The natural flow of the Yangtze river was brought to a halt yesterday as engineers at the Three Gorges dam, under construction in central China, closed a crucial section.
A diversion canal, which had allowed the river to flow freely around the dam as it was being constructed, was finally blocked.
The water will now pass through sluice holes until next year when more work will have been completed and a reservoir upstream begins to fill.
The damming ceremony was watched by the senior Chinese leader Li Peng on the eve of the 16th Communist party congress which starts in Beijing tomorrow.
Mr Li pushed through the controversial project in the clampdown following the 1989 Tiananmen square massacre — in which he played a dubious role.
He is now expected to retire from high office in the coming months alongside President Jiang Zemin. The official press has loyally hailed the dam as a triumph for the party’s leadership.
Engineers seized the chance to plug the final 15-metre gap in the diversion canal when the Yangtze’s water flow slackened to less than 10 000 cubic metres a second. Raising the level of the 400-kilometre reservoir, which extends upstream as far as the city of Chongqing, will begin next July.
A huge clean-up is under way to prevent the reservoir from being filled with rubbish and effluent.
Project officials admitted that they were working to a very tight schedule with no room for delay.
The clean-up is described as arduous work and includes the removal of burial grounds as well as industrial waste.
Last month, work on an essential waste-water treatment plant at Chongqing was delayed by angry residents who said they had not been properly compensated for losing their land.
Work on the dam began in 1993 and will be completed in 2009.
More than 646 000 people have been moved from their homes so far, 140 000 of them to other Chinese provinces.
Thirteen new towns have been built to house the evicted families and industries, and more than 800 kilometers of new roads have been laid.
The Yangtze river has already been dammed once at the Gezhouba dam — completed in 1981 about 20 kilometers downstream. – Guardian Unlimited Â