What if the Hoover Dam Broke?

Hoover Dam
The Hoover Dam is an engineering marvel. But if it ever failed, the consequences would be catastrophic. Stephen Simpson/Getty Images

It might be the most impressive U.S. public works projects ever. We're talking about the Hoover Dam. It's located on the Colorado River on the border between Arizona and Nevada. In terms of sheer size, it's massive — standing 726.4 feet (221.4 meters) from foundation to the roadway at the top. That makes it more than 171 feet (52 meters) taller than the Washington Monument.

Shaped like a crescent wedge, the top of the dam is just 45 feet (13 meters) thick, but its base is 660 feet (221 meters) thick — the same distance as the length of two football fields measured end to end. And it's made of sturdy stuff. There is enough concrete in the Hoover Dam (4.5 million cubic yards) to build a two-lane road from Seattle to Miami. It needs every bit of that strength because it holds back 45,000 pounds per square foot of maximum water pressure at the base of the dam.


But have you ever wondered what would happen if the Hoover Dam broke? Granted, it's difficult to imagine what could cause such a break — a massive explosion of some type, a natural disaster of epic proportions or an equally epic human error. But the first thing that would happen is that the reservoir created by the dam, Lake Mead, would be breached.

At full pool, Lake Mead is, by volume, the largest reservoir in the United States. It has enough capacity to hold the entire average annual flow of the Colorado River for two years. As recently as 2016, Lake Mead held up to 9 trillion gallons (34 trillion liters) of water. But with drought conditions in the West, the lake currently holds about 3.5 trillion gallons (13.2 trillion liters) of water. Now, if 3.5 trillion gallons of water were suddenly set loose, it would certainly wreak havoc on everything in its path.


Damage to the Dam

Hoover Dam
Approximately 25 million people depend on water from Lake Mead. They would be devastated if the Hoover Dam were to ever break. Bureau of Reclamation

If catastrophe struck the Hoover Dam and it somehow broke, a catastrophic amount of water from Lake Mead would be released. That water would likely cover an area of 10 million acres (4 million hectares) 1 foot (30 centimeters) deep. To put that area in perspective, the entire state of New Jersey is 9 million acres (3.6 million hectares). Downriver towns and cities would see the most damage, which could include loss of life depending on the amount of warning before the wave. The towns include Laughlin, Nevada; Needles, California; Lake Havasu, Arizona; and even as far south as Yuma, Arizona, and San Luis Rey, Colorado, a border community in Mexico.

There are also three Native American reservations along the Colorado River that would be affected. Some speculate the water would spread into the Mojave National Preserve and communities in southeastern California all the way to the Salton Sea, an area that was routinely flooded by the Colorado River before the dam was built in the 1930s.


Approximately 25 million people depend on water from Lake Mead. The reservoir supplies water for the cities of Las Vegas, Henderson, North Las Vegas and Boulder City, Nevada, as well as municipal and industrial water and irrigation water for downstream users.

The destruction of irrigation water supplies would also have a devastating effect on farming in the region. Farmers in the Imperial Valley get most of their water from the Colorado River, and these irrigation systems would collapse. Prior to irrigation, the Imperial Valley was a barren desert. Today it is home to more than half a million acres of farmland and produces more than a billion dollars in fruits and vegetables every year.

And then there's the electrical grid. Hydropower generation was a major reason for building the Hoover Dam. In fact, it not only financed the project, but income from power generation also continues to pay for the operation, maintenance and replacement work at the dam. According to the U.S. Bureau of Reclamation, Hoover Dam generates on average about 4 billion kilowatt-hours of hydroelectric power, annually, for use in Nevada, Arizona and California. That's enough to serve 1.3 million people.


Frequently Answered Questions

What will happen to Vegas if Lake Mead dries up?
If Lake Mead were to dry up, it would have a devastating effect on the city of Las Vegas. The city gets approximately 90% of its water from the lake, and without it, the city would quickly become uninhabitable.

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