The Three Gorges Dam, the world's largest dam, takes the strain for the first time today when the temporary dam that has protected it throughout construction is demolished.

The cofferdam protecting the just-completed Three Gorges Dam is refilled with water in Yichang, central China's Hubei Province, June 3, 2006. Demolition experts completed Friday the setting of explosives that will create a massive explosion to demolish the cofferdam on June 6. [Xinhua]
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A network of electronic triggers was completed on Sunday for today's demolition of the last cofferdam holding back the Yangtze upstream from the Three Gorges Dam in Yichang, Central China's Hubei Province.

The electronic trigger network is attached to 2,540 detonators, which will set off nearly 1,000 consecutive explosions using a total of 192 tons of dynamite to blow up the cofferdam.

Zhang Chaoran, chief engineer of the China Yangtze Three Gorges Project Development Co, said the demolition was a challenging job, but he was confident it would be a success.

Song Ling, general manager of Chongqing Gezhouba Yipuli Chemical Company, who will oversee the demolition, told the Xinhua News Agency that all preparatory work was now completed.

Zhao Gen, a senior engineer with the Yangtze River Academic Institute and designer of the demolition project, said the demolition of the vast temporary dam would only take about 12 seconds.

The removal of the cofferdam means the Three Gorges Dam, completed on May 20 this year, will begin its flood control role two years ahead of schedule and in time for the 2006 flood season, which usually begins in June.

The cofferdam, which has held the reservoir since 2003, is 580 metres long, 140 metres high and 8 metres wide at the top.

Debris from the explosion has been estimated at 180,000 cubic metres.

The Three Gorges Dam has been engineered to prevent and control floods and "even in the rare occurrence of a 1,000 year flood, mass damages or injuries can still be prevented," according to Zhang.

Deadly floods are a frequent occurrence along the Yangtze, China's longest river and the world's third longest after the Nile and the Amazon.

The floods have claimed more than a million lives in the past century, with the latest flood, in 1998, responsible for about 1,000 deaths and approximately 100 billion yuan (US$12.5 billion) of damage.

At 185 metres high and 2,309 metres long the Three Gorges Dam uses 28 million cubic metres of concrete.

Launched in 1993, the 180-billion-yuan (US$22.5 billion) project to build it involves three stages.

The entire project is expected to be finished in 2008.

Designed for power generation as well as flood control, when operating at full capacity the dam's generators are expected to produce 18.2 million kilowatts of energy up to one ninth of China's output.

Despite the advantages, environmental problems along the Three Gorges reservoir are serious.

Just to prevent garbage from piling up at the dam, China will have to spend at least 10 million yuan (US$1.3 million) annually, to ensure the safe operation of the world's largest water control project.

Statistics suggest that the garbage runoff flowing into the reservoir will amount to 100,000-200,000 cubic metres each year, most of which will accumulate in flooding seasons.

Editor: Yan