Resettlement | Reservoir Area  | Multiple Benefits

RESERVOIR AREA

Current Vegetation

 The most visual impact of the Project will obviously be the inundation of 40% of the Nakai Plateau by creating a shallow reservoir (on average 7 m deep) of 450 km2 at full supply level, which will reduce to a minimum of 80 km2 at the lowest peak of the dry season. The Plateau, through which the Nam Theun River flows, is composed of agricultural land with poor quality soil, heavily degraded forest, and both permanent and seasonal wetlands. Being located on the track of the former Ho Chi Minh trail, the Nakai Plateau has been heavily bombed during the Vietnam war. There are no existing infrastructures or surfaced roads in the area to be inundated.

Reservoir Vegetation

The Plateau, through which the Nam Theun River flows, is composed of agricultural land with poor quality soil, heavily degraded forest, and both permanent and seasonal wetlands.

Biodiversity and Habitat Management

Because of the current human pressures on the Plateau, all of the species found on the Nakai Plateau and in the watershed, such as elephants, white winged ducks and various species of birds are currently under threat. The opportunities the Project will give to improve resettlers’ livelihoods and the proper protection of the watershed is expected to halt this trend, while the reservoir may develop many new habitats. On the other hand, On the basis of extensive studies regarding aquatic biodiversity, it can now be affirmed that no endemic fish species unique to the Nam Theun River have been found, and thus extinction of species will not occur because of the reservoir. However, a decrease in the number of species may occur, while some will flourish. Ultimately, it is expected that the Project will provide a net environmental benefit in terms of biodiversity conservation.

Water Quality Management

Extensive studies have been performed regarding potential sediment and water quality in the reservoir. For the first few years, the water quality in the reservoir, and therefore the water released in the downstream Xe Bang Fai River, will be governed by the decay of the trees and other organic matter in the lake. After that time, the quality will improve and sedimentation will depend on the quality of the inflowing streams. The protection of the watershed will ensure that its water runoffs will remain in its presently very good quality. The lake is also relatively shallow and it is drawn down by 10 m every year. The sun and wind effects on the water will act to keep the oxygen levels high and noxious elements such as phosphorous, ammonia and hydrogen sulphide low.

GHG Emission

It is widely acknowledge that in the long run, large reservoirs release less GHG that thermal power plants. A preliminary study shows that the future reservoir would release 15 to 20 times less GHG than a gas fired power plant of a similar size, and almost 35 times less than a coal fired power plant over a 100-year period.

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