Dam problems - Dams examples

Damming the Mekong

A river in trouble - As water levels in the Mekong started dropping alarmingly at the start of 2004, the river has made the headlines around the world.

"China drains life from Mekong river" (New Scientist), "Chinese dams blamed as Mekong river level drops" (Reuters AlertNet), "Dammed and dying" (The Guardian), "Low water blamed on China dams" (Bangkok Post). Most put the blame firmly on dams being developed in the upper reaches of the Mekong in China. But are they giving the full picture?

Dams in China ...
In 1986 China started the construction of the Manwan dam on the Lancangjiang, the Chinese name for the Mekong, the first of a cascade of 8 hydropower dams in Yunnan Province. The 126 m high dam was completed in 1996 and was followed in 2003 by the 110 m high Dachaoshan dam. There is little doubt that dams in the upper Mekong are having an impact on the downstream hydrology and ecology.

But there is still uncertainty about the nature and extent of the impacts. According to the Mekong River Commission, of which China is not a member, water levels in the middle reaches of the Mekong became more variable, with irregular changes of water levels over short periods of time. Significant reductions in sediments were also measured, stretching as far as southern Laos. Both are likely to have an impact on fish and other aquatic life in the river.

... are they to blame?
Nevertheless, it is unlikely that these 2 dams are the single direct cause of the extremely low levels observed in the first half of 2004. The low water levels are observed throughout the basin, including Cambodia and the Mekong Delta in Vietnam, where the contribution of China to the river's flow is substantially less. Rainfall during the 2003 wet season has been much lower than usual, and the river levels in many rivers in Thailand are lower than usual as well, whilst the number of forest fires has increased by 50%.

And what other impacts do they have?
But even if the Manwan and Dachaoshan dams are not directly to blame for the low water levels, this is no reason not to be concerned about the future impacts of dams in the upper Mekong (PDF: 1.40 MB). Construction is also underway at the Xiaowan dam, which is second in size only to the Three Gorges Dam. The 292 m high arch dam will span the river over nearly 900 meters and create a reservoir that backs up in the narrow gorges for 178 km. Construction is also underway at Jinghong Dam and four more large dams, one of which will have a storage capacity similar to Xiaowan.

Evidently, such large-scale construction will impact on local populations and the local environment, but the impacts will stretch beyond the border as well. And with climate change and droughts increasingly becoming a concern, there is a real need for transparency on the Upper Mekong dams and for the inclusion of the upper basin in the planning of Mekong basin management.