What happens if Lake Powell runs out of water?
If Lake Powell recedes much further, one of the nation’s largest reservoirs could be at risk of no longer generating hydropower for the region.
The lake was just under 24 percent full as of last week, and had lost 16 feet in the last year. Its depth level currently stands at around 3,530 feet.
How much power does the lake generate?
Northern Arizona’s Glen Canyon Dam, which creates the lake, has a full capacity of 1,320 megawatts, according to the U.S. Bureau of Reclamation. However, the receding water levels have already greatly reduced the reservoir’s generating capacity, to about 800 megawatts—about 60 percent.
How many people rely on it?
Lake Powell generates power for about 5.8 million households and businesses in Arizona, Colorado, Nebraska, Nevada, New Mexico, Utah and Wyoming.
In addition to the power the lake generates directly, it is a major source of grid resilience when full, serving as a quick backup source in cases where solar or wind power can’t meet demand.
The loss of generation from the lake would deprive the grid of about a quarter million households’ worth of power.
On top of the hydropower the lake generates, it’s the source of drinking water for the 7,500 residents of Page, Az., and the 1,443 members of the LeChee chapter of the Navajo Nation.
If allocations from the Colorado River dip below the levels necessary for some customers to receive hydropower, “the real question [becomes] what can our grid accommodate from a hydropower perspective in terms of compensating production losses from Glen Canyon?” said Justin Mankin, an assistant professor of geography at Dartmouth College.
“In the abstract, people seem to think that hydropower can be compensated from other sources, [but] in practical terms, no one really seems to have that figured out,” said Mankin, who co-wrote the National Oceanic and Atmospheric Administration’s Drought Task Force’s annual report in 2021.
What’s the point of no return?
“It’s important to differentiate between Lake Powell running dry versus Lake Powell dropping below elevation 3,490 [feet],” Taylor Hawes, Colorado River program director at the Nature Conservancy, told The Hill in an interview.
Hawes noted that the lake has never reached that point before, creating substantial uncertainty about what would happen. “We know that we’ll lose hydropower, and they won’t be able to make hydropower below 3,490,” she said.
Complicating matters are the ongoing talks on allocation between the seven states on the Colorado River, the source of the lake’s waters.
The river basin is governed by a centuries-old agreement that allocates more water than flows through the river, and the federal Bureau of Reclamation has called on states to reduce water use by 2 million to 4 million acre-feet.
What happens if we pass that point, and what can be done?
Officials have already taken some stopgap measures to avert the lake getting down to the pivotal 3,490-foot mark.
Earlier this year, the Bureau of Reclamation released about 500,000 acre-feet from Flaming Gorge Reservoir in Utah and Wyoming to Lake Powell, increasing its elevation about 16 feet. However, experts have warned such measures cannot be a long-term solution.
In addition, Mankin said, interventions like the Flaming Gorge release treat the western U.S.’s 20-year drought as a localized phenomenon rather than a regional one.
“The idea that these smaller upstream reservoirs can continue to compensate Powell’s losses, that’s not the case,” he said. “Powell is not drying out in a vacuum.”
If the lake’s levels drop below 3,490, Hawes added, the Bureau of Reclamation will have to run water through a series of river outlet tubes, the lowest delivery mechanism in the lake, for the first time since the 1980s, and bureau officials “don’t actually know if they can handle that much water,” she said.
If the outlet tubes can’t meet the reservoir’s needs, she said, the flow of water in the Grand Canyon itself could be reduced to a trickle.
The Glen Canyon Institute has advocated for draining Lake Powell, both to replenish Lake Mead and to restore Glen Canyon, which was flooded to create Lake Powell. Institute Executive Director Eric Balken said taking such a step would better position stakeholders to address the drought on their own terms rather than simply running out.
If the water level continues falling on its own, “below minimum power pool, the dam is physically incapable of releasing a lot of water. And so this creates a lot of potential problems downstream in the Grand Canyon, it creates management problems for the reservoir itself in Glen Canyon, and most importantly, it jeopardizes the upper [Colorado River] basin’s ability to meet its delivery obligation downstream,” Balken said.
“If it’s done intentionally, the drawbacks of losing the reservoir could be minimized and the benefits could be maximized,” Balken told The Hill. “If decision makers do nothing and take no action and just let the reservoir crash without structurally modifying the dam, there will be a lot of really big problems.”
Ultimately, experts said the future of the lake must be addressed in a way that creates the certainty it was intended to provide.
Lake Powell “is supposed to buffer water supply during times of drought [and] it is not performing that function now. It is not creating certainty in the water market,” Mankin said.
On the contrary, he said, “it’s actually become this locus of huge uncertainty, which doesn’t allow downstream users to make effective plans, because they don’t know what their allocations are going to be. And it doesn’t allow ratepayers who rely on power production from the canyon to be forward-thinking and operate under conditions of certainty.”
“Cities, farmers and fish all need certainty when it comes to water, and this is the opposite of certainty,” Hawes said. “This is very unpredictable and these are going to be difficult conversations in the coming years.”