Xayaburi Dam and the Fate of the Mekong

December 6, 2011
By Andrew Howley
National Geographic

Representatives of the nations around the Mekong River are meeting this week to make a decision regarding the construction of a large new dam that would have varied and substantial effects throughout the region (read the backstory in this NG News article from March 2011).

National Geographic Emerging Explorer Zeb Hogan has worked extensively in the region, studying the river’s largest fish as a way of understanding the health of the freshwater system as a whole (see photos of the megafish threatened by the dams). Here he discusses the possible impacts of the proposed Xayaburi Dam and the importance of this week’s decision.

What are pros and cons of the proposed Xayaburi Dam?

Laos has said that it wants to be the “Battery of Asia” and has plans for approximately 55 dams to produce hydropower to export to neighboring countries. This hydropower comes at a cost however. While dams will produce electricity that will provide much needed income for Laos, mainstream Mekong dams can impair ecosystem services worth billions of dollars a year.

One recent study estimated that the cost to replace these ecosystem services could be as high as $274 billion. Millions of people, hundreds of fish species, and the fate of the Mekong hand in the balance, and so it’s not a decision to be taken lightly. The developer of hydropower should be forced to internalize any environmental or social costs, something which has not happened to date.

If they prevent the dam today is that the end of the story, or might it still get built?

The dam could still be built, but as more research is done the true costs and benefits will become more apparent, as will alternatives to mainstream Mekong hydropower. For example, one recent study showed that tributary dams (as opposed to mainstream dams) could be a more environmentally friendly way to produce power for the region. Mitigation measures may also improve over time, making dams less environmentally damaging.

Are there other major dams in discussion on the Mekong?

Yes, there are 22 dams proposed, approved, or built on the mainstream Mekong in China. There are a total of 12 mainstream dams at various stages of consideration on the lower Mekong (Thailand, Lao PDR, Cambodia, and Vietnam). The Xayaburi Dam is significant because it would be the first mainstream dam in the lower Mekong, the area of highest diversity and productivity. All of the numbers that you see about the importance of Mekong fisheries–largest in the world, 2.5 million tons/year, values at $3-6 billion/year–refer to the lower Mekong. The lower Mekong fishery is dominated by migratory fish that are most vulnerable to the impacts of mainstream dams.