The ocean is a more promising water source. For centuries people have dreamed of converting saltwater into a limitless supply of fresh water. In 1961 President John F. Kennedy said that “if we could ever competitively, at a cheap rate, get fresh water from saltwater” it would “dwarf any other scientific accomplishments.” By 2008 over 13,000 desalination plants around the world produced billions of gallons of water a day. But “desal,” which is costly and environmentally controversial, has been slow to catch on the United States.

Recycled sewage offers an interesting, if aesthetically questionable, drinking source. (Supporters call recycled sewage “showers to flowers”; detractors condemn “toilet to tap” schemes.) Plans for sewage recycling, which involves extracting and purifying the water, are slowly gaining acceptance. Windhoek, Namibia — one of the driest places on earth — relies solely on treated wastewater for its drinking supply. El Paso releases some of its recycled sewage into the local aquifer, where it eventually mixes with groundwater and, after a time, is pumped and treated for use as drinking water. Fairfax, Va., gets 5 percent of its tap water from recycling effluent. But the “yuck factor” has led to a sharp debate about its merits.

MEANWHILE, global demand for water is expected to increase by two-thirds by 2025, and the United Nations fears a “looming water crisis.” To forestall a drought emergency, we must redefine how we think of water, value it, and use it.

Singapore provides a noteworthy model: no country uses water more sparingly. In the 1950s, it faced water rationing, but it began to build a world-class water system in the 1960s. Now 40 percent of its water comes from Malaysia, while a remarkable 25 to 30 percent is provided by desalination and the recycling of wastewater; the rest is drawn from sources that include large-scale rainwater collection. Demand is curbed by high water taxes and efficient technologies, and Singaporeans are constantly exhorted to conserve every drop. Most important, the nation’s water is managed by a sophisticated, well-financed, politically autonomous water authority. As a result, Singapore’s per-capita water use fell to 154 liters, about 41 gallons, a day in 2011, from 165 liters, about 44 gallons, in 2003.

America is a much larger and more complex nation. But Singapore’s example suggests we could do a far better job of educating our citizens about conservation. And we could take other basic steps: install smart meters to find out how much water we use, and identify leaks (which drain off more than 1 trillion gallons a year); use tiered water pricing to encourage efficiency; promote rainwater harvesting and wastewater recycling on a large scale. And like Singapore, we could streamline our Byzantine water governance system and create a new federal water office — a water czar or an interagency national water board — to manage the nation’s supply in a holistic way.

No question this will be an expensive, politically cumbersome effort. But as reports from New Mexico, Texas, Louisiana, Georgia and Florida make plain, business as usual is not a real option. The python of drought is already wrapped tightly around us, and in weeks — and years — to come it will squeeze us dangerously dry.