Officials and experts in Beijing debated at the weekend a plan to harness the Nu River in southwest Yunnan province with a chain of up to 13 hydro-power stations amid signs of revived official favour for the project.
The whole project, which could take a decade or more to build, would generate more power than the mammoth Three Gorges Dam, and displace 50,000 farmers, say supporters.
But opponents claim it will tear the region's delicate social and environmental fabric with little benefit to locals. They have recently circulated a petition urging the government to release studies of the dams' environmental impact and allow greater public debate.
Chinese Premier Wen Jiabao halted the project and ordered further studies early last year after a pioneering public campaign by opponents that was backed by China's top environmental protection agency.
Chinese conservationists, however, now say official reluctance to release the environmental impact studies may conceal moves to revive the dams and stifle debate about controversial projects.
Supporters struck back at the weekend meeting, arguing the dams will bring electricity and jobs to the remote corner of China and ease pressures on the environment, according to people who attended.
The unusually open controversy over the Nu River's fate is emerging as a test of the government's openness and priorities, just a week after it released a draft five-year development plan urging a halt to environmental destruction while still pushing for rapid economic growth.
Like other controversial hydro projects, including the Three Gorges Dam and proposals to dam the nearby Leaping Tiger Gorge, it highlights the contentious trade-offs China must make between development and conservation. It must also choose between saving its rivers or cutting pollution from coal-fired power stations, which supplies three-quarters of China's electricity.
The Nu cascades from glaciers in Tibet down a 300 km (180 mile) gorge and critics say damming it will spoil one of China's few pristine environments and threaten communities and wildlife downstream into Southeast Asia, where it is called the Salween.
Ma Jun, a Beijing-based environmental consultant who opposes the project and drafted the petition, said China faces hard choices between economic development and environmental protection. But too often, he added, lack of public participation has encouraged officials -- eager to make their stamp with large engineering projects -- to dismiss environmental concerns.
"We recognise this is a difficult case, but you can hardly accept such a major project without some outside involvement," said Ma. The petition issued on August 31 has been signed by 61 groups and 99 individuals, among them Greenpeace and Friends of Nature, China's largest environment association.
But project supporters, including senior officials, dominated the weekend meeting, sponsored by a magazine run by the pro-development National Reform and Development Commission, a super-ministry in charge of economic policy.
"We're confident the project will go forward," said Liu Shunning, an organiser of the meeting.
China's environment can be protected only if the country first spreads economic growth, said He Zuoxiu, a prominent scientist who attended the meeting and supports the dams.
"To really protect the environment there, the locals must escape from poverty to prosperity," He told Reuters. "And at present the only viable measure to take is developing hydro-electricity."
The project would generate 4,000 more megawatts of electricity a year than the Three Gorges Dam, now the world's largest hydro-electric project, which will generate 18,000 megawatts when finished in 2009.
China has suffered widespread power shortages and supporters say more dams will ease dependence on polluting coal-generated power. Project critics say China may face a power glut by next year and cutting energy waste comes first.
He, 78, said he visited the Nu River earlier this year and co-authored a report endorsing the project, which he sent to China's leaders in May. It attracted "high-level approval", he said. China's Ministry of Water Resources and Yunnan province government were working on revived plans for the dams, he added.
In July, Yunnan officials lobbied Premier Wen to restart the Nu River project. Wen instructed central government ministries to "set forth their views as quickly as possible", Hong Kong's Wen Wei Po, a Beijing backed newspaper, reported in September.