China says the dams are necessary for the economic upliftment of the impoverished provinces that form part of the upper Mekong watershed. However, critics of the development plan have argued that China is ignoring the effects the dams may have on farms, fisheries and tourism in the five other countries – Vietnam, Thailand, Laos, Cambodia and Burma – that share the waters of the Mekong.

Critics and environmental groups have charged that the proposed dams will block migration routes of rare fish species such as the giant freshwater catfish, which can weigh up to 650 pounds. They say that the dams could also slow the river’s flow, raising water temperatures and possibly wiping out native fish species.

The 100m high Dachaoshan dam currently under construction in China’s southwestern Yunnan province is one of the eight dams included in China’s plan for the Mekong. The US$600M concrete structure is the second of two dams that China has already undertaken. The first, at Manwan, was finished in 1993.

Plans are afoot to begin work on the US$4B Xiaowan dam next year, said to become the tallest dam in the world.