WATER TRANSFER

The Project is a water transfer scheme, meaning that it will store the Nam Theun water in a reservoir to be created on the Nakai Plateau and release water into the Xe Bang Fai River that is situated in the downstream plains at an altitude roughly 350 meters lower than the Plateau.

The increased water flows coming from the Nam Theun reservoir through the downstream channel will result in the Xe Bang Fai River modifying progressively its geomorphology and ecosystems. It will have both positive and negative impacts. While having the positive effect of improving navigation and irrigation on the river, the increased flows will result in the river adjusting its morphological equilibrium. This phenomenon will be observed along roughly 150 km from just upstream of the Nam Phit junction, with the impact being diluted while going downstream. It will affect approximately 40,000 persons or 7,000 households in 89 villages.

Downstream Survey Map Download Zip File (480 ko) December 16, 2004 - Downstream Compensation Framework (1,1Mo)

From the power plant to the Xe Bang Fai, the routing of the 27 km artificial downstream channel has been designed to minimize as much as possible the impact of it on the people livelihoods, and to avoid to the greatest extent possible, the existing paddy fields in the Gnommalat Plain. In order to limit the risk of releasing anoxic water being released during the early years of operation as a result of biomass degradation in the reservoir, NTPC has designed aeration structures in both the regulating dam and downstream channel.

From the beginning of commercial operations, an average of 220 m3/s to 330 m3/s will be added to current river flows of 20 m3/s in the dry season and 2,000 m3/s in the flood season. Water will enter the Xe Bang Fai at the Nam Phit confluence. The Nam Phit is a small stream that will be enlarged when merged with the downstream channel. To limit the erosion factor, NTPC will construct a regulating pond to minimize fluctuations in daily discharge, and has designed the downstream channel in such a way to recharge the released water with sediment. Nevertheless, it is likely that the river will widen by several meters in its early stretches below downstream channel junction.

The Project is committed to provide timely compensation for any negative livelihood impacts resulting from the increased water flows. There is also a commitment to shutdown operation before natural over bank flooding occurs, so that the Project does not exacerbate natural floods.