The Three Gorges Dam project failed to consider the full impact it would have on the ecological environment during its early design, an official admitted yesterday.

But he said the impact could be minimized by proper water discharges from the reservoir to the Yangtze River.

The dam, the world's largest hydroelectric project, had contributed to the lowered water levels of Dongting Lake in Hunan Province and Poyang Lake in Jiangxi Province, Wang Jingquan, deputy inspector of the flood control and drought relief office affiliated to the Yangtze River Water Resources Committee, told Xinmin Evening News.

China's two largest freshwater lakes are drying up during the current drought in the middle and lower reaches of the Yangtze River.

The level of the Yangtze River would be lower after the dam's reservoir began storing water in October every year, thus causing water from the two lakes to pour into the river, Wang told the newspaper.

Water levels of the Poyang Lake had been above 19.5 meters but dropped to just 16 meters after the main part of the dam was completed in 2006, according to Tuesday's Oriental Morning Post.

The State Council, China's Cabinet, has approved bringing forward the water storing period of the reservoir by a month, to September, when both the Yangtze River and the lakes had sufficient water, Wang said.

The dam also had an impact on the wildlife and plants in lower reaches of the Yangtze, said Wang. It made the water in the river flow more slowly and that had affected fish breeding patterns. The lower water levels had an effect on the growth of some water plants, he added.

He said the committee was still looking for solutions to the impact on the river's ecosystem.

"We failed to think of all the impacts that the dam might bring about when designing the dam, but its advantages should outweigh the disadvantages," he said.

Apart from generating more than 80 billion kilowatt-hours of "green power" a year, the project effectively prevented flooding and enabled heavier ships be able to sail on the Yangtze, Wang said.