Risk of lake burst near China-Nepal disaster site wanes

The threat of a lake formed after a glacier collapse bursting near the China-Nepal ‌border, where a devastating flood struck earlier this week, has eased, Chinese authorities said today (29 August) , as it appears to have shrunk.

By Saturday afternoon, ​parts of the lake bed had become visible, CCTV reported.

The ministry said satellite imagery of the lake on the Purepu Tsangpo river showed it covered 99,000 square ​metres (1.1 million square feet) early on Saturday, roughly the size of 14 soccer pitches, having shrunk by 21,000 square metres since Thursday.

A glacier collapse ⁠on Wednesday sent a torrent of rock, ice, mud and debris through Himalayan river systems, sweeping away a border port complex linking Tibet with Nepal, killing hundreds and leaving thousands ​missing.

Risks under watch

Experts and authorities have warned of an extremely high risk of secondary disasters in the valley, particularly from the lake formed by glacier debris, which could threaten 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 company China Anneng, which has been monitoring ​the lake since Thursday, has deployed radar and drones around the lake for 24-hour surveillance, CCTV said.

Initial overflow from the lake on Friday temporarily halted rescue work before a subsequent assessment ​deemed the risks manageable.

Authorities have also flagged another, larger body of water at the foot of the glacier collapse.

"We estimate its area to be over 120,000 square metres, 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 both lakes have fully drained, an official with Nepal's Disaster Management Authority has said.

Looking for survivors

In bleak, rainy conditions on Saturday morning, more than 50 rescue workers combed through rubble of boulders and mud, looking for signs of life and calling out for survivors, CCTV reported.

The first rescue team and a search dog reached the Gyirong border crossing complex on Friday afternoon and found it reduced to ruins.

Dangerous conditions at the main disaster zone, compounded by damaged ​roads and disrupted communications, continue to hamper ​Chinese relief efforts, state news agency Xinhua ⁠said.

Forecasts show intermittent rain in the area over the next three days.

Authorities are racing to reopen a key highway leading to the border port. By Saturday afternoon, crews had advanced within about 1.5 km (0.93 mile) of the site.

China's death toll rose to seven early on Saturday, ​with 554 people still missing.

Nearly 500 villagers and construction workers, along with 555 tourists in the area, have been evacuated, Xinhua said.

Cause ​still unclear

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.