Risk of lake bursting near China-Nepal border disaster site wanes
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A drone view shows a barrier lake formed following a mudslide, in the border area between Tibet, China and Nepal on Aug 27.
PHOTO: REUTERS
BEIJING - The threat of a lake - formed after a glacier collapse - bursting near the China-Nepal border where a devastating flood occurred earlier this week has decreased, Chinese authorities said on Aug 29, as its size appears to have shrunk.
Satellite images from Aug 27 to the morning of Aug 29 suggest that water in the lake – straddling the China-Nepal border at the confluence of two rivers – has been slowly flowing through, decreasing the reservoir gradually, state broadcaster CCTV reported citing the Water Resources Ministry.
By Aug 29, parts of the lake bed had become visible, CCTV reported.
The ministry said satellite imagery of the surface area of the lake at Purepu Tsangpo river showed it was 99,000 sq m in size on early on the morning of Aug 29 – around the size of 14 football fields combined – having shrunk by 21,000 sq m compared with images from Aug 27.
A glacier collapse on Aug 26, which sent a powerful torrent of rock, ice, mud and debris through Himalayan mountain river systems and swept away a border port complex linking China's Tibet to Nepal, killed hundreds and left thousands missing.
Experts and the authorities have warned of the extremely high risk of secondary disasters in the valley, especially from the lake that was formed by glacier debris, potentially endangering rescue operations downstream.
With water draining naturally, Water Resources Ministry experts said search and rescue operations downstream could continue safely if outflows remain low or manageable and recede completely within two to three days.
Rescue workers could be notified promptly to evacuate if any abnormalities appear at the lake, with warnings issued more than 30 minutes in advance, CCTV cited the experts as saying.
State-owned engineering and rescue enterprise China Anneng, which has been monitoring the lake since Aug 27, dispatched a 15-member team on Aug 28 with reconnaissance drones, portable satellite stations and mobile surveillance cameras to gather more data about the lake.
An overflow from the lake on Aug 28 temporarily halted rescue work before further assessment deemed the risks manageable.
Authorities have also flagged another larger body of water at the bottom of the glacier collapse.
“We estimate its area to be over 120,000 sq m, but its depth is currently unknown,” said Chen Hongqi, a senior engineer at the Ministry of Natural Resources’ Geological Disaster Technical Guidance Center.
Flood risks will remain until the two lakes have fully drained, an official with Nepal’s Disaster Management Authority has said.
In bleak rainy weather on the morning of Aug 29, more than 50 rescue workers combed through the grey rubble of boulders and mud looking for signs of life and calling out to any survivors, according to CCTV.
The first team of rescuers and a search-and-rescue dog had made their way to the location of the Gyirong border crossing complex on the afternoon of Aug 28, which they described as having nothing left but ruins.
Dangerous conditions at the main disaster zone, made more complex as roads and communication were cut off, continue to pose challenges to the Chinese relief efforts, state news agency Xinhua said.
China’s death count from the disaster rose to seven early on Aug 29, with 554 still missing.
Nearly 500 villagers and construction workers, as well as all 555 tourists from the area have been evacuated, Chinese state-run news agency Xinhua said.
The cause of the collapse remains unclear, but climate experts say global warming could be a factor.
“We’re still not absolutely sure whether it was triggered by an earthquake or ... by warm temperatures melting the glacier,” said Benjamin Horton, dean of the School of Energy and Environment at the City University of Hong Kong.
Videos shared on social media and verified by Reuters show the lower section of the glacier near the Langtang Lirung mountain peak breaking away and plunging into the valley below, triggering an avalanche of ice and rock and a massive landslide.
“One of the reasons why we don’t fully understand the mechanisms that cause the landslide is that we have a lack of data. So there has to be this investment in the science, there has to be this investment in society,” Horton said. REUTERS
