From its crystalline beginnings as a rivulet seeping from a glacier on the Tibetan Himalayas to its broad, muddy amble through the jungles of Myanmar, the Nu River is one of Asia's wildest waterways, its 1,700-mile course unimpeded as it rolls toward the Andaman Sea.
But the Nu's days as one of the region's last free-flowing rivers are dwindling. The Chinese government stunned environmentalists this year by reviving plans to build a series of hydropower dams on the upper reaches of the Nu, the heart of a UNESCO World Heritage site in China's southwest Yunnan province that ranks among the world's most ecologically diverse and fragile places.
Critics say the project will force the relocation of ethnic minorities in Yunnan and destroy the spawning grounds for endangered fish species.
Geologists warn that constructing the dams in a seismically active region could threaten those living downstream. Next month, UNESCO is likely to discuss whether to include the area on its list of endangered places.
Among the losers could be the farmers and fishermen who depend on the Salween, as the river is called in Southeast Asia. "We're talking about dams that will alter the resources for communities that depend on the river," said Katy Yan, China programme coordinator at International Rivers.