Collapse of dam is feared to have killed over a hundred in southern Laos.

Twenty six people have now been confirmed dead and over 130 more are still missing following the collapse of a dam at a hydro-electric plant in southern Laos on Monday 23 July 2018. The incident happened at about 8.00 pm local time, when the Xepian Xe Nam Noy Dam, part of a hydroelectric plant being constructed on the Mekong River in Attapeu Province gave way with very little warning, releasing about five billion cubic metres of water in a wave that was about 10 m high when it hit the closest villages. At least six villages were hit by the flood, with around 6000 people being forced to flee their homes, and a similar number suffering flood damage to varying degrees.

Flooding in Attapeu Province, Laos, following the collapse of a dam at the Xepian Xe Nam Noy Hydroelectric Projest. AFP/Getty Images.

The hydroelectric project, which is estimated to have been about 90% complete at the time of its collapse, was being constructed by a consortium of Thai and South Korean companies, ostensibly to bring power to rural regions of what is one of Asia's least developed nations, though it is likely that most of the electricity generated would have been exported to Thailand. The dam is thought to have collapsed due to an unexpectedly high volume of water gathering behind it due to this year's exceptional monsoon season. It is also feared that, in addition to the obvious damage caused by the flood, the sudden release of water may have scoured away river beds and topsoil, exposing unexploded bombs dropped in the area by the US during the Vietnam War.

Villagers sheltering on the roofs of their homes following a flood triggered by the collapse of a dam in Attapeu Province, Laos, on 23 July 2018. Reuters.

Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate.

 Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.

Much of Southeast Asia has two distinct Monsoon Seasons, with a Northeast Monsoon driven by winds from  the South China Sea that lasts from November to February and a Southwest Monsoon driven by winds from the southern Indian Ocean from March to October. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest.  

The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.

  

See also...

Follow Sciency Thoughts on Facebook.

A new species of Tailorbird from the Mekong floodplain of Cambodia.

Tailorbirds of the genus Orthotomus are small Warblers that get their name from their method of building nests, which involves stitching the sides of a large leaf together with plant fibers or Spider silk to form a cradle, within which a woven grass nest is constructed. Unlike most Warblers, Tailorbirds are often brightly coloured. Tailorbirds are found across south and east Asia from India to the Philippines and Indonesia.

In a paper published in the journal Forktail on 25 June 2013, a team of scientists led by Simon Mahood of the Wildlife Conservation Society of Cambodia describe a new species of tailorbird from the Mekong floodplain of southern Cambodia.

The new species is named Orthotomus chaktomuk, where 'chaktomuk' is a Khmer word meaning ‘four

faces’, a reference to the confluence of the Tonle Sap, Bassac and Mekong rivers at Phnom Penh, which was formerly known as Krong Chaktomuk. It is also referred to be the English name 'Cambodian Tailorbird'.

Orthotomus chaktomuk is a 9 cm greyish Warbler with a distinctive cinnamon-brown crown. It was initially discovered during sapling of wild birds in Cambodia for avian influenza in 2009. Orthotomus chaktomuk appears to dwell close to the ground in thick evergreen scrub, between 3 and 25 m above sea-level, on the floodplains of southern Cambodia, including within Phnom Penh. It is unclear if its range extends into Vietnam.

Orthotomus chaktomuk, the Cambodian Tailorbird. Mahood et al. (2013).

Because much of the natural habitat of Orthotomus chaktomuk is under threat from expanding rice cultivation, Mahood et al. recomend that it should be classified as Near Threatened on the IUCN Red List. 

Orthotomus chaktomuk appears to be very closely related to another Tailorbird found in the region, Orthotomus atrogularis, the Dark-necked Tailorbird, which is widespread across south and east Asia. Mahood et al. suggest that on the grounds of morphological and genetic analysis alone the two birds would probably be classified as subspecies. However the two species appeared to live alongside one-another without interbreeding, suggesting that behavioral boundaries exist which keep the two birds separate, and which therefore justify the description of Orthotomus chaktomuk as a full species.

See also A fossil Vulture from the Miocene of Nebraska, A new Long-tailed Bird from the Early Cretaceous of China, How Bar-headed Geese cross the Himalayas, A fossil Bird from the Eocene of Guangdong Province China and The impact of the introduced Common Myna on the Birds of Canberra.

Follow Sciency Thoughts on Facebook.