Remarkably little international attention has been given to the beginning of work on the Lower Se San 2 dam in Cambodia, a major hydroelectric dam on one of the Mekong's main tributaries which plays a key part in the annual breeding cycle of the river's fish, which are a major contributor to the Cambodian population's protein intake. One of the rare exceptions is this new report from Deutsche Welle.

The dam, which is being built by a consortium of the Cambodian Royal Group and Hydrolancang International Energy of China, is projected to cost US$781 million and to produce 370 MW of electricity.

While the Cambodian Government has claimed that the dam will not have an effect on the Mekong's fish stocks, as I previous reported in The Interpreter, a major study published in the Proceedings of the National Academy of Sciences in the US and reported in Nature disputes this view, with the estimate the new dam will result in a diminishing of the annual fish catch in the Mekong of more than 9%. More immediately, it is estimated that the dam will result in the displacement of villagers and their access to traditional fishing grounds.

Separately, but again involving Chinese dam-building efforts, there are once again indications that Beijing is giving serious consideration to the construction of dams on the upper reaches of the Salween River (or the Nu Jiang, 'Angry River') in Yunnan province, and that some preliminary construction is taking place.

This issue of dams on the upper Salween was examined in depth in my Lowy 'Perspectives' paper, The Water Politics of China and Southeast Asia II: Rivers, Dams, Cargo Boats and the Environment, in May 2007. At that time it seemed possible that domestic opposition to the proposed dams, which would be located in a particularly rich biodiversity region, including from the Chinese Academy of the Sciences, would prevent construction.

More generally, there is concern among neighbours that China's control of Tibet, where rivers such as the Mekong and the Salween rise, means that Beijing will ultimately be in a position to determine how much water reaches its downstream neighbours. For the moment this may be an alarmist view, but it is notable that China has not signed the UN water sharing treaty that would be applicable to all the transnational rivers that flow out of its territory.

Photo by Flickr user Akuppa.