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Introduction to What if the Hoover Dam broke?

The Hoover dam is one of those miracles of the modern world that almost defy explanation. When you stand next to it, the size is unbelievable. It is more than 700 feet high (imagine a 70-story building). The top of the dam is more than 1,200 feet long. At the base, it is an amazing 660 feet thick and at the top it is 45 feet thick. The water on the lake side is more than 500 feet deep, and the lake holds a total of 10 trillion or so gallons of water -- enough water to cover a state like Connecticut 10 feet deep.

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Let's say the Hoover dam broke. This is difficult to imagine, given its thickness. No conventional bomb would have an effect on a dam like this. It is difficult to imagine even a nuclear bomb having an effect, unless it were an extremely powerful one and it were inside the dam at the time of explosion. But let's say that some sort of tremendous earthquake or an asteroid strike or some other natural disaster were to somehow eliminate the Hoover dam in one fell swoop. What would happen?

The first thing that would happen is that 10 trillion gallons of water would move as quickly as it could out of the lake and down the river in a huge tsunami of water. The Hoover dam is located in a desert area that is not hugely inhabited below the dam, but there are still some sizeable populations. Lake Havasu City, population 40,000, is about the biggest town in the United States along the river. Bullhead city, population 30,000 is also close to the dam. Needles, California; Blythe, California; and Laughlin, Nevada all have populations of around 10,000 people as well.

Where the water would do immense damage is in the lakes below Hoover dam. It turns out that below Hoover dam is another large lake called Lake Mohave, which is held in place by Davis dam, and below that is Lake Havasu, held in place by Parker dam. These are smaller lakes and smaller dams. For example, Lake Havasu only holds about 200 billion gallons of water.

Hoover Dam releasing outflow after a test.

Photo courtesy U.S. Bureau of Reclamation

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Damage to the Dam

As the water released by the Hoover Dam moved through these two lakes, it would likely destroy them and their dams as well. That's where the real impact would be felt, because these lakes affect a huge number of people. The water in them produces hydroelectric power, irrigates farmland and supplies drinking water to cities like Los Angeles, Las Vegas, Phoenix and San Diego.

The Hoover dam produces roughly 2,000 megawatts of power. Davis and Parker dams produce less, but together they might all produce 3,000 megawatts. That represents about one half of one percent of the total electrical power produced in the United States. If you eliminated a sizable amount of generating capacity like that, especially in that area of the country (near Los Angeles and Las Vegas, for example), it would definitely cause problems.

The destruction of irrigation water supplies would also have a huge 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 the home of more than half a million acres of farmland and produces more than a billion dollars in fruits and vegetables every year.

There would be large effects as well from the loss of drinking water. For example, Las Vegas gets 85 percent of its drinking water from Lake Mead -- the lake behind Hoover dam. With the loss of water and the loss of power, Las Vegas would become uninhabitable, and that would displace 1.5 million residents and empty more than 120,000 hotels rooms and the casinos, bringing the multi-billion-dollar gambling industry in this city to a halt.

Isn't it amazing how much commerce, and how many people, depend on that one dam?