Fallout: What Would Happen if the Hoover Dam Broke?

If disaster struck and the Hoover Dam stopped functioning, 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 major cities would see the most damage, in the event of the dam's physical collapse. Water flows would engulf many towns and growing cities around Mohave county, including Laughlin, Nevada; Needles, California; Lake Havasu, Arizona; and even as far south as Yuma, Arizona, and San Luis Rey, Colorado. Without any advanced warning about the physical breach, Lake Mead's water levels could result in significant losses of life.

There are also three Native American reservations along the Colorado River that would be affected if the dam's walls collapsed. 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 users on the downstream side.

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 basin, 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 hydroelectric 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 produces on average about 4 billion kilowatt-hours of hydroelectric power, annually, for use in Nevada, Arizona and California. That's enough to cover the electricity needs of 1.3 million people.