How the Next 12 Months of Xayaburi Dam Construction Will Affect the Mekong River

Kirk Herbertson
From Poyry's July 16th presentation on next steps of Xayaburi construction (part 1)

The Xayaburi Dam site in Laos is abuzz with activity these days. Thousands of laborers and dozens of construction vehicles work around the clock to finish the dam on schedule by 2019. Access roads, worker camps, and transmission lines have been built. Villages are being resettled. The river has already been widened at one point, and a dike cuts into the river at another point. One of the project’s lead engineers, the Pöyry Group, told a delegation of visiting diplomats last week that the coffer dam – which diverts the river while the permanent dam is built – will be completed by next May. Soon after that, the dam itself will begin to appear.  

Laos’ rapid progress on the dam worries its neighbors. The Mekong River is a shared resource, and what happens upstream in Laos can affect people downstream in Thailand, Cambodia and Vietnam. According to the 1995 treaty that governs use of the Mekong River, the governments of Cambodia, Laos, Thailand and Vietnam must jointly decide if the Xayaburi Dam will go forward. No decision has yet been reached. Cambodia and Vietnam have both requested that transboundary impact studies be completed before a decision is made, but Laos has said it will not conduct these studies. A regional diplomatic crisis may soon erupt.

Construction hasn’t started?

Proceeding with construction at this early stage would be a clear violation of the 1995 Mekong Agreement and international law. Not to worry, Laos spokesperson Viraphonh Viravong told the Bangkok Post last week. “We have not started working on any construction on the Mekong River that is permanent.” 

From Poyry's July 16th presentation on next steps of Xayaburi construction (part 2)

Yet the 1995 Mekong Agreement makes no distinction between “permanent” and “temporary” construction activities along the river. It worries instead about any activities that would cause “harmful effects” to the river’s ecosystems. Similarly, international law (the rules that govern how states treat one another) kicks in when the harmful effects are likely to be transboundary, as they are in this case.

As it turns out, many of the construction activities already underway at the dam site are likely to have harmful effects on the Mekong River. 

Yes, construction affects the river

As the Mekong River Commission noted in its 2011 technical review of the proposed Xayaburi Dam, “impacts during the construction phase are equally as important as those during dam operation.” (p. 32) Based on experiences with other dams, here are just a few of the impacts we might see in the next 12 months if construction continues:

  • The coffer dam and other structures will divert the river, which could prevent fish from migrating past the dam site and block sediment flows downstream.
  • As extra sediment becomes loosened during construction and mixes into the water, it could change water quality, habitats, and the ability of fish to breathe. This could lead to declining fish populations.
  • Loosened sediment could bury and harm fish eggs.
  • Pollution from the construction site could affect water quality and alter ecosystems, harming fisheries and agriculture downstream.
  • Disturbances to the river could affect plankton and microorganisms that are important to the stability of the river’s ecosystem.
  • Resettlement of local communities could create food security problems, based on experiences in the first resettled village.
From Poyry's July 16th presentation on next steps of Xayaburi construction (part 3)

What happens in Laos in the next 12 months will not just be localized. The construction phase is likely to have significant impacts that can be felt downstream in neighboring countries.

Pöyry, CNR, and the art of making scientific-sounding promises

Yet we still do not know the full extent of the harm that the Xayaburi Dam’s construction phase will cause. Laos’ consultants Pöyry Group and Compagnie Nationale du Rhône (CNR) do not know either. Despite Cambodia’s and Vietnam’s formal requests over one year ago, Laos has still not studied the baseline conditions of the river. How do fish behave in this part of the river, for example, and how do people downstream depend on these fish? It is simply not possible to understand the full extent of the dam’s impacts without first gathering this data. This is one reason why many scientists are skeptical about the unequivocal promises by Pöyry and CNR that the project will have minimal environmental impacts.

From Poyry's July 16th presentation on next steps of Xayaburi construction (part 4)

The 1995 Mekong Agreement is not perfectly written by any means, but is the best framework the region’s governments have for reaching a mutually acceptable solution. Where there are gaps, international law can provide guidance – such as the requirement to assess transboundary impacts before proceeding with any construction. 

The time has come for the Mekong governments to bring Laos back into compliance with the 1995 treaty, and to return to the structure that the treaty provides. The first step, as the Cambodian government has already requested, is for all construction activities on the Xayaburi Dam to stop while further impact studies are carried out. 

From Poyry's July 16th presentation on next steps of Xayaburi construction (part 5)

Ten more dams have been proposed for the Mekong River, eight of them in Laos. No one wants to repeat the chaos of Xayaburi, or to learn a few years from now that we could have prevented all of the harm that the Xayaburi Dam will soon bring.


Kirk Herbertson is a lawyer and Southeast Asia Policy Coordinator for International Rivers.