Three Gorges Dam

While much of China's vast countryside is only covered by low-res imagery, Google recently released new high-res images of the area around the dam, giving us our first real chance to write about it.

First conceived around 90 years ago, the proposed dam was strongly supported by Chairman Mao in the 1950s. However, it wasn't until the mid-90s that construction finally began on the dam, which is over 2km wide and 185m high.

The statistics surrounding this project are staggering:

• A total cost of 180 billion yuan ($30 billion US), an amount which is actually below budget, and which will be recovered with ten years of power generation.
• Construction used more than 27 million cubic metres of concrete and 463,000 tonnes of steel.
• Over a hundred million cubic metres of earth were moved
• Around 22,500 MW of electricity will be created by 32 primary generators once maximum capacity is reached within the next year.
• While this was expected to be 10% of national demand for power, industrial growth across the country means that it will now be less than 3%.

Fourteen of the generators are found on the north end of the dam, with twelve on the south side¹, separated by the spillways. Six more are located below a nearby mountain.

Immediately to the north of the dam is a ship lift which is still under construction, with completion expected in 2014. It will be capable of moving ships up to 3,000 tons through the 113m vertical difference between water levels.

Beyond the lift is a series of locks for vessels up to 10,000 tons, which take about 4 hours to transit. Coupled with safer water caused by higher water levels in the gorges, these locks have allowed a tenfold increase in the amount of freight on the river – leading to a significant reduction in emissions from the trucking industry. Hydro power is also considerably cleaner than the coal power plants which are the norm in China.

However, there are concerns about serious environmental impacts caused by the dam, including the destruction of wetlands and habitat for a variety of animals. Riverbank erosion and landslides are another major concern.

There was also a significant human impact, with more than a million people forced from their homes and farms along the Yangtze. Significant historical and archaeological sites were also submerged.

The famous three gorges are Qutang, Wu and Xiling, and are mostly still covered by old low-res imagery which doesn't show today's higher water levels.

Recent heavy rains lead to flooding in the region and was a serious test of the dam's strength, with water rising to within 20m of maximum capacity. Authorities claim that the dam helped prevent disastrous flooding downstream. The BBC has a spectacular video showing excess water being expelled from the slipways.

You can read more at Wikipedia, and at the dam's official site, which puts a slightly more positive 'spin' on the issues surrounding the project than has been presented in the world's media.

Thanks to Dan, Sebastian Nebel, woowoowoo, Peter Donohue, t.r.mcloughlin, luluwing, Chris Yao, Marco Rodrigues, terLag, xlk, Jonathan Crone and Adam.