It took less than 13 seconds yesterday for nearly 200 tons of explosives to tear down the Three Gorges cofferdam, built in 2003 to enable construction of the main dam.

Li Yong'an, in charge of the 4 pm directional blast, declared the demolition a success.

The explosion blew away the upper 30 metres of the cofferdam, which is 140 metres high and 8 metres wide at the top.

The under-water part was left intact because it will not affect the water flow of the Three Gorges Dam.

The blasted parts of the temporary dam flew in the direction away from the main dam and fell at the foot of the remaining cofferdam, so posing no threat to the main wall which is about 100 metres away.

Debris from the explosion was measured at 180,000 cubic metres.

Fish stocks were driven away about three hours before the explosion, Xinhua News Agency reported.

Biologists used special devices to create high-pressure electric pulses in water to dispel fish schools near the cofferdam, including such rare species as Chinese sturgeon, river dolphins and mullet.

The explosion did not affect other parts of the Three Gorges Project, said Li, general manager of China Yangtze River Three Gorges Project Development Corporation.

"The rising water volume after the blast will not have any geological impact," said Li.

That's because the mega dam had been constructed on a complete granite structure which has a stable trait, Li pointed out.

With the temporary dam gone, the water level in the reservoir is expected to reach 156 metres after the flood season this summer, experts said.

When the level reaches 175 metres, the reservoir would hold 22.15 billion cubic metres, which means the Three Gorges Project can control even heavy floods and at least 15 million residents of the middle and lower reaches of the Yangtze River can be safe.

In 2011, all the 32 generators of the Three Gorges Project will go into operation with an annual output of 100 billion kilowatt-hours, which would entail savings of 50 million tons of coal every year.

The annual electricity output of the project will be equal to 5 per cent of the country's total power consumption.

As the world's biggest water control project, the Three Gorges Project was initially envisaged in 1919 by Sun Yat-sen, the forerunner of China's democratic revolution.

It was a subject of hot debate and extensive research for half a century before it was finally approved in 1992 by the National People's Congress, the top legislature. Construction began in early 1993.

By the end of 2009, a total of 1.13 million residents in the reservoir areas of the project will move to other places with the support of local governments.

Source: China Daily