Nam Ngum Dam

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Nam Ngum Dam
Nam Ngum Dam is located in Laos
Nam Ngum Dam
Location of Nam Ngum Dam
Location Vientiane Capital, Laos
Coordinates 18°31′51″N 102°32′51″E / 18.53083°N 102.54750°E / 18.53083; 102.54750Coordinates: 18°31′51″N 102°32′51″E / 18.53083°N 102.54750°E / 18.53083; 102.54750
Construction began 1968
Opening date 1971
Construction cost US$97 million (over three phases)
Owner(s) EDL
Dam and spillways
Type of dam Gravity dam
Impounds Nam Ngum River
Height 70 m (230 ft)
Length 468 m (1,535 ft)
Spillway type Radial
Creates Ang Nam Ngum
Total capacity 4.7 km3 (3,800,000 acre·ft)
Catchment area 8,460 km2 (3,266 sq mi)
Surface area 370 km2 (140 sq mi)
Power station
Operator(s) EDL-GEN
Commission date 1971
Hydraulic head 45.5m
Turbines 2 x 17.5 MW Francis
3 x 40 MW Francis
Installed capacity 155 MW
Annual generation 865 GW

The Nam Ngum Dam is a hydroelectric dam on the Nam Ngum river, a major tributary of the Mekong in Laos. It is the oldest dam in Laos, and its reservoir is the largest water body in the country.


The dam is approx. 90 km north of Vientiane, the capital of Laos, within the Vientiane Capital Province. Its reservoir covers 370 km2 (140 sq mi), and is the largest water body in Laos. The Nam Ngum catchment covers 8,460 km2 (3,266 sq mi), and is on track to becoming one of the most heavily dammed catchments in Laos, with six additional dams at various stages of planning and construction, and two water diversions.


The dam was a product of the Committee for Coordination on the Lower Mekong Basin, otherwise known as the Mekong Committee, the predecessor to today's Mekong River Commission. Its development trajectory was similar to many of the dams developed in northeastern Thailand during this time, part and parcel of US Government efforts to inject development into the Mekong Region, and dissuade impoverished countries from embracing communism. Nevertheless, the dam was constructed during a time of very significant political turmoil in Laos, which eventually resulted in the overthrow of the US-backed royalist government, and the coming to power of a communist government.

The dam was developed in three phases:

Phase 1[edit]

This phase started in 1968 and ended in 1971, and yielded the concrete gravity dam and the power house, which is located at the base of the dam wall. This phase cost US$28 million with contributions from the US (almost 50% of budget), Thailand, Japan, the Netherlands and others. At this time, two 15 MW Francis turbines were installed, with provisions made for three more. A single circuit 115 KV high voltage transmission line was also installed, linking the dam to the capital, Vientiane, and thereon to Thailand.

Phase 2[edit]

This phase started in 1976, and cost US$49 million. This phase involved the installation of the spillway gates, new penstock and intake gates, and civil work to expand the powerhouse to accommodate three new generating units of 40 MW each (although only two were installed) and auxiliaries, and a double circuit 115 KV high voltage transmission line to Vientiane.

Phase 3[edit]

This phase cost US$20 million, and involved the installation of the final 40 MW Francis turbine.

In 1996, a diversion was built across the Nam Song River to channel additional water into the Nam Ngum Reservoir.

Most of the dam's electricity is intended for the domestic market, although, from time to time, electricity sourced from the Nam Ngum Dam will be exported to Thailand. This contrasts with most of Laos's other dams, electricity from which is intended mainly for export (to Thailand and Vietnam, and most of which are owned and operated by Independent Power Producers (IPPs).