Three Gorges Dam

In brief

On the Yangtze, China's longest river, the Three Gorges Dam is the most powerful hydroelectric plant in the world, with 22.5 GW installed (1 GW = 1 billion watts). It is one of the biggest construction projects ever carried out.

How does it work?

It fulfills three missions at once:

1. Produce electricity: 32 enormous units of 700 MW each, plus two small ones.
2. Protect against floods: before the dam, Yangtze floods caused tens of thousands of victims. The lake can hold back 22 billion cubic meters of flood water.
3. Allow navigation: five locks in a staircase and a boat elevator 113 meters high let 3,000-tonne cargo ships travel up to Chongqing.

Key facts

• Installed power: 22,500 MW, the power of about twenty nuclear reactors of around 1,000 MW each.
• Length: 2,335 m. Height: 185 m.
• Concrete: 28 million cubic meters, poured between 1994 and 2009.

Words to know

• Nuclear reactor: a machine that produces electricity from the energy of uranium.
• Cargo ship: a big ship that carries goods.

Did you know? The lake's water is so heavy (nearly 40 billion tonnes) that, according to NASA calculations, it may have lengthened the day by about 0.06 microsecond (a microsecond is a millionth of a second). Almost nothing, but it is an estimate by NASA!

Going further

Installed power tells what a plant can produce at most at a given moment, a bit like the top speed of a car. The energy produced in a year depends on the water available: a dry year gives less than a wet one. A plant therefore almost never runs at full power all year long.