Nam Theun 1 Dam Hydropower Info by Hobo Maps - Go to Hydropower Projects Page - - Home
The Nam Theun 1 project is located on the Nam Kading (river) about 33 km upstream from where the Nam Kading joins the Mekong near Pak Kading town on the border between Bolikhamxai and Khammouane Provinces.
Nam Theun 1 is pronounced like "Nam Tehn Noong".
Nam Theun 1 location is shown in satellite image below at coordinates 18°21'25.2"N 104°08'52.8"E (18.357, 104.148):
The project is being developed by Nam Theun 1 Power Company, a joint venture of Phonesack Group (PSG 32%), Chaleun Sekong Energy Company (CSE 28%), Electricity Generating Public Company of Thailand (EGCO 25%), and Electricite Du Laos (EDL GEN 15%).
Project cost is estimated at US$ 1,335 million with major financing provided by Bangkok Bank, Export-Import Bank of Thailand, Siam Commercial Bank and TISCO Bank.
Nam Theun 1 hydropower project images below:
The project will operate as Build-Operate-Transfer (BOT) type with a concession period of 27 years.
The project is designed for hydro-peaking with 80% of 650 MW output (520 MW) going to Electricity Generating Authority of Thailand (EGAT) and 20% (130 MW) to Electricité du Laos (EDL).
Construction of the project started in 2017, the reservoir impounding began in June 2021 and full operation and commissioning was in August 2022.
Nam Theun 1 reservoir image below:
The 650 MW project can generate up to 2,638 GWh output per year. The project has a 27-year power purchase agreement with EGAT having Thai export offtake of 514 MW capacity and with Electricité du Laos (EDL) for 130 MW.
The main dam structure is a 177-meter-high curved-gravity Rolled Compressed Concrete (RCC) dam with a gated crest spillway.
The powerhouse is located on the left bank of the river 450 meters downstream from the dam structure and has 3 vertical axis Francis turbine-generator units (2x260 MW for EGAT and 1x130 MW for EDL).
Facebook video created July 2022 during commissioning exercises HERE .
Nam Theun 1 site image below:
A diversion tunnel located on the right bank will allow dry season floods of the Nam Kading to pass safely. Allowance is also made for safe overflow during the rainy season of the main dam and the two cofferdams.
An intake structure located above the dam takes water down a headrace tunnel (11 meters in diameter) to the powerhouse. The bifurcated headrace tunnel is a reinforced concrete lining type with 565 meters length for the EDL Shaft and 544 meters length for the EGAT Shaft.
Full reservoir capacity is about 3 billion cubic meters with 2 billion of that as active storage. Normal reservoir water surface level is 292 meters above mean sea level.
The project also involved the construction of two cofferdams.
The Nam Theun 1 hydroelectric power plant operates with a head of about 140 meters.
The project involves a diversion channel, a headrace tunnel connected to a 10 meter-diameter steel penstock, a spillway and a tailrace channel.
Nam Theun 1 Hydropower Project Details below:
The Nam Theun 1 reservoir gets its water from the very large and wet 14,000 square km Nam Theun-Nam Kading catchment basin. Both the Nam Theun 2 Hydropower Project and the Theun-Hinboun Hydropower Project further upstream on the Nam Theun river divert water out from this basin into another basin which in effect decreases the flow that otherwise would have come into the Nam Theun 1 reservoir resulting in less available for power generation by Nam Theun 1.
See our Map of area's basins and drainage .
Map below shows Nam Theun 1 Dam Hydropower project in upper left near Pak Kading:
Contractors of the Nam Theun 1 hydropower project
Italian-based Cooperativa Muratori e Cementisti (CMC) together with Italian-Thai Development Public Company and Vietnamese state-owned Song Da Corporation were contracted for civil and hydro-mechanical works of the project.
Song Da Corporation’s work included blasting, excavation and transportation of soil and rock as well as construction of the crushing and batching plant and the cofferdams for the project.
Italian-based ATB Riva Calzoni supplied the penstocks, bottom outlet and other hydro-mechanical equipment.
China’s state-owned Sinohydro Bureau 3 was engaged in civil works for the project.
Vienna-based Andritz Hydro provided the design, manufacture and supply of electromechanical equipment. This includes three vertical Francis turbines with a total output of around 650 megawatts, model test, generators, governors, automation system, main transformer, medium- and low-voltage switchgears, power and control cables, fire protection system, 500kV GIS (Gas Insulated Switchgear), the main inlet valve, mechanical auxiliaries, installation supervision and commissioning..
Pöyry (now Afry) was engaged as the owner’s engineer.
Italian-based Simen provided the concrete batching plant while NMS Industries provided the sand and gravel processing system.
Thai-based Right Tunneling handled the underground excavation and concrete lining works for the project.
Nam Theun 1 images below during tests for commissioning July 2022
Nam Theun 1 construction in progress images below:
Project history below from CS Energy website Nov. 2021:
Nam Theun is pronounced like "Nam tune".
During commissioning work in July 2022 some water leakage was seen coming from a natural rock formation next to the concrete dam structure. The project developer and owner has assured the public that there is no imminent risk of dam failure or need to worry.
Name Confusion - Why not Nam Kading HPP?
Nam Theun 1 (NT1) hydropower project has a confusing name since the project is neither on or near the Nam Theun river. The Nam Theun 1 project is actually located on the Nam Kading river near Pak Kading town on the Mekong. Nam Kading river at some time in the past may have been called the Nam Theun or maybe it is the same river with a simple name change near the Theun-Hinboun head pond.
Nam Theun 1 hydropower project also has no connection with the Nam Theun 2 (NT2) hydropower project either geographically or by ownership. NT2 was actually created first and has been operating since 2010. Water from the Nam Theun river does flow into the Nakai reservoir that powers the NT2 project but outflows from the NT2 powerhouse now are diverted into a different drainage basin and no longer flow into the Nam Theun river that ends up as a tributary of the Nam Kading.
The Nam Theun river may also be a major tributary of the Nam Kading river that merges near the Theun-Hinboun hydropower project.
Nam Theun 1 switchyard image below:
The electrical transmission infrastructure at the project site includes transformers, low and medium-voltage switchgears and a 500 kV gas-insulated substation (GIS).
For EDL offtake, a 115 KV transmission line will take power 9 km to the Paksan-Khonsong substation. For EGAT offtake, a 500 KV transmission line takes power 154 km to Nabong substation in Laos for re-transmission to Thailand as seen in map below. See enlarged version HERE
