‘Megadrought’ threatens water and power supplies to millions in US

The “megadrought” gripping the southwestern US has driven water levels at the two largest reservoirs to record lows, forcing unprecedented government intervention to protect water and power supplies across seven states.

Millions of Americans already contending with critical water shortages now face the prospect of black outs as energy demand grows during heatwaves just as hydroelectric power supply is strained. A US power regulator this week warned that a big swath of the US was at risk of blackouts, partly as a result of drought conditions curtailing hydroelectric supplies.

US government climate scientists have said more than half the country is enduring drought conditions, while a separate study estimated that the drought affecting southwestern states was the worst to hit the region for 1,200 years after being exacerbated by human activity.

“This is by far the worst drought in our records,” said Andrew Hoell, a scientist specialising in droughts at the US government’s National Oceanic and Atmospheric Administration (Noaa). “Why would you not care about the worst drought for more than a millennia? We have to live through this.” 

Water levels on Lake Mead, the largest US reservoir, and Lake Powell upstream on the Colorado River have dropped sharply, prompting federal officials to activate an emergency drought plan. Lake Powell’s water levels are at the lowest level since it was filled in the 1960s.

US megadrought map

With Lake Powell threatening to fall below the minimum level required to operate the Glen Canyon Dam, hydropower to an estimated 5.8mn homes across seven states is being threatened.

US officials plan to divert water to Lake Powell from another reservoir upstream in Utah and to release less water than usual downstream to Lake Mead. The actions would “prop up” Lake Powell for an estimated 12 months.

“We’ve never taken this step before in the Colorado River basin,” said Tanya Trujillo, an interior department official, referring to the emergency measures.

Jason Smerdon, a Columbia University climate scientist, described “scary” drought conditions in the south-west states.

“All emissions scenarios suggest increased warming in the south-west and therefore increased drying,” he said. Although the drought could partly be accounted for by natural variability in precipitation patterns, he explained, it was worsened by a long-term trend of aridity caused by human activity.

Noaa’s Hoell, a meteorologist who has tracked extreme weather and it’s relationship to climate change as part of annual studies, said: “The drought we’re having right now has a high likelihood of recurring in the future.”

Bart Miller, a program director at Western Resource Advocates, a climate conservation group, estimated that 14mn Americans relied on the Colorado River for their water, while about 5mn acres of farmland are irrigated using its waters. “More and more people are starting to understand that the path we’re on is a precarious one,” he said.

Nearby states of Nevada, Arizona and California have all stepped up efforts to limit water consumption. Restrictions have been introduced in Nevada’s biggest city Las Vegas, including curbs on the size of golf courses in an effort to reduce the amount of grass that needs to be watered. Farmers in parts of Arizona have also suffered cuts in the water they can use for irrigation.

In California, governor Gavin Newsom launched a $100mn advertising campaign urging water conservation. But when he asked residents in March to cut their water usage by 15 per cent compared with 2020 levels, consumption across the state increased by nearly 20 per cent instead.

Kate Poole, senior director of the water division at the Natural Resources Defense Council, advised further measures to conserve water supplies, including reducing the amounts used in homes and urban areas, encouraging efficient agricultural irrigation and recycling and reusing water.

“We’re facing a future of a lot less water and higher demand because of higher temperatures,” she said.

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