PALM SPRINGS, Calif. — The nation’s largest reservoir has broken a record, declining to the lowest level since it was filled in the 1930s.
Lake Mead reached the all-time low Wednesday night, slipping below a previous record set in June 2015.
The downward march of the reservoir near Las Vegas reflects enormous strains on the over-allocated Colorado River. Its flows have decreased during 16 years of drought, and climate change is adding to the stresses on the river.
As the levels of Lake Mead continue to fall, the odds are increasing for the federal government to declare a shortage in 2018, a step that would trigger cutbacks in the amounts flowing from the reservoir to Arizona and Nevada. With that threshold looming, political pressures are building for California, Arizona and Nevada to reach an agreement to share in the cutbacks to avert an even more severe shortage.
“This problem is not going away and it is likely to get worse, perhaps far worse, as climate change unfolds,” said Brad Udall, a senior water and climate research scientist at Colorado State University. “Unprecedented high temperatures in the basin are causing the flow of the river to decline. The good news is that we have time and the smarts to manage this, if all the states work together.”
He said that will require “making intelligent but difficult changes to how we have managed the river in the past.”
As of Thursday afternoon, the lake’s level stood at an elevation of about 1,074.6 feet. The federal Bureau of Reclamation, which manages the reservoir and Hoover Dam, projects the level to decline a few feet more to an elevation of about 1,071 feet by the end of June, before the level begins to rise again with releases of water from Lake Powell.
Under the federal guidelines that govern reservoir operations, the Interior Department would declare a shortage if Lake Mead’s level is projected to be below 1,075 feet as of the start of the following year. In its most recent projections, the Bureau of Reclamation calculated the odds of a shortage at 10% in 2017, while a higher likelihood — 59% — at the start of 2018.
But those estimates will likely change when the bureau releases a new study in August. Rose Davis, a public affairs officer for the Bureau of Reclamation, said if that study indicates the lake’s level is going to be below the threshold as of Dec. 31, a shortage would be declared for 2017.
That would lead to significant cutbacks for Arizona and Nevada. California, which holds the most privileged rights to water from the Colorado River, would not face reductions until the reservoir hits a lower trigger point.
Representatives of California, Arizona and Nevada said last month that they hope to have a deal by the end of the year in which all three states accept cutbacks earlier than otherwise required in order to head off a more serious crisis.