Less than eight months after Hurricane Harvey pelted the Texas Gulf Coast with torrential rainfall, drought has returned to Texas and other parts of the West, Southwest and Southeast, again forcing state governments to reckon with how to keep the water flowing.

Nearly a third of the continental U.S. is in drought, more than three times the coverage of a year ago. And the specter of a drought-ridden summer has focused renewed urgency on conservation efforts, some of which would fundamentally alter Americans’ behavior in how they use water.

In California, for example, officials are considering rules to permanently ban water-wasting actions such as hosing off sidewalks and driveways, washing a vehicle with a hose that doesn’t have a shut-off valve, and irrigating ornamental turf on public street medians.

In Amarillo, Texas, the water department stresses conservation with the message “every drop counts,” and urges customers to do “at least one thing a day to save water.” Oklahoma City has a similar mantra.

Years of studies by government and environmental groups have warned that future demand for water is threatening to outstrip availability unless policymakers take steps to reverse those trends. “More and more cities around the world are running into limits on how much water they have available to meet their needs,” said Peter Gleick, co-founder of the Pacific Institute.

To understand the potential dangers, U.S. officials could look to parched Cape Town, South Africa. The city of 4 million spent months struggling to fend off Day Zero, when it was projected to become the first major urban center to run out of water. Residents skimped on dishwashing and laundry, took minishowers and washed their hands with sanitizer. The objective: to cut individual water consumption to 50 liters a day, or 13.2 gallons, far below the U.S. average of 80 to 100 gallons. Hundreds queued up for daily water rations as law enforcement officers enforced restrictions.

U.S. government and environmental experts generally agree that no major city is in imminent danger. But residents in some small communities have struggled, and U.S. experts worry that protracted global warming, worsening droughts, vanishing groundwater and growing populations will make Americans increasingly vulnerable. One critical water resource threatened is the Colorado River System, which includes parts of seven states and provides water for as many as 40 million people. Lake Mead, which serves 25 million people, is less than half full.

Burgeoning population growth and a decadeslong decline in groundwater resources — which supply half of the nation’s residents and nearly all of its rural population — is adding to the U.S. water insecurity, the U.S. Geological Survey said. “Basically, we are pumping groundwater faster than it recharges,” said Breton Bruce, a scientist with USGS in Denver.

Most of the states on the front lines have spent decades shoring up their defenses, operating on a proven regimen that the next drought is lurking not far in the future. But the search for effective water policy also has been fraught with conflict, often displaying the competing interests of agriculture, property owners, big cities, small communities, energy developers, conservationists and environmentalists and a host of others. Solutions never come easy.

“Water is fundamental to all the interests,” said Luke Metzger, executive director of Environment Texas, “and, at times of scarcity, it can be a feeding frenzy, where all the interests are competing for a finite supply.”