Main features of the Nam Theun 2 hydroelectric project (Lao PDR) and the associated environmental monitoring programmes

The Nam Theun 2 hydroelectric Project is located in Lao PDR on the Nam Theun River. The reservoir impoundment started in April 2008 and hydropower generation began in March 2010. The reservoir has a total volume of 3.9 billion m3, covering an area of 489 km2 at full supply level and 86 km2 at the minimum operating level. The performance is 1070 MW and the annual production is 6 TWh. The reservoir is operated seasonally by storing water during the wet season. A system of tunnels and channels diverts the waters from the Nam Theun watershed to the Xe Bangfai watershed. An ambitious environmental monitoring programme of project sites was launched by EDF - NTPC in 2008 and remains operational. An on-site laboratory was established to ensure sampling and analysis in real time. The compartments studied are water quality, greenhouse gas emissions, phytoplankton, zooplankton, benthic macroinvertebrates and fish. A 3D numerical model was developed based on monitoring data to predict the long-term changes in water quality and greenhouse gas production of the reservoir. Additional research programmes have been launched to understand bio-chemical dynamics and processes.