Bureau of Reclamation Lower Colorado Region Banner
Reclamation Home             Regional Offices             Newsroom             Library             Projects & Facilities

What is the biggest dam in the world?

Photo. View of Hoover Dam from downstream.When Hoover Dam was finished in 1935 it was the tallest dam in the world. From about 1938 until 1948 the Hoover Dam powerplant was the largest hydroelectric plant in the world. Since then, larger facilities have been built, and people often ask, "What is the biggest dam in the world today?" The answer depends on what you mean by biggest. Do you mean the tallest dam? Or do you mean the one with the most material in it? Or, how about the biggest hydroelectric producer? The answer to each of these questions is a different dam.

World's Largest Dam by Volume

Syncrude Tailings Dam in Canada is currently ranked number one by volume of construction material at 706,320,000 cubic yards (540,000,000 cubic meters). These are mine tailings, so as mining operations continue, more tailings will be added and the structure will grow larger. In contrast, Hoover Dam contains 3,250,000 cubic yards (2,600,000 cubic meters) of concrete, which is much less. Hoover Dam is solid concrete and it was designed specifically to be used as a dam, whereas the Syncrude Tailings is the piled up dirt left over from mining operations. Although the material is compacted and otherwise treated to make a stable structure, it relies on volume of material to hold back water. Hoover Dam relies not only on volume of material, but the strength of that material as well.

World's Tallest Dam

Currently, the tallest dam in the world is Nurek Dam on the Vakhsh River in Tajikistan. It is 984 feet (300 meters) tall. Hoover Dam is 726.4 feet (221.3 meters) tall. Today, Hoover Dam still ranks in the top 20 of the tallest dams in the world, but only in the concrete gravity and arch categories. Many other rock and earthfill dams have surpassed Hoover in height. There is one dam in the United States taller than Hoover Dam, and that is the Oroville Dam on the Feather River in California. It stands 770 feet (235 meters) tall, but it is an earthfill dam, not a concrete structure like Hoover.

World's Largest Hydroelectric Plants

The Sanxia (or Three Gorges) Dam on Yangtze River in China has an installed powerplant capacity of 22,500 megawatts (MW), but ranks 2nd in the world in hydropower generation. Its output of 84 billion kilowatt-hours (KWh) per year is still surpassed by Itaipu Dam on the border between Brazil and Paraguay. Itaipu's plant has a capacity of 12,600 MW, and has produced 90 billion KWh in a single year. The largest hydroelectric plant in the United States is at Grand Coulee Dam. Its three powerplants have a capacity of 6,809 MW, and it generates, on average, about 21 billion KWh, while Hoover Dam's powerplant has a capacity of 2,074 MW and generates approximately 4 billion KWh a year.

(Sources: International Commission on Large Dams and United States Society on Dams)

Last Reviewed: 6/25/2012