What Happens if Lake Mead Hits Dead Pool and Hoover Dam Stops Working?

The Hoover Dam, standing 726.4 feet tall, is one of the greatest feats of American engineering—and one of its most important. The dam formed Lake Mead, the largest man-made reservoir in the U.S., which irrigates 1.5 million acres of land and provides water to 40 million people—a vital source of life to the populations of California and Nevada.

But what would happen if it were to break—and how likely is that? As the water levels of both Lake Mead, and its tributary the Colorado River, are near record lows after a yearslong megadrought in the region, the chances are slim.

Robert Glennon, a water policy and law expert and emeritus professor at the University of Arizona, told Newsweek: "It's not too likely to break because there's not much water. Usually dams break when the river overtops the dam and water flows, and the downstream base erodes the dam itself.

"The question [as to whether it will break] is a great one, but I would reframe it. What's more likely to happen is that the water in Lake Mead hits what we call dead pool. Dead pool is when the water above the dam is so low that no water passes through it."

Hoover Dam
A photo shows the Hoover Dam, which forms Lake Mead in Nevada. superjoseph/Getty

If dead pool were reached, it would be a catastrophe. Much of life in the southwest U.S. exists as we know it due to the Hoover Dam—and dead pool would cause all its operations to cease.

Before the Hoover Dam's construction, the southwest used to be at the mercy of the wild Colorado River, which would occasionally overflow and flood farmlands. The Hoover Dam allowed the water to be controlled, so that this would no longer happen.

The Hoover Dam was also constructed to provide a reliable source of water for the southwest, including major cities like Los Angeles.

It also produces hydropower. The Hoover Dam produces around 4 billion kilowatt-hours of hydroelectric power each year for Nevada, Arizona, and California, for around 1.3 million people.

If the Hoover Dam stopped functioning, the electrical grid would be majorly affected. The income the electricity produces also funds its upkeep. The dam is completely self-supporting, meaning if it broke, income for repairs would be difficult to come by.

"[Dead pool] would mean no hydropower, no water supply. So there are 40 million people who rely on the Colorado River and if there's no water coming through Hoover Dam that affects the water supply for 40 million people. And we're talking about the Great Western cities, southwestern cities. We're talking about farmers and we're talking about tribes," Glennon said.

"A final way to look at this problem, if you live in New York City, why should you care about the flow in the Colorado River? And the answer is, do you like to eat salad? Most Americans do. And between November and March, more than 90 percent of the salad greens to leafy lettuces comes from this region. So if there's no water flowing down the river there's no salad."

But how likely is this scenario?

A physical breach is extremely unlikely. It would take a natural disaster or a huge explosion to collapse the dam. But if this were to happen, the water held in Lake Mead would spill out over the land as the walls collapsed.

When the lake is at its maximum capacity of 1,220 feet, it holds 9.3 trillion gallons of water. This is enough water to cover 10 million acres, which is bigger than the state of Maryland.

Lake Mead's water levels are not what they once were, but they remain large. It holds enough water to cause a wave that would devastate communities.

It is difficult to predict how many places would be damaged, as it all depends on the speed at which the wave comes. But the wave from Lake Mead would likely wash away or destroy anything in its path.

Anthony F. Arrigo, associate professor of communication at the University of Massachusetts Dartmouth and author of the 2014 book Imaging Hoover Dam: The Making of a Cultural Icon, told Newsweek: "Without the dam system along the Colorado it's not hyperbole to say that the southwest would be virtually uninhabitable. The reason that the southwest exists as we know it today is because of the dams. There is no other reason.

"There simply is not enough water falling from the skies or under people's feet to support the millions of inhabitants and hectares of agriculture. The only reason that Los Angeles was able to grow beyond a few hundred thousand people is because they received lots of water piped in from the Colorado River."

While its physical collapse is not likely, dead pool is—and officials believe it could happen in just a few years.

As of February 15, Lake Mead's water levels were at 1047.58 feet. This is only around 30 percent of its full capacity. In July 2022, the lake's water levels reached an all-time low of 1,040 feet.

Lake Mead's water levels could reach 992 feet by the end of July 2024, the U.S. Bureau of Reclamation reported in a two-year "probabilistic projection" for the Colorado River system. This is the "probable minimum" level the lake could reach within 24 months.

Officials have warned that dead pool could be reached by 2025, if the lake continues drying up at the rate it is currently. But Glennon said that one would need a "crystal ball" to know for sure.

"The longer we wait, the worse it will get and there's a specific reason for this. The Grand Canyons in the west are V-shaped, like a martini glass. So they're very wide at the top and very narrow at the bottom.

"We're now getting close to the bottom. And in each foot of elevation at the narrow section of the canyon, holds less water. So we can drop a heck of a lot faster than the feet way up higher.

"It would be a catastrophe for the cities and farmers and tribes downstream. A catastrophe for the food production in the four months of the calendar from November to March. Dead pool, the killing of the Colorado River, is just a horrible thought."

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