In an unusually frank public admission of problems associated with the construction project, Qian Zhengying, a former minister of water resources and electric power who heads the dam’s quality-control inspection group, said the turbines are not ideally suited to the conditions in which they will be operated, but it is too late to do anything about it.

"The die is cast, since we have signed the contracts with the suppliers," she said.

She also expressed concern that cracks could appear in the turbines, particularly the ones made in China, because of possible "flaws and weaknesses" in their manufacturing or installation.

Ms. Qian spoke to project officials on April 8 after her team of experts spent a week investigating problems at the construction site. Her remarks were published in the Three Gorges Project Daily (Sanxia gongcheng bao) on April 11.

"When we invited tenders for the turbines years ago, we assumed they would be operating with the reservoir water level high," Ms. Qian said. "Based on this assumption, we placed special emphasis on several key technical parameters in the design and manufacture of the turbines.

"But now things have changed, given that the turbines will be operating with the reservoir water level low for most of the year, as all of us have now realized. … [W]e are really concerned about the big difference between the operating conditions we assumed when inviting tenders years ago, and the actual conditions that will pertain when the turbines are put into operation a year and half from now."

She said that how the turbines will operate "under these changed circumstances" remains a major question. And she noted that "the key to promoting economic benefits and repaying loans depends on being able to generate electricity."

The turbines’ power output will depend on how much water is stored behind the dam, and they will generate less electricity than originally projected if the water level in the reservoir is kept low. Ms. Qian gave no details about this apparent change in operating regime.

"What we most need to rethink is how and why we created such a big problem by selecting this particular design and structure for the turbines in the first place," she said.

GE Canada is a member of a consortium including Siemens and Voith of Germany and Sade Vigesa of Brazil that is supplying six of the dam’s 26 turbine-generator units. GE Canada is building three of the units at its plant in Lachine, Que. Canada’s Export Development Corp. provided a US$153-million loan to finance the deal. Alsthom of France is supplying another eight generators.

Ms. Qian said cracks have also appeared in the concrete dam itself, and in the giant five-stage ship-lock, the biggest of its kind ever built. She revealed that the "flaws and cracks" on the surface of the ship-lock were so severe that her team of experts had almost been forced to call a halt to construction.

"Special care needs to be taken to ensure the solidity of the concrete, since hollows and other flaws are still being found in some places on the surface of the ship-lock," she said.

"You and I will both be blamed if we cannot sail our boats on the Yangtze after the Three Gorges dam is completed."

The cracks in the dam were caused by a failure to keep sections of concrete warm during hardening. More attention must be paid to temperature variations during concrete pouring, especially because an unusually hot summer is expected this year, she said.

"The concrete-pouring has not been first-class, and cracks in the dam have been discovered," she said. "Perhaps the inspection group should be held responsible for the consequences. Why? Because we failed to remind you to continue to keep the poured sections warm after we discovered in the winter of 2000 that you were no longer doing this."

She cautioned project officials that quality-control issues must not be sacrificed in the race to start generating electricity – and repaying the project’s huge debts.

"From my own experience, I have seen the following scenario on many occasions: Today a brand-new hydropower station starts generating electricity after a grand ceremony celebrating the completion of the project – and the next day the station has to cease operating for a lengthy period of inspection and repair," she said.

"Some projects have become unable to generate electricity at all, and, even if they are able to produce electricity, others have had difficulty reaching the designed generating capacity."