The Western mega-drought | The week

California and the Southwest are facing high temperatures, severe drought, and a new hotter and drier normal. Here’s all you need to know:

What is the current situation ?
The West is in the midst of a generalized drought emergency of historic intensity. Seventy-two percent of the West is in “severe” drought conditions, according to the US Drought Monitor, and more than 25 percent is in “exceptional” drought, the most extreme category. Many reservoirs are at record levels; Last month, Lake Mead, which provides water to 25 million people, hit its lowest level since filling in the 1930s. The mountain snowpack, which typically feeds reservoirs during the dry months by cast iron, is almost non-existent. And while it’s not even summer yet, a record-breaking heat wave baked through the already parched region last week, sending temperatures up to 107 in Salt Lake, 116 in Las Vegas and 118 in Phoenix. The current drought “is set to become the worst we’ve seen in at least 1,200 years,” said Kathleen Johnson, a paleoclimatologist at the University of California at Irvine.

What is behind the conditions?
The immediate cause is the record precipitation over the past year combined with above-average temperatures. In Arizona, California, New Mexico, and Nevada, the past year has been the driest on record since record keeping began in 1895; in Utah, it is the second driest. The high heat intensifies the drought; In turn, this worsens the heat as the soil moisture, which normally reduces evaporative heat, decreases. Droughts in this region are cyclical, but experts agree that climate change is making this one – which has already been going on for 20 years – far more serious. In a study published last year in the journal Science, the researchers determined that climate change worsened drought conditions by 46% between 2000 and 2018. We “live in a new climate,” said Stanford University climatologist Noah Diffenbaugh, “in which these Water deficits result mainly from the influence of temperature warming. “

What are the consequences?
Farmers without water cannot grow their crops. “We are looking at an absolutely catastrophic year,” said Ryan Jacobsen of the Fresno County Farm Bureau. In New Mexico, large tracts of farmland are being decommissioned at the request of state officials; in California, up to a million acres of farmland could go unused this year, at an economic cost of billions. Many of the 2 million Californians who depend on well water may not find groundwater to tap into. Power generation from dams has plummeted, and a hydroelectric power station in California’s Lake Oroville faced a possible shutdown due to falling water levels last week, even as scorching temperatures strained the city. electrical network. Perhaps most worryingly, powder magazine conditions threaten a cataclysmic wildfire season that could even overtake that of last year. All of these conditions are deeply worrying for this summer, but they are part of a larger trend that could cause trouble for the future of the region.

What is the general trend?
Scientists suspect the Southwest is in the throes of a “mega-drought” – a severe drought that lasts for decades. In a study published last year, scientists who analyzed ancient tree rings identified four such mega-droughts in the past 1,200 years, and said the current one may be the worst of them. And climate change can keep this drought locked in. Many scientists now speak of “aridification” instead of drought, to indicate a permanent condition instead of a transient problem – a new normal. To make matters worse, the mega-drought comes at a time when the population of the Southwest is booming. Arizona, Nevada, Texas and Utah are all among the fastest growing states in the country. “We’ve always been dry, but we didn’t have all of these people,” said Ed Bowler of St. George, Utah, where the population has almost sevenfold since 1980.

What can be done?
Communities are going to have to adapt to a new, hotter and drier reality, which means making tough choices. The region needs to “dramatically increase our conservation and rethink how we use almost every gallon of water,” said John Entsminger, chief executive of the Southern Nevada Water Authority. There may need to be fewer farms in the southwest, with water rights “shifted from agricultural to urban use,” said Michelle Baker, a Utah State University environmentalist. Water-intensive grass and bush landscaping will have to give way to less thirsty native plantings, dictated by laws like Nevada’s new ban on “decorative sod.” States will need to figure out how to live with smaller water allocations from the Colorado River, which serves 40 million people in seven states. Some experts are optimistic about the region’s ability to adapt, but others are less optimistic, pointing out that climate change will only accelerate. “It’s just going to get hotter,” said Brad Udall, a climatologist at Colorado State University. “You haven’t seen anything yet.”

The overexploited Colorado River
As the southwest grills in temperatures over 100 degrees, the Colorado River offers both a marker of the intensity of the drought and a harbinger of future battles over dwindling water supplies. . Seven states are drawing from the river as part of a plan drawn up in 1922. But from the start, that plan allocated more water than the river actually supplied, and this scarcity worsened as the flow of the river river has shrunk by 20% while the population drinking from it has exploded. Reservoirs fed by the Lake Powell and Lake Mead rivers, which together provide water to 40 million people, are both about 35 percent full. In 2019, the states struck a deal, the Colorado River Drought Contingency Plan, which triggers mandatory water cuts once Lake Mead drops to a certain point, as is expected to happen this summer. But it expires in 2026, and states will have to strike a new deal that will include painful cuts to their water allocations. This will require tense negotiations between competing interests, including cities, developers, farmers, environmentalists and indigenous tribes. “This is the new baseline,” said Eric Kuhn, former general manager of the Colorado River District. “There is no more water in the system.”

This article first appeared in the latest issue of The week magazine. If you want to read more, you can try six risk-free issues of the magazine. here.


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