Photos posted on the Facebook page of ABC Laos News showed dozens of Laotian people stranded on the roofs of their houses and other buildings while others were shown being evacuated by boat.
The flooding took place around 8pm, the same day XePian XeNamnoy Power Company (PNPC), that constructed XePian dam, issued a warning of the possibility that water could overflow the dam.
In a the warning letter from the company’s head of resettlement, Lee Kan Yeol told his colleagues in Champasak and Attapeu provinces that “the saddle dam D was not safe and was in a very dangerous condition” due to heavy rainfall.
“If the section fails, over five thousand million tonnes of water would flow out and down the Xe Pian river,” read the letter.
Lee said the villagers living near the XePian River downstream from the dam should move to higher land to avoid “the unfortunate accident” caused by the heavy downpours.
Rescue teams in Laos were on Tuesday working to rescue those affected by the flooding.
According to Hydroworld website, XePian Dam is one of three being constructed under the XeNamnoy hydroelectric power project along the Mekong River in Attapeu and Champasak provinces near the border with Thailand.
It is about 80 kilometres east of Pakse on the Mekong River and 35km northwest of Attapeu, (and approximately 550km southeast of Vientiane, the capital city of Laos), in the country’s southern region.
The two other dams under construction under the project are XeNamnoy Dam and Houay Makchan Dam.
XePian and XeNamnoy are rockfill dams located on the Bolaven plateau, along with saddle dams and Houay Makchan Dam. The powerhouse will be located at the plateau base, giving the scheme a head of more than 630 metres. Water will be discharged to the Xe Kong River.
The feasibility study for the project was completed in November 2008, construction began in February 2013 and commercial operations are expected to begin in 2019.
The scheme will also have a storage reservoir on the Xe Namnoy River, underground tunnels, shaft waterways, and a powerhouse that features three Francis and one Pelton turbine.
PNPC is a joint venture formed in March 2012 by SK Engineering and Construction, Korea Western Power, Ratchaburi Electricity Generating Holding, and Lao Holding State Enterprise.