About a year and a half ago, in the January/February 2017 issue of the magazine, I mentioned predictions from NASA and other organizations that the US is in for a megadrought sometime during this century. A megadrought is one that lasts for decades rather than months or years, and we once believed that they occurred a couple of times each millennium; now, researchers are thinking that warmer temperatures and altered precipitation patterns caused by increased levels of carbon in the atmosphere will make them happen more frequently. The Southwestern states are at greatest risk, followed by the Plains states.

Quoted in a 2016 Atlantic article (https://theatln.tc/2dITRcn), climate researcher Jonathan Overpeck—who coined the word megadrought—calls the phenomenon “devastating as all heck.” The question, he says, is not so much whether one is coming but whether it will be a “warm megadrought”—the kind that has been occurring every few hundred years—or a “searing megadrought,” which he predicts would bring toxic dust storms, kill most of the trees, and make agriculture “all but impossible.” Which type we’re in for depends largely on whether carbon emissions stay the same as they are now or whether we’re able to sharply decrease them.

It’s impossible, of course, to see decades into the future with any certainty, but let’s look at what we can see right now:

As of April, one-third of the continental US was experiencing drought conditions, particularly California and much of the Southwest, but also parts of the central US from Montana and North Dakota down to Texas, and extending as far east as South Carolina and Georgia.

The drought is killing trees. Each state does its own count, but in California an estimated 129 million have died, killed outright by dry conditions or weakened by drought and finished off by beetles or disease. Although they’re dead—along with the flood and heat protection they provided—they’re not gone. The dead wood left behind is potential fuel for wildfires, which will burn hotter and longer than before.

Soil health is suffering. Drier conditions reduce microbial activity in the soil and make it harder for plants to uptake nutrients. This not only reduces crop yields but also prompts some farmers to add more chemical fertilizers to compensate—some portion of which likely runs off and leads to water-quality problems.

Aquifers are drying up. In the last century, the US has pumped about 1,000 cubic kilometers—or two Lake Eries worth—more water from the ground than has been infiltrated. The rate of pumping has accelerated; the US Geological Survey has a map (https://water.usgs.gov/edu/gwdepletion.html) showing where the most water has been taken.

In response to the drought, states that have mandated on-again, off-again restrictions on water use for the last few years are considering making those restrictions permanent; things like hosing down the driveway and letting the hose run while you wash your car would be things of the past. Many people complain about such bans—and go back to their old habits once the perceived crisis is over—but these measures seem pitifully insufficient when held up against the situation in Cape Town, South Africa, where water rationing limits each person to 13 gallons a day, as compared to the 80–100 gallons each of us in the US typically uses.

States are also building or expanding reservoirs, trying to replenish groundwater supplies, and shoring up infrastructure (always a costly proposition) to stop the waste in distribution—anywhere from 10 to 50%. Will these measures be enough to cope during a prolonged drought? What other measures will be needed? How much will we be willing to pay for water, and how far will we be able to transport it if necessary—say, from desalination plants on the coasts to inland cities?