Western U.S. grapples with water issues amid driest year in a century

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The pallid bathtub ring that marks land dried by the recession of Lake Mead’s water stands as a stark image of a years-long drought in the western United States.

On Monday, U.S. Vice-President Kamala Harris sought to remake the arid icon into a promotional backdrop for the White House, which is advocating a package of infrastructure spending and a “Build back better” bill with money for climate mitigation measures.

“When we look at what’s happening here, we know this is about this lake, but it’s about a region and it’s about our nation,” Ms. Harris said, speaking in front of the reservoir lake, which is now two-thirds empty, as nearby California marked what was by some measures its driest year in a century.

But if the bathtub ring has become a political call to arms, it also testifies to the enormity of the problem confronting a water-starved region of the country, whose greatest difficulties lie not in spending more money, but in attempting to undo a century’s worth of mistaken assumptions and legal handcuffs.

Water in the U.S. is a natural resource whose abundance has been overestimated for a century – and whose shortfalls, exacerbated by climate change, will force major adjustments, scholars say. “Quite a lot of agricultural communities will have to move. People will have to leave,” said Jay Lund, co-director of the Center for Watershed Sciences at UC Davis.

“It’s sort of like a mining town where their ore has been depleted.”

At Lake Mead, at least part of today’s bathtub ring can be traced to a decision made in 1922, when Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming entered the Colorado River Compact to allocate water from the basin. The compact was founded on data that showed 16.5 million acre-feet of available water – a figure based on measurements of three decades that proved to be unusually wet. Over the past 20 years, the Colorado has averaged just 12.4 million acre-feet a year, at a time when usage has averaged 14 million acre-feet. (An acre-foot is enough to cover an acre one foot deep, sufficient for one or two households’ annual needs.)

“Infrastructure is not the solution to our problems. Renegotiating the water allocations is going to be the solution to our problems,” said John Fleck, director of the University of New Mexico’s Water Resources Program.

The difficulty of doing so is rooted in the fundamental importance of water, and the complexities of rules surrounding its use. In some places, senior water rights holders – those with top priority for water – can lose their allocations if they don’t use the water. As a result, even in parched Arizona, some farmers continue to irrigate low-value forage grasses.

Drought levels in the Western U.S.

As of Oct. 12

Exceptional drought

Extreme drought

Severe drought

Moderate drought

Abnormally dry

Wash.

Mont.

Ore.

Idaho

Wyo.

Nev.

Utah

Colo.

Calif.

Ariz.

N.M.

MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE:

U.S. DROUGHT MONITOR

Drought levels in the Western U.S.

As of Oct. 12

Exceptional drought

Extreme drought

Severe drought

Moderate drought

Abnormally dry

Wash.

Mont.

Ore.

Idaho

Wyo.

Nev.

Utah

Colo.

Calif.

Ariz.

N.M.

MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE:

U.S. DROUGHT MONITOR

Drought levels in the Western U.S.

As of Oct. 12

Exceptional drought

Extreme drought

Severe drought

Moderate drought

Abnormally dry

Wash.

Mont.

Ore.

Idaho

Wyo.

Nev.

Utah

Colo.

Calif.

Ariz.

N.M.

MURAT YÜKSELIR / THE GLOBE AND MAIL, SOURCE: U.S. DROUGHT MONITOR

“That requires a lot of water,” said Mojtaba Sadegh, a scholar of climate extremes and risk analysis at Boise State University. “It’s not really reasonable for us to grow water-intensive crops in areas that don’t have water. But it goes back to that water right holder.”

Complicating the picture: Drought conditions have taken place at a time of continued rainfall. The past two decades have seen precipitation continue to meet annual averages in the Sierra Nevada mountains, one of the state’s key water sources.

At the same time, major water users have showed considerable success in cutting volumes.

California’s Imperial Irrigation District, the largest in the Colorado basin, has cut water use by 21 per cent in that time, in part by urban areas paying farmers to save water by using more efficient irrigation or leaving land fallow. State land used for agriculture has shrunk nearly 12 per cent since 2002.

Still, it hasn’t been enough. The water level at Lake Mead has fallen 45 metres in the past 20 years, reaching a level low enough to trigger mandated water cutbacks that will begin in 2022.

Arizona will take the brunt of those reductions. The state says its water supplies from the Colorado River will fall by 18 per cent, although the actual cut will be somewhat less because of previous efforts to conserve water. By 2023, if conditions persist, no Colorado River water will be available for agricultural users of the Central Arizona Project system that uses canals to deliver Colorado waters. Economic activity in those agricultural districts is expected to fall by 60 per cent to 70 per cent, said Ted Cooke, the Project’s general manager.

“It’s going to be painful, it’s going to be more expensive, but this is what we need to do to keep from having even more painful consequences,” he said. Planners have begun to look at expensive alternatives such as desalinization plants or even water pipelines to secure longer-term supplies.

“It’s unlikely that the Colorado is going to somehow magically bounce back to where it has been historically,” Mr. Cooke said.

Rising temperatures at a time of climate change have amplified the problem. Evaporation rates increase in what researchers call a “warm drought.” A paper published earlier this year by a team of university and U.S. government researchers used computer modelling to show that a temperature increase of one degree Celsius would reduce Colorado River flows 6 per cent; a four-degree increase produced a 31-per-cent decrease.

A scientific inability to predict seasonal precipitation means the dry spell could vanish if more plentiful rain resumes.

But scientists and water planners have also warned that worse may yet be coming.

What’s happening today could be merely the opening stages of a megadrought. “We’ve seen in the prehistoric climate records periods of 100 or 200 years where we had very, very dry periods,” Prof. Lund said.

Last week, John Entsminger, general manager of the Las Vegas Valley Water District, warned that “on-the-ground evidence suggests the Colorado River basin is not experiencing drought but aridification – a permanent transition to a drier future.”

Some believe the magnitude of hydrological change should also prompt change in how water is allocated. David Rosenberg, a water scholar at Utah State University, has called for using the amount of water entering Lake Mead as a criterion for how much water is released and consumed. He likened the lake to a bank account: Income is a factor in deciding how much to spend.

“And that’s especially important when the account balance is going down,” he said.

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