TO THE many fishing and farming families living on the banks of the Mekong River in Cambodia, the sigh of the endangered Irrawaddy dolphin is part of the soundtrack of their lives. But that could change - and very soon too.
Almost 5,000km long and running through China, Myanmar, Laos, Thailand, Cambodia and Vietnam, the Mekong feeds some 60 million people. With 877 species of fish recorded, it is the second most biodiverse river system in the world after the Amazon.
Studies have put its value as an inland fishery at more than US$3 billion (S$3.8 billion) annually. This value is the greatest in the lower reaches, where the river fans out across the Lao and Cambodian plains, swelling with water in the monsoon season and filling out Tonle Sap, Cambodia's sprawling inland lake.
Yet, the demand for energy has led to plans for as many as 11 hydroelectric dams - nine in Laos and two in Cambodia - to be constructed on the Mekong and even more on its tributaries. By 2030, there will be a staggering 77 dams across the Mekong basin. Construction is under way for some, and completed for others.
In China, where the Mekong is known as the Lancang, six dams are either ready or being built.
The scramble for revenue-earning hydroelectric power has caused friction among the ASEAN neighbours.
Laos, with ambitions to become "the battery of South-east Asia", last year began construction of the Xayaburi dam on the Mekong mainstream despite the objections of downstream neighbours Cambodia and Vietnam.
The latest bone of contention is the proposed Don Sahong dam, which Laos will build near the border with Cambodia.
Its construction threatens the livelihoods of fishermen downstream and could wipe out a small population of endangered Irrawaddy dolphins in Cambodia, conservationists and critics have warned.
Last month, at a meeting of the Vientiane-based intergovernmental Mekong River Commission (MRC), Cambodia, Laos, Thailand and Vietnam agreed to refer the matter to the MRC Council, which comprises water and environment ministers.
The council is to decide whether building the Don Sahong dam warrants "prior consultation" with Laos' neighbours before it proceeds, or whether only "notification" is required.
Laos maintains that since the dam will affect only about 15 per cent of the water volumes in the area, this is not significant enough to warrant "prior consultation", which means it can go ahead with the project unilaterally. As in the case of Xayaburi dam, there is nothing to stop it.
However, at least one study says that the 256MW Don Sahong dam will reduce fish populations downstream by up to 30 per cent.
"The dam will block the only channel suitable for year-round fish migration, putting the world's largest inland fishery at risk," the World Wide Fund for Nature (WWF) said in a report last Thursday.
Balancing priorities will not be easy. The only certainty is that the exploitation of the Mekong will transform the entire landscape over the next five to 10 years, changing irrevocably the character of a transnational ecosystem in ways that are as yet poorly understood. This will increase friction, both within and between countries.
Sharing the Mekong and managing the far-reaching changes is already testing relationships - but this is only the beginning.
Hydroelectricity qualifies as renewable energy and brings in hard cash, mostly from sales to neighbours like Thailand. The consequence of building dams for poor but resource-rich countries like Laos will also be far-reaching and involve many trade-offs.
But there will be contentious issues for years to come. They will include the way revenues are allocated, how thousands of families are resettled from dam sites, and what changes in environmental and food security will be triggered by manipulating the hydrology of a complex ecosystem.
At a forum on the Don Sahong dam at Bangkok's Chulalongkorn University last week, environmental groups discussed the ramifications of the project. But as former Thai senator Kraisak Choonhavan stressed, the discussions taking place in the airy, high-ceiling room were far removed from the reality at the Mekong.
Laos, one of the poorest and least developed countries in South-east Asia, is well within its rights, prior consultation required or otherwise, to build the dam. At this moment, at least, no environmental movement is capable of changing that, Mr Kraisak said.
According to the WWF, there are only 85 Irrawaddy dolphins left in the Mekong.
They bring in revenue for Cambodia from tourists who pay US$9 for an hour on a boat to look for the rare mammals.
Building the Don Sahong dam will entail blasting rocks, sending shock waves through the area, and will cut off the migration path of fish that use the channel. This will precipitate the extinction of the dolphins.
Without a long-term vision for managing changes on the Mekong, the sigh of the dolphin will fade into silence.
More importantly, the fate of these endangered mammals is but a barometer of the future - of the tens of thousands of people whose lifeline is the Mekong.
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