The roaring currents of the Mekong have long enchanted travellers, inspired explorers and sustained about 65 million people living off the world's largest freshwater fisheries.
But environmentalists warn that the 'Amazon of Asia' - the river with the second-richest biodiversity in the world - is under dire threat from hydropower dams, including the latest to be proposed: the Xayaburi dam in Laos. Authorities in Laos have put their faith in hydropower as a formula to lift the nation out of chronic poverty by selling electricity to Thailand and Vietnam.
The Laotian government notified the Mekong River Commission in September of its plans to build a dam at Xayaburi, in co-operation with a Thai private company.
It has triggered alarm bells among environmental scientists, non-government organisations and river communities about a headlong rush into dam building before the environmental impact has been fully understood.
'There is a very fast pace of hydropower development, passionately fast,' Juta Sarkkalen, a Mekong specialist from Helsinki and based in Vientiane, said. 'We need a time out. We need a moratorium on dams to consider a different strategy of development.'
China has already built four dams on the Lancang (the Chinese stretch of the Mekong), including the tallest high-arch dam in the world, at 292 metres.