Nam Ngum Dam
|This article does not cite any references or sources. (February 2013)|
|Nam Ngum Dam|
|Location||Vientiane Capital, Laos|
|Construction cost||US$97 million (over three phases)|
|Dam and spillways|
|Type of dam||Gravity dam|
|Height||70 m (230 ft)|
|Length||468 m (1,535 ft)|
|Impounds||Nam Ngum River|
|Type of spillway||Radial|
|Creates||Ang Nam Ngum|
|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)|
|Turbines||2 x 17.5 MW Francis
3 x 40 MW Francis
|Installed capacity||155 MW|
|Annual generation||865 GW|
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:
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.
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.
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).