China-Nepal rescue operations paused as barrier lake overflow raises flood risk

Rescue efforts along the China-Nepal border have been temporarily suspended after a newly formed barrier lake began overflowing, raising fears of additional flash floods and landslides in the disaster-stricken region. Authorities in both countries halted operations on Friday to assess the danger posed by the lake, which holds enough water to fill an estimated 1,000 Olympic swimming pools.

The lake formed after a powerful landslide and torrential flooding devastated the area on Wednesday, damming up a river with debris. Chinese state broadcaster CCTV reported that the lake has begun overflowing continuously, making it too dangerous for rescue teams to proceed to the hard-hit Gyirong border port, a critical disaster zone.

What is the current situation at the barrier lake?

The barrier lake is located approximately 10 kilometres upstream of the Gyirong border port. By Friday morning, its storage capacity had grown to over 2.5 million cubic metres. Chen Hanxiao, a member of the monitoring team dispatched by China Anneng Engineering Rescue Lhasa Base, told CCTV that the barrier stretching across the river is about 150 metres long and 40 to 50 metres high.

Chen warned that the rocks and soil in the area are loose, and secondary collapses have already occurred several times above the barrier during assessment operations. Safety personnel are monitoring the area closely and have been instructed to withdraw immediately if they detect signs of significant displacement.

How are rescue teams responding to the new threat?

Helicopter rescue operations in Nepal's flood-hit Rasuwa district were stopped on Friday, and locals were seen rushing up a hill after reports that the lake had begun to overflow, according to the Reuters news agency. In China, rescue teams are waiting at a village several kilometres from the Gyirong border port while authorities analyse the risks and adapt their plans.

A top government official in Nepal's Rasuwa district confirmed that Chinese authorities had shared information about the lake overflowing, indicating continued cross-border cooperation despite the challenging conditions.

Could the barrier lake cause another major disaster?

Austin Lord, a senior fellow in the energy, water and sustainability programme at the Stimson Center think tank, said experts are monitoring two barrier lakes in the region. The second lake formed just below the fracture in a glacier that broke on Wednesday, causing the initial disaster. Chinese authorities are referring to this as an 'impact crater' and are assessing how a breach there would affect the lower lake.

Lord said breaches of either lake could trigger a small flood in the same flow path as the initial event, rather than a major disaster on the scale of Wednesday's devastation. However, he expressed concern for search and rescue personnel operating in the river corridor itself. The main challenge in the coming days will be if weather systems continue to increase the volume of water behind the lakes, putting more pressure on the dams and creating further risk of breach.

What are the main risks for rescue workers?

The primary concern is that ongoing rain could add significant amounts of water to the barrier lakes, increasing pressure on the natural dams. A breach could result in either a slow or sudden release of water, potentially triggering new flash floods or landslides in areas already identified as priorities for search and rescue operations.

Rescue teams have already contended with roads leading to the Gyirong border port being blocked for kilometres by thick mud and debris. The new threat from the overflowing lake adds another layer of complexity to an already challenging operation, as authorities balance the urgency of rescue efforts against the safety of their personnel.

'There is a very real possibility that it could trigger new flash floods or landslides, so it is extremely dangerous to proceed to the areas that have been identified as priorities for search and rescue operations,' CCTV reported.