Colorado River reservoir sees water shortage for first time

NEW YORK • With climate change and long-term drought continuing to take a toll on the Colorado River, the US federal government has for the first time declared a water shortage at Lake Mead, one of the river's main reservoirs.

Monday's declaration triggers cuts in water supply that, for now, will mostly affect Arizona farmers. Beginning next year, they will be cut off from much of the water they have relied on for decades.

Much smaller reductions are mandated for Nevada and for Mexico across the southern border.

But larger cuts, affecting far more of the 40 million people in America's West that rely on the river for at least part of their water supply, are likely in coming years as a warming climate continues to reduce how much water flows into the Colorado River from rain and melting snow.

"As this inexorable-seeming decline in the supply continues, the shortages that we're beginning to see implemented are only going to increase," said Ms Jennifer Pitt, who directs the Colorado River programme at the National Audubon Society.

The Bureau of Reclamation, an agency of the Department of the Interior, declared the shortage as it issued its latest outlook for the river for the next 24 months.

That forecast showed that by the end of this year, Lake Mead, the huge reservoir near Las Vegas, would reach 325m above sea level. It has not seen a level that low since it began to fill after the completion of Hoover Dam in the 1930s. The lake will be at 34 per cent of capacity.

Water levels at Lake Mead and the other large Colorado reservoir, Lake Powell, in Utah, have been falling for years, leaving a telltale white "bathtub ring" of mineral deposits along the shoreline as demand has outpaced supply.

The mandatory water supply cuts are part of a contingency plan approved in 2019 after lengthy negotiations among the seven states that use Colorado River water: California, Nevada and Arizona in the lower basin, and New Mexico, Utah, Colorado and Wyoming in the upper basin.

The shortage announced on Monday so far affects only the lower basin states, but a similar shortage may be declared for the upper basin as early as next year.

The current cuts will reduce Arizona's supply of Colorado River water by about 20 per cent.

In anticipation, some farmers have fallowed fields or switched to less water-intensive crops. Others will be pumping more groundwater to make up for the cuts, which raises additional questions about sustainability because groundwater supplies are not unlimited.

This year has been one of the worst ever for run-off into the Colorado River, said Mr Ted Cooke, general manager of the Central Arizona Project, a system that delivers the river water to Arizona.

"The big question is, what's going to happen in 2022?" he said. After two decades of drought, "one thing that we don't have is the resiliency in the reservoirs, because they're so low".

Dr Kevin Moran of the Environmental Defence Fund said a new US infrastructure Bill, which has passed the Senate but faces a rocky road in the House, includes several billion dollars that could help the region cope with this new reality.

This includes money to improve so-called natural infrastructure, including forests, watersheds and underground aquifers, which could help bolster the supply, or at least slow the decline.

"Our water infrastructure is not just man-made reservoirs and treatment plants," he said. "It's the natural system, too."

NYTIMES