The break of the Xe Pian-Xe Nam Noy hydropower dam in Laos' Attapeu province on July 23 is expected to have insignificant impact on Vietnam's downstrem Mekong Delta, the Vietnamese Ministry of Natural Resources and Environment (MONRE) has said in a statement in the evening of July 25.
The Xe Pian-Xe Nam Noy hydropower dam collapsed in Attapeu province, Laos. Photo: Internet
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The Xe Pian-Xe Nam Noy hydropower dam is a key project for hydropower development in southern Laos, located on the Xenamnoy River in Champasac and Attapeu provinces. The site is about 200km far from the Mekong River’s mainstream in Cambodia and 650km far from Vietnam’s border.
Work on the hydropower plant started in 2013 and was completed in early 2018 with total investment of US$1.2 billion. The reservoir has a capacity of 1.1 billion cubic meters and the plant has a capacity of 410MW. When the project was 90% complete, the Xe Pian-Xe Nam Noy reservoir began to store water in early 2018. Before the collapse, the reservoir had about 500 million cubic meters (m3).
Before the dam incident occurred, the water level at Stung Treng station (200km far from the Mekong mainstream in Cambodia) measured at 7:00pm on July 23 was 9.0m (equivalent to a flow of 35,700m3). At 7:00am on July 24, the leval was measured at 9.35m, to 7:00am on July 25 at 9.6m (equivalent to 39.900m3).
Thus, after 36h the water level at Stung Treng station increased by 0.6m. If the current trend continues, the water level at Stung Treng station increases on average about 20 - 30cm per day.
"Until now, the impact of the dam incident on Stung Treng station’s water level is negligible," the ministry noted.
In the next four to five days, the amount of water released by the dam break will affect the flow of the Mekong River into Vietnam. The uptream water level of the Mekong River is calculated to increase by a maximum of 5-10cm.
In the days ahead, the water level of the Mekong River will rise rapidly due to floods and high tides. On July 31, the highest water level on the Tien River at Tan Chau station is likely to reach 3.2m (0.3m lower than warning level 1); on the Hau River at Chau Doc Station ilikely at 2.6m (0.4m lower than warning level 1).
Vietnam has three grades of warning for water levels at its rivers, from level 1, the lowest, to level 3, the highest.
"Therefore, preliminary estimates show that the collapse of the Xe Pian-Xe Nam Noy dam will have a minor impact on Vietnam's Mekong Delta region," the Vietnamese ministry stressed.
