There is increasing concern among commentators charting the Mekong's future that the Lao Government's decision to proceed with the construction of a dam on the mainstream of the Mekong at Xayaburi could lead to other dams being constructed on the river.

While some of the evidence about plans for new dams in Laos and Cambodia is anecdotal, it appears possible that the Cambodian Government is giving serious consideration to building a major dam at Sambor, a site on the Mekong a little to the north of the provincial town of Kratie, while the Lao Government may be contemplating constructing additional Mekong mainstream dams at Pak Beng and Don Sahong.

A more immediate cause for concern by dam opponents is the Cambodian decision, announced in November last year, to approve construction of a dam on the Se San River (the Lower Se San Dam 2), a major tributary of the Mekong and a recognised spawning ground for the fish that provide so much of Cambodia's annual animal protein intake.

A major research project published in the Proceedings of the National Academy of Sciences in the US and reported in Nature in early 2012 estimated that the dam, if built, would result in a loss of more than 9% of the annual fish catch taken out of the Mekong because of the key role the Se San plays in the annual cycle of fish spawning in the Mekong.

Finance for the dam will be provided by a consortium of the Royal Group of Cambodia and China's Hydrolancang International Energy Company.

Whether Vientiane is giving serious consideration to new dams at Pak Beng and Don Sahong is much less clear, despite suggestions by environmentalists that this is the case. Radio Free Asia reported in October 2012 that a Lao official had indicated consideration was being given to constructing a dam at Pak Beng, a location in northern Laos which, like Xayaburi, has topography particularly well suited to dam construction.

As for the Don Sahong site in the far south of Laos, the NGO International Rivers has claimed that construction is taking place at this location, which has long been under consideration as a location for a mainstream dam.

As for the possibility of a dam at Sambor, it is difficult to overemphasise the threats to the Mekong's fish catches that would result. It is in the middle of one of the most important of the river's fish migratory systems and was identified as long ago as 2003 as the 'worst' location for a dam to be built on the Mekong in terms of the blockage of migratory fish.

Construction, should the dam go ahead, will be undertaken by China Southern Power Grid Company.

The inability of the Mekong River Commission (MRC) to take any action in relation to these various possible developments was once again illustrated at the MRC's meeting of 18 January. It provided an opportunity for the Cambodian and Vietnamese representative to call, once again, for Laos to reconsider its decision to construct the Xayaburi dam, but as has been the case in the past this did not bring a positive response from the Lao representatives on the Commission.

Photo by Flickr user fabiogis50.