighboring city of Scottsdale, turned off the tap for Rio Verde Foothills, blaming a grinding drought that is threatening the future of the West. Scottsdale said it had to focus on conserving water for its own residents, and could no longer sell water to roughly 500 to 700 homes — or around 1,000 people. That meant the unincorporated swath of $500,000 stucco houses, mansions and horse ranches outside Scottsdale’s borders would have to fend for itself and buy water from other suppliers — if homeowners could find them, and afford to pay much higher prices.

Almost overnight, the Rio Verde Foothills turned into a worst-case scenario of a hotter, drier climate, showing what happens when unregulated growth collides with shrinking water supplies.

For residents who put their savings into newly built homes that promised desert sunsets, peace and quiet (but relegated the water situation to the fine print), the turmoil is also deeply personal. The water disruption has unraveled their routines and put their financial futures in doubt.

“Is it just a campground now?” Mr. McCue, 36, asked one recent morning, after he and his father installed gutters and rain barrels for a new drinking-water filtration system.

“We’re really hoping we don’t go dry by summer,” he said. “Then we’ll be in a really bad spot.”

In a scramble to conserve, people are flushing their toilets with rainwater and lugging laundry to friends’ homes. They are eating off paper plates, skipping showers and fretting about whether they have staked their fates on what could become a desiccated ghost suburb.

Some say they know how it might look to outsiders. Yes, they bought homes in the Sonoran desert. But they ask, are they such outliers? Arizona does not want for emerald-green fairways, irrigated lawns or water parks.  At least for now.

And, no, the neighborhood will not become a campground because campgrounds need water.