Both Tan and Li said the quality of water in the Yangtze tributaries had deteriorated and outbreaks of algae or aquatic weeds had become more common.
"We can by no means relax our vigilance against ecological and environmental security problems or profit from a fleeting economic boom at the cost of sacrificing the environment," said Wang Xiaofeng, director of the office of the Three Gorges Project Committee of the State Council.
The open discussion of the negative effects of the Three Gorges Dam comes a month after the Wall Street Journal reported on the rising concerns of landslides, pollution and flooding in the area.
It quoted environmental scientist Weng Lida, secretary general of the Yangtze River Forum, as saying, "We thought of all the possible issues. But the problems are all more serious than we expected."
Commenting on the newspaper report, Wang said he thought most of the statements were said out of a concern for the Three Gorges Project, but some of the phrasing did reflect ulterior motives.
But he also admitted, "The problems mentioned in the Wall Street Journal should merit adequate attention from all of us."
Wang said the Chinese government had also paid great attention to consequences in the wake of the construction of the Three Gorges Dam.
Wang revealed that during an executive meeting of the State Council held earlier this year regarding the key problems arising from the Three Gorges Project, Chinese Premier Wen Jiabao was said to have cited ecological and environmental woes as primary problems to be addressed.
While pledging to cooperate more with relevant central and local government departments in promulgating regulations for tightening management over the reservoir, Wang said comprehensive management measures would be taken to ensure the water in the Three Gorges Reservoir is clean.
"We have to make concerted efforts to attain the dual goals of constructing a first-rate hydraulic project and making it into a top-level showcase for the environment," said Wang, "we will work harder to turn the Three Gorges Reservoir Area into an environmentally-friendly society."
The government has invested heavily in programs designed to restore and conserve the ecology of the Three Gorges area in recent years, including 12 billion yuan (about 1.5 billion U.S. dollars) spent on trying to harness geological disasters such as landslides.
It has also closed or relocated 1,500 manufacturing ventures, constructed more than 70 sewage disposal and waste treatment plants and resettled about 70,000 people from disaster-prone areas.
The participants in the forum in Wuhan also called for the establishment of a long-term mechanism on the prevention and control of geological disasters in the Three Gorges Reservoir Area, and a ban on fish farming in cages in the reservoir area to prevent an excess of nutrients degrading the water quality.
The Three Gorges Project, the world's largest water control facility, was launched in 1993, with a budget of 180 billion yuan (about 22.5 billion U.S. dollars).
Located on the middle reaches of the Yangtze River, the project boasts a 185-meter-high dam, completed in early 2006, and a five-tier ship lock. It has necessitated the resettlement of at least 1.2 million people.
Seventeen turbines - 14 on the northern bank of the Gorges and three more on the southern bank - are now in operation. They produced 23.77 billion kwh of electricity in the first half of the year, 2.65 billion kwh more than the same period last year.