Amid punishing drought, federal water managers projected Tuesday that — by a very narrow margin— the crucial Lake Mead reservoir on the Colorado River won't have enough water to make full deliveries to Nevada and Arizona in 2018.
A federal report shows the surface level of the lake behind Hoover Dam is expected to remain high enough this year to avoid a shortage declaration in 2017. But it'll still be a mere 4 feet above a 1,075-foot elevation action point.
For 2018, the U.S. Bureau of Reclamation projects the lake level could fall short — by less than 1 foot.
That would trigger cuts in water deliveries that an official said would most affect Arizona farmers.
Chuck Cullom, Colorado River programs chief for the Central Arizona Project, said cities and tribes wouldn't immediately be affected.
But his agency, based in Phoenix, would enact plans to drain underground storage supplies and cut irrigation allocations by half.
"It's good to know we won't be in shortage in 2017," Cullom said. "We're hopeful we can again avoid shortage in 2018."
Las Vegas, which draws 90 percent of its water from Lake Mead, might not feel much effect of a shortage declaration because conservation and reuse programs have in recent years cut the amount of water the area consumes by about 25 percent, Southern Nevada Water Authority spokesman Bronson Mack said.
Still, conservationists said such a close call should be a wake-up to water-users.
"The good news is that we missed the trigger level. The bad news is that we missed it so narrowly and we remain dangerously close to automatic cuts," said Nicole Gonzalez Patterson, Arizona director of the organization Protect the Flows.
"This is the loudest of wake-up signals for the region's water managers," she said.
Bart Miller, of Western Resource Advocates, called for stepped-up water conservation, reuse and management programs.
Public water managers in Nevada, California and Arizona said they've been working together for years to avoid a shortage declaration.
They cite swaps and storage programs that have propped up the lake level, by at least temporarily reducing the amount of water drawn for use elsewhere.
John Entsminger, head of the Southern Nevada Water Authority, pointed to one program that lets water agencies in Las Vegas, Los Angeles, Denver and Phoenix pay water rights holders to conserve and reduce their water use.
Bureau of Reclamation spokeswoman Rose Davis said part of the reason that the lake level will be 4 feet above shortage this year is because agencies been working since 2014 to keep water in it.
"The partners have all been tested and no one's had it easy," she said. "But they're keeping to their agreements and continuing to talk."
At stake is life itself for about 40 million residents in the arid Southwest, plus millions of acres of farms, businesses and tribal entities in seven states. Mexico is also promised a share of river water.
A 1922 interstate agreement allocates to states a combined 15 million acre-feet of water. An acre-foot is about enough to serve two homes for a year.
Resource managers say population growth and steady drought have cut the amount the river takes in from rainfall and snowmelt annually, making the river oversubscribed.
A shortage declaration would cut 11.4 percent of Arizona's promised 2.8 million acre-feet, and 4.3 percent of Nevada's allotted 300,000 acre-feet. The amount of water at stake would, combined, serve more than 625,000 homes.
Even if a shortage is declared, drought-stricken California will be able to draw its full 4.4 million acre-foot allocation of Colorado River water.
Advocates with the Great Basin Water Network in Salt Lake City and the Denver-based group Save the Colorado blamed the 16-year drop in water levels at Lake Mead on rise in demand as much as a drop in supply.
"We use more water than the Colorado provides in even an average year," said water network spokesman Howard Watts III. "That fact has caused the decline of Lake Mead just as much as the drought."
Gary Wockner, of Save the Colorado, pointed to plans by people in mountain states plans to dam and divert water before it reaches the desert.
"We need to save the river, not further drain it," he said.
William Hasencamp, Colorado River resources chief for the Metropolitan Water District of Southern California, said he thinks that in the end a shortage declaration is inevitable.
"It's not 'if,' but 'when,'" said Hasencamp, whose agency serves nearly 19 million customers from Los Angeles to San Diego. "The fact that we're not in shortage now is a testament to what we've been doing."