Nam Mang 3 Hydro Power Plant     There have been 2470 visitors to this websiteThere have been 2470 visitors to this websiteThere have been 2470 visitors to this websiteThere have been 2470 visitors to this website 

  • Environmental Impact Assessment (EIA)    


Location: Namyam Village, Thulakhom district, Vientiane Province

Tel : 023 380223

Fax: 023 380228


Nam Mang 3 Hydropower Plant is a multi-purpose project. It does not only provide electricity, it is also helpful regarding water irrigation. Nam Mang 3 Hydropower Plant is located at Phou Khao Khouay Mountain, 60 km north of Vientiane Capital City, 15 km south west of Nam Leuk Hydropower Plant. Nam Mang 3 Hydropower Plant is a run-of-river scheme. The water from Nam Yong

River (750 masl) which is one of the Nam Mang River’s tributaries comes from a point substantially higher than the reservoir (200 masl). The 550 m of height difference is able to provide a hydropower potential up to 40 MW, with an average energy production of 138 to 140 GWh/year.

The preliminary feasibility study in 1992, proposed a bigger reservoir which would included the reservoir from another dam with an installed capacity of 35 MW. In 1994, another feasibility study, which had more information regarding the geographic of Lao PDR proposed various options. However, the conclusion from the feasibility study in 2001, which considered more thoroughly environmental impacts, was a proposal for a smaller reservoir and only one dam with a height of 28 m,

located near the confluence of the Nam Yong River with the Nam Mang River. The proposed dam has a the catchment area of 68 km2 and the water is diverted from Huay Kwang, which is a branch of Nam Yong River, through a water intake, tunnel and penstock, to Nam Mang 3 reservoir, which has a catchment area of 14 km2, reservoir area (full supply level) of 10.2 km2, average discharge of 4.19 m3/ sand total discharge of 132 km3/year.

Nam Mang 3 Hydropower Plant construction is divided into 2 phases. The total construction cost of the first phase is USD 63 million and the second phase is USD 27 million. In both phases, 80 percent of the fund came from a loan from the Export-Import Bank of China and the other 20 percent came from EDL.

Main features of the project

1. Storage

Catchment area

Full water level

Low water level

Storage capacity

Active storage

Reservoir area (full supply level)

2. Dam




Reservoir level

Over spillway

3. Saddle Dam


Reservoir level


4. Operation Discharge System: Tunnel




Headrace tunnel diameter

Headrace tunnel length

Maximum operation discharge

Power station rated output     


68 km2

750 masl

742 masl

59 x 106 m3

44.5 x 106 m3

10.20 km2

reinforced cement concrete

28 m

150.93 m

754 masl

1,030 m3/s

19.9 m

755 masl

435.8 m


1.8 x 2.2 m

512 m

0.95 – 1.8 m

3,152 m

9.14 m3/s

40 MW