This article appeared in the January/February 2022 issue of Discover magazine as "All-Time Dry." Become a subscriber for unlimited access to our archive.
Just halfway through the summer of 2021, a startling record was set: By one measure, almost 100 percent of the Western U.S. was in drought. In 122 years of observation, never had that much land been that dry west of the Continental Divide.
Lack of precipitation was a factor. But even more significant were high temperatures. In June alone, 202 all-time record highs were set in the West. For the Southwest, these extremes amplified a 20-year megadrought that’s been drying out the region and, most notably, the Colorado River Basin.
In the effort to meet rising water demands in the basin, the two largest reservoirs in the U.S. — lakes Mead and Powell along the Colorado River — both shriveled to historic lows this summer. “It’s a ticking time bomb,” says Brad Udall, a water and climate research scientist at Colorado State University.
The drying up, or aridification, of the Southwest has been taking a toll on the snowmelt-dependent Colorado River for many years. As a result, its natural flows have diminished by nearly 20 percent since 2000. Meanwhile, demand for its water — the lifeblood of an economy exceeding $1.4 trillion — has only increased, with roughly 40 million people counting on it today.
On Aug. 16, the U.S. Bureau of Reclamation issued the first-ever shortage declaration for Lake Mead. This will trigger substantial cuts in 2022 to water deliveries, especially to agricultural users, in Arizona, Nevada and Mexico. Arizona will take the biggest cut, totaling about a fifth of its Colorado River supply. Residents in cities like Phoenix, the fastest growing in the U.S., will be spared. But farmers who irrigate crops with water from the Central Arizona Project canal will see their supplies reduced by about 30 percent.
Bigger cuts that would hit cities, not just farmers, may be coming. “With growing populations and continued development in the metro areas of Las Vegas, Phoenix, and L.A., it’s very concerning how water resource issues will impact these urban areas in the not-so-distant future,” says David Simeral, a climate scientist with the Desert Research Institute.
Researchers caution that, for the Southwest in particular, including parts of the Colorado River Basin, the prolonged heat could signal a new, more-arid norm beyond temporary droughts.
A 2020 study published in Science showed that the period between 2000 and 2018 was the driest since the late 1500s. And, notably, about 46 percent of the severity of this current megadrought could be attributed to human-caused climate change. “This appears to be just the beginning of a more extreme trend toward megadrought as global warming continues,” the study authors cautioned.