China’s Three Gorges Dam, currently the world’s largest hydroelectric dam, began construction in 1994 and cost around £29 billion over its nine-year build.
Situated in Hubei, a central province of China, the dam crosses the Yangtze River, the longest river in Eurasia.
At a height of 181 metres and a length of 2,335 metres, it is capable of holding a staggering 27.2 million cubic metres of water and has a maximum capacity of 22,500 megawatts. When operating at full capacity, the Three Gorges Dam can power 5.4 million households for one month, using the flow of water from nearby gorges Qutangxia, Wuxia and Xilingxia.
The catastrophic 2004 Boxing Day earthquake and tsunami in the Indian Ocean first prompted scientists at NASA to investigate the idea that the Earth’s rotation could be affected.
In physics, the distribution of mass on Earth can have a small influence on the planet’s “Moment of Inertia” – a concept that describes how difficult it is to rotate an object around a given axis, IFL Science reports.
The motion of tectonic plates during and after an earthquake was deemed to have affected the Earth’s spin, with the 2004 earthquake in particular having altered the planet’s mass distribution and decreased the length of a day by 2.68 microseconds.
In a post from 2005, Dr Benjamin Fong Chao, a geophysicist at NASA’s Goddard Space Flight Center, explained that the huge amount of water that was shifted in order to fill the Three Gorges Dam, could have the same effect. This shift of mass would increase the length of a day by 0.06 microseconds and move the pole position of Earth by about two centimetres, he determined.
The effect may be insignificant to our everyday perception, but it could lead to confusion for super-accurate time-keeping devices like atomic clocks.
The ensuing problem has led some scientists to argue that the world will need to account for a negative leap second – such as a minute with just 59 seconds – within the next decade.
A total of 1.3 million people had to be rehomed during the construction process of the Three Gorges Dam, as their towns and villages were flooded.
As well as producing electricity, the dam is intended to increase the Yangtze River’s shipping capacity and reduce the likelihood of floods downstream by providing flood storage space.
The government considers the project a historic engineering, social and economic success, using state-of-the-art large turbines and a move toward limiting greenhouse gas emissions.
However, its construction is not without its controversies – precious archaeological and cultural sites were flooded. Other critics argue the dam has had a significant impact on the environment and has increased the risk of landslides.
The project used 27.2 million cubic metres of concrete, 463,000 tonnes of steel (enough to build 63 Eiffel Towers) and moved about 102.6 million cubic metres of earth.