Decades Of Drought

by Dish Staff

Drought Map

The Southwest faces a surprisingly high risk of it:

A new study published as a joint effort by scientists at Cornell University, the University of Arizona, and the U.S. Geological Survey finds that the chances of the Southwest facing a “megadrought” are much higher than previously suspected. According to the new study, “the chances of the southwestern United States experiencing a decade-long drought is at least 50 percent, and the chances of a ‘megadrought’ – one that lasts up to 35 years – ranges from 20 to 50 percent over the next century.”  …  [Columbia climate scientist Richard] Seager says that the region hasn’t had a megadrought in several centuries; the Dust Bowl drought of The Grapes of Wrath, though incredibly severe, was not long enough to qualify.

Scott K. Johnson offers a sense of scale:

In the 1150s, for example, reconstructions tell us that the Southwest was in the midst of almost 25 years of below-average precipitation. For a solid decade, the Colorado River averaged about 85 percent of its normal flow. Arizona is allocated about 15 percent of the Colorado’s water, which now rarely makes it to the Gulf of California before drying up. That’s a decade without an Arizona’s share of water.

Bioclimatologist Park Williams, speaking with Doyle Rice, notes that more of the West has been in a state of drought over the past 15 years than in any other 15-year period since the 1150s era. Rice zooms in on California, which – while not as vulnerable to megadroughts as Arizona or New Mexico – has recently seen “the state’s worst consecutive three years for precipitation in 119 years of records”:

As of Aug. 28, 100 percent of the state of California was considered to be in a drought, according to the U.S. Drought Monitor. More than 58 percent is in “exceptional” drought, the worst level. Record warmth has fueled the drought as the state sees its hottest year since records began in 1895, the National Climatic Data Center reports. Because of the dryness, Calif. Gov. Jerry Brown declared a statewide drought emergency this year. Since then, reservoir storage levels have continued to drop, and as of late August, they were down to about 59 percent of the historical average. Regulations restricting outdoor water use were put in place in late July for the entire state. … There are reports of wells running dry in central California.

Tom Philpott gulps:

This (paradoxically) chilling assessment comes on the heels of another study (study; my summary), this one released in early August by University of California-Irvine and NASA researchers, on the Colorado River, the lifeblood of a vast chunk of the Southwest. As many as 40 million people rely on the Colorado for drinking water, including residents of Las Vegas, Los Angeles, Phoenix, Tucson, and San Diego. … The researchers analyzed satellite measurements of the Earth’s mass and found that the region’s aquifers had undergone a much-larger-than-expected drawdown over the past decade – the region’s farms and municipalities responded to drought-reduced flows from the Colorado River by dropping wells and tapping almost 53 million acre-feet of underground water between December 2004 and November 2013 – equal to about 1.5 full Lake Meads drained off in just nine years, a rate the study’s lead researcher, Jay Famiglietti, calls “alarming.”

Considering how much of the Colorado River Basin, which encompasses swaths of Utah, Colorado, California, Arizona, and New Mexico, are desert, it’s probably not wise to rapidly drain aquifers, since there’s little prospect that they’ll refill anytime soon. And when you consider that that the region faces high odds of a coming megadrought, the results are even more frightening.

Meanwhile, B. Lynn Ingram, coauthor of The West Without Waterwarns of “cautionary parallels between our modern society and past societies that were forced into mass migration and in some cases collapsed under prolonged periods of drought”:

A particularly dry stretch occurred between 900 and 1400 AD, during the so-called Medieval Climate Anomaly, when two 100-year long droughts descended on the West. These droughts caused large lakes to shrink or dry out completely, more frequent wildfires, and extreme hardship for native populations as natural water sources shrank and other resources declined.  … Like these past societies, our modern society experienced rapid population growth throughout the relatively wet 20th century. Today, California has 38 million people, a number that may double by 2050, made possible by developing all available sources of water, including underground aquifers that took thousands of years to accumulate. We are not only using all available surface waters, we are drawing down our “water in the bank.” The drilling of these aquifers is currently unmonitored and unregulated, providing free water Central Valley farmers, increasingly only to those who are willing and able to drill deeper and deeper wells. Over the past year, the companies that install these wells and pumps are working round the clock, often deepening wells by 1,000 to 2,000 feet.

(Map from the U.S. National Drought Monitor)