Nam Pha Gnai Dam Hydropower Info by Hobo Maps - Go to Hydropower Projects Page - - Home

Nam Pha Gnai Hydropower Project is located in Long Chieng & Xaysomboun Districts, Vientiane Province, Lao PDR. It was developed by Nam Pha Gnai Hydropower Project Co., Ltd. with US $68 million investment from the DSK Group. The hydropower plant became fully operational in March 2020.

Nam Pha Gnai is pronounced like "Nam Pah Nyai".

The project is located in the Nam Ngum river basin at the convergence of the Nam Ngum, Nam Pha Noi and Nam Pha Gnai rivers. The run-of-river hydropower project has a concrete gravity dam 70 meters high, a headrace tunnel 1.25 km long , an open surface channel 5.1 km long (maybe 6.3 km), a surface penstock 280 meters long, a forebay and three Francis turbines housed in a surface powerhouse.

Nam Pha Gnai Hydropower Project is a run-of-river hydropower project downstream of the Nam Ngum 3 hydropower project. After the completion of the Nam Ngum 3 project the water flow to the Nam Pha Gnai hydropower project will be decreased significantly.

Red line in map below shows the Nam Ngum 3 HPP diversion tunnel that takes water out of the Nam Ngum river normal flow and makes it unavailable for power production at the downriver Nam Pha Gnai hydropower project.

The installed capacity of the project from horizontal Francis turbine-generator sets is 19.2 MW (7.4 MW+7.4 MW+4.4 MW). The estimated annual power supplied to the power grid is 130 GWh before year 2020 and 86 GWh per year after 2022 when the Nam Ngum 3 hydropower project will be completed and divert some water flows away from the Nam Pha Gnai facility.

It is estimated in the dry season (from Jan.to June.) that power generation will be reduced 52.7%. In the wet season (from July to Dec.), the power operation will be reduced 16.3%.

Vientiane Geometric Services was involved with development of the project providing consulting and other services for pre-feasibility studies, dam construction, tunnels, penstock, canal and reservoir capacity.

Australian-based Entura was awarded designer contracts for owner’s engineer services and detailed engineering work in 2014. To reduce excavation and concrete work Entura used an arch profile for the dam, sloped the foundation level upstream, provided a cantilever crest upstream and used an unconventional gate structure and arrangement.

Mott Macdonald was quality control consultant and AECS Engineering & Geotechnical Services Pvt. Ltd. provided management construction services for the project.

A 115 kilowatt transmission line transmits the plant's output to EDL's Thoung Khou 2 substation in Xaysomboun Province.

Nam Pha Gnai Hydropower project location is shown in satellite images below:

Satellite image below shows our best estimate of the layouts for the Nam Ngum 3 and Nam Pha Gnai hydropower projects. When the Nam Ngum 3 project goes online (in 2023?) it will divert water from the Nam Ngum river into an underground tunnel and down to its powerhouse located near the Nam Ngum river downriver from where the Nam Pha Gnai hydropower project is located. This will drastically reduce the flow from the Nam Ngum river into the Nam Pha Gnai project.

Nam Pha Gnai plant sites in satellite images below at coordinates - 18°59'36.7"N 102°49'59.4"E (18.993540, 102.833164):

Nam Pha Gnai dam & reservoir satellite image below at coordinates 19°00'38.3"N 102°52'16.7"E (19.010624, 102.871299):

Nam Pha Gnai Hydropower project site location on terrain map below.

The Project includes a fixed weir, sandtrap, intake structure, headrace canal, headrace tunnel, forebay, penstock, powerhouse and a tailrace.

Nam Pha Gnai powerhouse images below:

Nam Pha Gnai powerhouse control room images below:

Nam Pha Gnai video (Lao audio with English subtitles) HERE .

Screenshot images from video below:

Nam Pha Gnai switchyard image below:

Nam Pha Gnai facility image below:

Nam Pha Gnai Project is shown in center of map below:

Project statistics below:

DAM DIMENSION: 65m (H) x 47m (L) x 160m (W)
SPILLWAY SIZE: 90m (W)
SLUICE GATE SIZE: 10m (W) x 7m (H)
GATE TYPE: VERTICAL ROLLER GATE
INTAKE SIZE: 3.4m  (W) x 3.75 (H)
HEAD RACE TUNNEL LENGTH: 1,250m
HEAD RACE CANAL LENGTH: 5,085m, 3.4m wide x 3.75m high
FORBAY SIZE: 77m  (L) x  10.6m (W)  x 3.75m depth
PENSTOCK TYPE: BURIED, SPIRAL WELDING
PENSTOCK LENGTH: 240m
RATED HEAD: 112.14m
POWERHOUSE TYPE: OVER-GROND WITH TAILRACE 
INSTALLED CAPACITY: 19.2MW (2 x 7.4MW  + 1 X 4.4MW)
TURBINE TYPE: HORIZONTAL FRANCIS

Nam Pha Gnai Hydropower project is a clean green project qualified under the Kyoto Protocol as a greenhouse-gas-reducing project and is estimated to reduce carbon dioxide emissions by about 62,000 tons per year. This qualifies it as a Clean Development Mechanism (CDM) project and able to earn CO2 reduction credits. View or download CDM application document HERE .