Catching fish in the Khone Falls area, Southern Lao.

Mekong Mainstream Dams

The revival of plans to build a series of dams on the Mekong River's mainstream in Laos and Cambodia presents a serious threat to the river's ecology and puts at risk the wellbeing of millions of people dependent on the river for food, income, transportation and a multitude of other needs.

The prospect of developing the Lower Mekong River's hydropower potential has long been of interest to governments in the region with plans being drafted as early as 1960. However, the process was begun in earnest in mid-2006, when the Governments of Cambodia, Laos and Thailand granted approval to Thai, Malaysian, Vietnamese, and Chinese companies to investigate eleven mainstream hydropower dams. The projects are located at Pak Beng, Luang Prabang, Xayaburi, Pak Lay, and Sanakham in northern Laos; Pak Chom and Ban Koum near the Thai-Lao border; Phu Ngoy (formerly Lat Sua) and Don Sahong in Southern Laos; and Stung Treng and Sambor in Cambodia (see map). If all of these projects are built they will transform the one of the world’s most iconic rivers, and the second most biodiversity river globally, into a series of reservoirs. Xayaburi and Don Sahong have already begun construction and preparatory work has commenced for Pak Beng, the third dam to move forward on the Mekong mainstream. These three dams alone are predicted to have negative transboundary impacts on the environment and people through the Mekong Basin. If the remaining eight proposed dams are built, they seriously jeopardize the future of the Mekong as a life-sustaining ecosystem.

Serious concerns have been raised by non-governmental organizations and scientists over the Xayaburi Dam, which is at the most advanced stage of development with an estimated 70% of the project now complete as of May 2017. In September 2010, this dam became the first mainstream dam to be submitted for approval by the region's governments through a set of regional decision-making procedures called the ‘Procedures for Notification, Prior Consultation and Agreement’ (PNPCA), facilitated by the Mekong River Commission (MRC). This leapfrogged the publication of the MRC's Strategic Environmental Assessment (SEA) report by a mere three weeks, which provided a critical appraisal of the dam plans and recommended that decisions on whether to proceed with the mainstream dams be deferred for a period of ten years until further studies could be conducted to ensure that decision-makers were fully informed of the risks. 

The Lao Governments decision to build the Xayaburi Dam, as the first of nine proposed mainstream dams in the country, directly ignored the recommendations of the SEA. It set a dangerous precedent in the MRC, as construction began without first addressing the concerns of downstream countries. This was repeated in the decision to proceed with Don Sahong, which began construction in 2016. Critically, no transboundary assessment was conducted, despite the dam’s location only 2 kilometers from the Laos-Cambodia border and despite requests for these studies from Cambodia and Vietnam. The Lao Government appears set on rapidly expanding its hydropower resources as Prior Consultation is underway for Pak Beng, the third project on the Mekong mainstream, and preparatory work on the dam has already begun.  

The rapid expansion of hydropower and its predicted irreversible transboundary impacts on the environment and people across the region who depend on the Mekong River, threatens the development of all countries who share the Lower Mekong Basin, with downstream Cambodia and Vietnam at greatest risk. It is crucial that the Mekong region’s decision-makers re-evaluate their plans to dam the Mekong, before it is too late. The SEA’s recommendations should be adopted so that large scale damming of the Mekong does not occur until the impacts of doing so are fully known. As millions depend on the Mekong and the resources it provides, there is too much at stake to proceed with the cascade of dams without greater knowledge of the enormous risks posed.

China's dam construction on the Upper Mekong has already caused downstream impacts, especially along the Thai-Lao border where communities have suffered declining fisheries and changing water levels that have seriously affected their livelihoods. By changing the river's hydrology, blocking fish migration and affecting the river's ecology, the construction of dams on the Lower Mekong mainstream will have repercussions throughout the entire basin.

International Rivers is working with partners in the region and internationally to challenge destructive dam building and maintain the rich biodiversity and ecosystems of the Lower Mekong Basin.