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Building the world's biggest dam



What does it take to build the world’s largest hydroelectric dam? If China’s Three Gorges is any indication, the answer is around 90 years and £16.8 billion.

3 Gorges

The Three Gorges dam is the largest ever built. The dam body was completed in 2006 and is so big that it’s been said a shift in its total water mass can literally slow the rotation of the Earth.

The original idea to build a massive dam over the Yantze River can be traced back to former leader of China, Sun Yat-sen in 1919, who stated that a dam built downstream of Three Gorges could be capable of generating 30 million horsepower (22GW). Proposals were regularly put forward in the decades ahead, with Mao Zedong supporting the project and even writing a poem about it in 1956. However it wasn’t until 1992 that the project was finally approved, with construction commencing on December 14th 1994.

Even with the far more modern construction techniques available than back in Sun Yat-sen’s day, construction was still a mammoth task that took 12 years. In the process, 463,000 tonnes of steel was used - enough to construct 63 Eiffel Towers, and 27,200,000m3 of concrete while 102,600,000m3 of earth was moved. 

Finally in 2006 the body of the dam was completed. 

The massive straight-crested concrete gravity structure is the largest dam in the world. 2,335m (7,661 ft) long, it sits between steep canyons with the highest point sitting 185m (607ft) above sea level. 

The dam fundamentally transformed the surrounding area, creating a reservoir that can hold up to 39.3 billion cubic metres of water, submerging large areas of the Qutang, Wu and Xiling gorges for 600km upstream. 

In addition to the dam’s use as a power station, the creation of this reservoir allows ocean freighters to navigate 2,250km inland from Shanghai on the East China Sea to the inland city of Chongqing. A ship lift was installed on the dam that can elevate ships of up to 3,000 tons vertically 113m (371ft). A helical gear system is used to climb or descend a toothed rack, which takes just 20 minutes to lift a ship. 


The primary purpose of the dam is to generate power using 34 hydroelectric generators, each with a capacity of 700MW and two plant power generators with a capacity of 50MW.
Initial power began being generated as early as 2003, before construction of the dam body was even complete. But it wouldn’t be until 2012 that the dam would be fully operational and a hydroelectric power plant. In 2015 it was reported that annual electricity generation averaged 87TWh - 20 times more than the Hoover Dam. At its peak in 2018 it generated 101.6 TWh (though has yet to overcome the world record of 103.1 TWh set by the Itaipú Dam in 2016)

At full capacity the dam can produce enough energy to offset 31 million tonnes of coal consumption per year, reducing greenhouse gas emissions by 100 million tonnes per year. On average it produces around 1.7% of electricity demand throughout China.

50 Years of Engineering

To celebrate Fircroft’s 50th anniversary we’ve been looking at a major engineering feat made each year from 1970-2020. Read last week’s look back at 2005 and the launch of the world's largest passenger airliner.
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Building the world's biggest dam - Time to read 3 min
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