Tuesday’s marvels of engineering: Three Gorges Dam
Source: Pixabay

Three Gorges Dam, dam on the Yangtze River (Chang Jiang) just west of the city of Yichang in Hubei province, China.

A straight-crested concrete gravity structure, the Three Gorges Dam is 2,335 metres (7,660 feet) long with a maximum height of 185 metres (607 feet). It incorporates 28 million cubic metres (37 million cubic yards) of concrete and 463,000 metric tons of steel into its design. When construction of the dam officially began in 1994, it was the largest engineering project in China. At the time of its completion in 2006, it was the largest dam structure in the world.

Submerging large areas of the Qutang, Wu, and Xiling gorges for some 600 km (375 miles) upstream, the dam has created an immense deepwater reservoir allowing oceangoing freighters to navigate 2,250 km (1,400 miles) inland from Shanghai on the East China Sea to the inland city of Chongqing. Limited hydroelectric power production began in 2003 and gradually increased as additional turbine generators came online over the years until 2012, when all of the dam’s 32 turbine generator units were operating.

Reservoir province
Reservoir province
Source: Britannica.com

Those units, along with 2 additional generators, gave the dam the capacity to generate 22,500 megawatts of electricity, making it the most productive hydroelectric dam in the world. The dam also was intended to protect millions of people from the periodic flooding that plagues the Yangtze basin, although just how effective it has been in this regard has been debated.

Three Gorges Dam
Source: Britannica.com

History And Controversy

First discussed in the 1920s by Chinese Nationalist Party leaders, the idea for the Three Gorges Dam was given new impetus in 1953 when Chinese leader Mao Zedong ordered feasibility studies of a number of sites. Detailed planning for the project began in 1955. Its proponents insisted it would control disastrous flooding along the Yangtze, facilitate inland trade, and provide much-needed power for central China, but the dam was not without its detractors. 

Criticisms of the Three Gorges project began as soon as the plans were proposed and continued through its construction. Key problems included the danger of dam collapse, the displacement of some 1.3 million people (critics insisted the figure was actually 1.9 million) living in more than 1,500 cities, towns, and villages along the river, and the destruction of magnificent scenery and countless rare architectural and archaeological sites.

There were also fears—some of which were borne out—that human and industrial waste from cities would pollute the reservoir and even that the huge amount of water impounded in the reservoir could trigger earthquakes and landslides.

Some Chinese and foreign engineers argued that a number of smaller and far-cheaper and less-problematic dams on the Yangtze tributaries could generate as much power as the Three Gorges Dam and control flooding equally well. Construction of those dams, they maintained, would enable the government to meet its main priorities without the risks.

Because of these problems, work on the Three Gorges Dam was delayed for nearly 40 years as the Chinese government struggled to reach a decision to carry through with plans for the project. In 1992 Premier Li Peng, who had himself trained as an engineer, was finally able to persuade the National People’s Congress to ratify the decision to build the dam, though almost a third of its members abstained or voted against the project—an unprecedented sign of resistance from a normally acquiescent body.

President Jiang Zemin did not accompany Li to the official inauguration of the dam in 1994, and the World Bank refused to advance China funds to help with the project, citing major environmental and other concerns.

Nevertheless, the Three Gorges project moved ahead. In 1993 work started on access roads and electricity to the site. Workers blocked and diverted the river in 1997, bringing to a close the first phase of construction.

In 2003 the reservoir began to fill, the ship locks—which allowed vessels of up to 10,000 tons to navigate past the dam—were put into preliminary operation, and the first of the dam’s generators was connected to the grid, completing the second phase of construction. (Following completion of this second phase, some 1,200 sites of historical and archaeological importance that once lined the middle reaches of the Yangtze River vanished as floodwaters rose.)

City province Three gorges dam
Source: Britannica.com

Construction of the main wall of the dam was completed in 2006. The remainder of the dam’s generators were operational by mid-2012, and a ship lift, which allowed vessels of up to 3,000 tons to bypass the ship locks and more quickly navigate past the dam, began operating in late 2015.

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