As the Xayaburi hydropower project in Laos began its first day of electricity generation yesterday on the Mekong River's mainstream, doubts still lingered among scientists and environmentalists about the measures proposed to mitigate the negative effects of the dam on the river's complex and large ecosystems.
At the same time, parts of the river significantly are unusually low or dried up. Some locals blamed it on the dam operation's commencement. The project's main developer blamed it on the weather and a Chinese dam.
In fact, there is still lack of knowledge and understanding about the extent to which the cascade of this and 10 other dams proposed for construction on the lower Mekong, excluding its stretches in China, will alter the river's flow regime, trap sediment or block fish migration, for instance.
Since the operation of most dams built on the upper Mekong in China, where it is known as Lancang, remains a mystery to outsiders, Xayaburi is the first dam operating on the lower part and could become an open laboratory test of how destructive or sustainable Mekong hydropower dams will be.
Unlike Chinese dams, any projects proposed on the lower Mekong must be tabled for discussion among the governments of the four countries -- Thailand, Laos, Cambodia and Vietnam -- that signed the Mekong Agreement in 1995 and formed the Mekong River Commission (MRC). They cannot veto the projects but only raise concerns about negative transboundary impacts.
In the case of Xayaburi, there have been numerous concerns. A scientific study commissioned by the MRC released in 2011 indicates a wide range of potential impacts this and other dams will have on the river's unique fish migration patterns, sediment passage and flow regime. In effect, these projects could cause a decline in the number of certain fish species, trap sediment which gives nutrients for agriculture, and affect the seasonal fluctuation of water levels.
In response, the Lao government which owns the Xayaburi dam and the project developer, have promised a raft of "mitigation measures" as part of a redesign of the dam to reduce its impacts. These include installation of a "fish lift" and "fish-friendly turbines", and a redesign of the dam's entrances to attract fish into the chamber leading to the fish pass.
The redesign is also to allow for sediment flushing and to let finer sediment move through the dam, they said.
However, the MRC's review this year reveals that the project developer has not provided sufficient information on the dam's operation regime to help its experts to better assess the effectiveness of these mitigation measures. There is no need for the operator to withhold such information if the redesign is as effective as claimed.
Notwithstanding the limited information, the MRC's review manages to highlight that there are still concerns over the redesigned fish passage. It reveals that up to 80% of the incoming sediment load will be trapped for the first several years to decades of the dam's operation. It notes that nowhere in the world have these measures been tested or monitored. This is worrying.
What works and what does not work in Xayaburi's environmental impact mitigation measures can at least provide valuable lessons for the development of other planned dams, many of which are under construction or consultation. But this can only happen if the developer and the Lao government are committed to transparency and start sharing all available information with the other three countries and the public.