China-Nepal glacial flood alert system warned of seven disasters – but missed this one

A China-Nepal early warning system has issued seven alerts for glacial and ice-avalanche risks in recent years, but it could not prevent Wednesday’s deadly cross-border disaster after a high-altitude ice-rock avalanche triggered a flash flood.

As of Friday morning, the death toll from the China-Nepal flash flood had risen to 469, with more than 1,000 people still missing. Nepal recorded 389 deaths and at least 644 missing people, while three people died and 558 remained missing on the Chinese side. The disaster engulfed the Gyirong Port border checkpoint, Tibet’s main foreign trade port with Nepal, and rescue teams faced difficulties reaching the affected area because of mud and debris.

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The debris flow hit a river in Nepal before travelling downstream to Gyirong county in China’s Tibet autonomous region. Specialists have suggested that a glacial rock collapse may have caused the disaster.

It remains unclear whether the warning system detected an abnormality before the incident or issued an alert.

System built to monitor cross-border risks

Chinese scientists and their counterparts in Nepal developed the system to monitor glacial lakes and related hazards across the Himalayan border region.

A paper published on Wednesday by the project team highlighted the monitoring network established during China’s second Qinghai-Tibet scientific expedition. It also referred to early warning systems for ice avalanches in the Sedongpu area of the Yarlung Tsangpo River and for the Cirenma Co glacial lake in the China-Nepal basin.

“Together, these systems have successfully issued seven early warnings [including one at the China-Nepal border last year],” the researchers wrote in the paper published in the peer-reviewed Journal of Glaciology and Geocryology, according to the South China Morning Post.

Avalanches leave little time to respond

A glaciologist from a research institute in Chengdu, Sichuan province, told Southern Weekly that high-altitude ice-rock avalanches release more energy and can cause greater destruction than typical glacial lake outburst floods.

Kang Shichang, a mountain hazards expert with the Chinese Academy of Sciences, said the cross-border location of the hazards made timely warnings difficult.

“In theory, detecting an ice-rock avalanche upstream could give about 20 minutes of warning. But monitoring equipment is limited at that area, and the source of the disaster is on the Nepalese side. By the time sensors pick up anything unusual, the mudslide may already be on its way,” Kang told Shanghai-based Chinese digital news outlet, The Paper.

The warning system uses satellite remote sensing, ground-based monitors and field observations. It tracks changes in glacial lake area, water levels, glacier movement and surrounding weather conditions.

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Himalayas record rising flood risk

The Tibetan Plateau and nearby areas contain more than 100,000 glaciers. Rising temperatures are accelerating glacier melt and increasing the risk of glacial lake outburst floods.

The Cirenma Co glacial lake on the China-Nepal border burst in 1981. The flood destroyed the China-Nepal Friendship Bridge and killed more than 200 people in Nepal.

Between 2011 and 2020, the region recorded more than 15 glacial lake outburst floods a year on average—three times the average recorded between 1981 and 1990.

Research from China’s second Qinghai-Tibet scientific expedition, published in 2025, identified 1,256 high-risk glacial lakes. Of these, 182 were classified as posing an extremely high risk of outburst flooding.

Earlier warning exposed gaps in system

A research team from the Chinese Academy of Sciences’ Institute of Tibetan Plateau Research began developing the cross-border warning system in 2017.

On July 7 last year, patrols along the Boqu River in Tibet’s Nyalam county noticed that the water had turned cloudy. The sign indicated a possible glacial outburst or mudslide. Authorities were informed and evacuated downstream residents.

The following day, a 0.68-square-kilometre glacial lake on the Purepu Glacier in Gyirong county ruptured. The flood triggered a cross-border mudslide that destroyed the China-Nepal Friendship Bridge, more than a kilometre of highway and four hydropower stations. At least 18 people were killed and several others were reported missing.

Xu Baiqing, deputy director of the Institute of Tibetan Plateau Research, said the lake had not been identified as a key monitoring target by the warning system.

“It also highlighted the inherent challenges of these events, which are highly sudden and can have enormous cross-border impacts, leaving downstream areas with extremely limited time to respond once an outburst begins,” Xu said, according to the South China Morning Post.

Climate change adds to vulnerability

The full cause and impact of Wednesday’s disaster have not been officially confirmed.

However, temperatures in the Himalayas are rising at more than twice the global average. Warmer conditions allow meltwater to enter cracks deep inside glaciers, weakening their structure. Existing glacial lakes are also expanding.

A study published in December by Zhang Guoqing and researchers from the Institute of Tibetan Plateau Research projected that the intensity of Himalayan glacial lake outburst floods could rise by more than 27% without intervention, the South China Morning Post reported.