Record-high water levels at China's massive Three Gorges Dam have called into question Beijing's claims that the world's largest hydroelectric project has capacity to withstand a massive flood.

On Friday, the water level reached 159 metres, only 16 metres away from the reservoir's maximum capacity of 175 metres, the official Xinhua News Agency said, citing reservoir engineers. Given the continued flooding, the levels could easily rise higher.

Minister of Water Resources Chen Lei urged those responsible to continue to inspect and protect dams and reservoirs as well as prepare for heavy rainfalls. Work teams have been dispatched to areas including Sichuan, Shaanxi and Gansu to co-ordinate flood-fighting efforts, Xinhua said.

China has for years promoted the Three Gorges Dam as the best way to end centuries of floods along the Yangtze River basin and dismissed complaints about the enormous environmental impact of the $24-billion reservoir that has displaced more than 1.4 million people.

Seven years ago, Chinese officials boasted that the Three Gorges Dam could withstand floods so severe they come only once every 10,000 years. But as the current flooding shows no sign of waning, officials warn that its capacity is limited.

Zhao Yunfa, deputy director of the China Three Gorges Corporation's dispatch centre, said this week that the dam's capacity can only withstand floods that reach up to 85,000 cubic metres per second — only about 18 per cent more than the dam's record water flow on Tuesday, the China Daily newspaper reported.

"The dam's flood control capacity is not unlimited," Zhao told the newspaper.

Since the completion of the Three Gorges Dam in 2006, confidence in its flood capacity has diminished as officials have backpedalled on their claims each year.

In 2007, officials said the dam could withstand the worst flood in 1,000 years. Then on Tuesday, the Three Gorges Corporation's chairman, Cao Guangjing, told China Daily he can "absolutely guarantee" the dam can withstand the worst flood in 100 years.

The Three Gorges Dam is located in central Hubei province, impounding China's largest river, the Yangtze, with 18,200 megawatts of generating capacity.