In an earlier update regarding the possibility that the Lao Government might go ahead with plans to build a dam on the mainstream of the Mekong I drew attention to the manner in which the Vientiane authorities continued to equivocate on their intentions.

The Lao equivocation continues but has taken on a tone more in favour of going ahead with the dam. This is despite sharp criticism from Cambodia and and Vietnam, fellow members of the Mekong River Commission, and requests by the MRC for more detailed study of the likely environmental impact of the dam, particularly on fisheries. Outside Laos there is broad agreement that a dam at Xayaburi would have a damaging effect on fish migration up and down the river between the Loei River in northern Thailand and an area above Chiang Saen close to where the borders of Thailand, Laos and Burma come together.

In an interview with the Bangkok Post on 22 July, Lao Deputy Minister for Energy and Mines Viraphonh Viravong rejected suggestions that work now taking place at the dam site meant that a final decision to construct the dam had been made: 'We have not started working on any construction on the Mekong River that is permanent.' Rather, he insisted that what was taking place was preliminary while engineers carried out surveys, including in the river bed.

Most disturbing for those concerned about the environmental impact of the dam, the deputy minister also said that his department is 'now considering measures proposed by the engineers to reduce the impact (on fisheries) — for instance by fish ladders.' The idea that fish ladders  are an answer to the blocking of fish movement in the Mekong has been widely discredited (pictured, an example of a fish ladder at the Rocky Reach Dam in Washington, US), not least because there are no salmon species in the river (the issue is discussed in detail here). The fish ladders constructed on Thailand's Pak Mun Dam on the Mun River, a major tributary of the Mekong, proved to be a dismal failure in the 1990s.

Until now the balance of probabilities seemed to be that Laos was still not ready to take a final decision to go ahead and build a dam at Xayaburi. That judgment now seems in need of adjustment. The odds in favour of the first-ever dam on the mainstream of the Mekong have shortened.

Photo by Flickr user SarekofVulcan.