Nam Ngum Reservoir or Nam Ngum Dam in Vientiane is a hydroelectric dam on the Nam Ngum River, a major tributary of the Mekong River in Laos. It was the first hydropower dam built in the Lao PDR.

Nam Ngum Reservoir, also known as Nam Ngum Lake, is the largest body of water in land locked Laos and it’s easily accessible on a day trip from both Vientiane and Vang Vieng.

About Nam Ngum Reservoir
Nam Ngum Reservoir was created in 1971 with the construction of dam impeding the progress of the Nam Ngum River, which is a major tributary of the Mekong. This 70 metre high and 468 metre wide dam is part of a hydro-electric project which accounts for most of the electricity produced in Laos. The project also produces excess power which is exported to Thailand raising about a quarter of the foreign currency received by the Laotian state.

About the Lake

Nam Ngum Reservoir covers an area of approximately 370 square kilometres. For this reason it is often referred to as the Lao Sea, and it does have beaches scattered along its shoreline. It also has islands. Many of these are too small to inhabit, however, the largest, Don 516, has around 500 permanent residents. There is some accommodation on the islands but most of the resorts are dotted around the coastline. Many of resorts are very basic, with the major exception of the Dansavanh Nam Ngum Resort which has a golf course and 24 hour casino. This resort is popular with senior government officials from both Laos and Thailand.

Public services from Vientiane to Thalat, which is near Nam Ngum Reservoir, depart from both Vientiane Central Bus Station and Vientiane Northern Bus Terminal. The fare to Thalat is around 25,000 Lao Kip. From Thalat you need to take a tuk-tuk to the lakeside which should cost you a further 20,000 Lao Kip. The closet part of the lake to Thalat is the small village of Na Num, which is close to the dam. The dam has a viewing platform and is worth going to see. At the lakeside there are some water front restaurants on stilts and some floating restaurants. A popular activity is take a boat trip out onto the lake. The boats themselves tend to be quite large with seating for around 20 people. If you go alone expect to pay around 150,000 Lao Kip for a 2 hours trip. If you search out a local with a smaller boat then the charge can be considerably less.

Minivans and buses travelling from Vang Vieng to Vientane all pass through the town of Tha Heua. Tha Heua is on the edge of the lake so you simply need to be asked to be dropped off there on route to Vientiane. Tha Heua is less popular than Na Num but also has waterside restaurants and boats to hire for trips out on the lake. The journey by boat from Tha Heua to Na Num takes about 5 hours, after which you could continue your journey to Vientiane by local bus. Tha Heua also has the relatively luxurious Sanctuary Nam Ngum Beach Resort which doesn’t have a casino full of Thai and Lao Government officials, but does have a beach which you can swim off as well as a swimming pool if you prefer to swim in cleaner water.

Environmental concerns

The project, like most dam projects, also caused widespread ecological damage and displaced large numbers of people. A large area of forest was submerged, the size and variety of fish in the Nan Ngum River as a whole has diminished, and there are growing concerns about whether the river can supply sufficient water for irrigation for local agriculture and maintain the water levels required to keep the electric generating turbines working at a sufficient rate to keep up with the demand for power.