For millennia the Mekong River has been the lifeblood of Laos. As the region's primary artery, about 50 million people depend on resources from the river and its tributaries. The Mekong is the world's 12th-longest river and 10th-largest in terms of volume. But unlike other major rivers, a series of rapids have prevented it from developing into a major transport and cargo thoroughfare, or as a base for large industrial cities.

Except in China, the Mekong itself is not dammed. However the greater river system has long been seen as a potentially lucrative source of hydroelectricity. And with the regional demand for power rising rapidly, plans to turn Laos into the 'battery of Southeast Asia' have been revived after a decade of stagnation.

For a country as poor as Laos there are definite benefits. Selling electricity to Thailand, Vietnam, Cambodia and China will bring much-needed foreign exchange to the economy. In theory, this windfall can be spent on developing the country while at the same time reducing its reliance on foreign aid and loans. It's an attractive proposition, and one that the Laos government and several international agencies seem happy to pursue.

The first, and biggest, cab off the rank will be the Nam Theun 2 dam in Khammuan Province, due to be finished in 2010. This controversial hydropower project was 10 years in the planning, and as such is probably one of the most studied dam projects in history. Dozens of research projects were carried out because the dam needed World Bank approval before investors would commit, and the World Bank was under sustained pressure to reduce the negative impacts as much as possible.

However, not all projects are as big or get as much publicity as Nam Theun 2. When the World Bank finally approved the project in 2005, it was the equivalent of opening hydropower's Pandora's Box. In the ensuing period a flurry of agreements has been signed between the Laos’s government and private developers, all looking for a slice of the hydropower pie. At the time of writing more than 20 hydropower projects were either being built or were in the advanced stages of planning in Laos, raising the question of whether the government has gone 'dam' crazy.

For critics, including the International Rivers Network (IRN), the answer is a resounding yes.

They claim that these lower profile dams have potentially far greater environmental and social impacts because there is no transparency and they are much harder to monitor. Although the government requires full environmental impact assessments for all hydropower schemes, if they have been carried out, few have been released to the public.

The negative impacts associated with dams include both the obvious and more difficult to see. Obvious effects include displacement of local communities, flooding upstream areas, reduced. Sediment flows and increased erosion downstream with resulting issues for fish stocks and the; fisherman who work the rivers. Less immediately visible, but with a potentially much greater j influence in the long term, are the changes these dams will have on the Mekong's flood pulse, ' which is critical to the fish spawning cycle, and thus the food source of millions of people.

All up this is a hugely complex issue. For more information, visit these websites: Asian Development Bank (www.adb.org) ",   International Rivers Network (www.irn.org) j   Laos Energy lobby (www.poweringprogress.org) Mekong River Commission (www.mrc.org) WWF