A catastrophic glacier collapse in the Himalayas has triggered a secondary crisis, with the formation of a precarious barrier lake on the Nepal-China border. Following the initial disaster on Wednesday, which resulted in 469 confirmed deaths and left over 1,000 people missing across Nepal and Tibet, a new river breach on Friday has further complicated the situation. The rising water levels have forced an immediate halt to ongoing search and rescue operations in the affected region.
Officials in Nepal’s Rasuwa district reported on Friday that the barrier lake has begun to overflow. Narendra Pariyar, the district’s most senior official, expressed concern over the lack of precise data regarding the lake’s dimensions and water volume, noting that the rising river levels are clearly visible. The lake is situated near the confluence of the Chhochen Khola and Purepu Tsangpo rivers, part of the Lhende river system, which flows into the Bhotekoshi and Trishuli rivers toward Kathmandu.
Scientific analysis indicates that the disaster has resulted in two distinct lakes. One has formed in the upper reaches near the glacier where meltwater is trapped, while a second, larger, and more hazardous lake has formed downstream in Nepal. This lower lake was created when a massive landslide deposited rock, ice, and debris into the valley, effectively damming the river. Experts from Nepal’s National Disaster Risk Reduction and Management Authority (NDRRMA) have warned that the rising water levels pose a significant risk of a sudden, destructive burst.
Chinese authorities have deployed an eight-member engineering team to conduct aerial surveys and 3D modeling of the site. Engineer Chen Hanxiao reported that the collapse has left the surrounding landscape unstable, characterized by numerous isolated and steep cliffs that hinder access. Pawan Bhattarai, an assistant professor at Tribhuvan University, noted that the ice-rock avalanche deposited a massive volume of material into the valley, creating a natural dam that was likely impossible to prevent.
Nitesh Khadka, a physical geographer specializing in glacial floods, confirmed that satellite imagery and drone footage show two separate lakes. He explained that while the upper lake formed due to blocked drainage of meltwater, the lower lake on the Lhende river is a direct result of the landslide. Khadka noted that while controlled breaching could theoretically mitigate danger, the complex and remote terrain makes such interventions highly infeasible.
The scale of the potential threat is significant. China’s Ministry of Water Resources estimated on Thursday that the barrier lake currently holds between 1.5 and 2 million cubic meters of water, with an additional 3 million cubic meters expected to flow in over the next three days. This total volume is roughly equivalent to 1,200 Olympic-sized swimming pools. Experts warn that a sudden breach in such a steep valley would generate a fast-moving, debris-laden flood with minimal warning for downstream populations.
The environmental impact of such a breach would be severe, as the floodwaters would likely mobilize massive amounts of sediment, further complicating search and rescue efforts. Beyond the immediate threat to survivors, the instability poses risks to infrastructure, including hydropower tunnels located downstream. While the natural process of lake formation cannot be entirely stopped, researchers emphasize that improved satellite monitoring, rapid detection of river blockages, and real-time river data could help reduce the risks to vulnerable communities in the future.
This event follows a history of similar glacial disasters in the region. In July 2016, a glacier detachment in Tibet’s Aru Range released 68 million cubic meters of ice, killing nine herders, followed by another collapse two months later. In November 2022, a 40-million-cubic-meter ice detachment from the Bukadaban Feng glacier in China’s Qinghai province created a 13-meter high wave after crashing into a lake. Additionally, a May 2022 flood in Pakistan’s Hunza Valley was caused by the sudden breach of an ice-dammed lake, underscoring the recurring nature of these climate-driven hazards. The report also notes that he added that it is currently unclear how high the water level is. The report also notes that however, there are challenges when it comes to accessing the site. The report also notes that the surrounding area is not in a position to hold it, when sudden lakes form. The report also notes that additionally, when a barrier lake is held behind only by loosely packed rocks and mud, even moderate overflow can erode the barrier and trigger a sudden, destructive outburst flood downstream. The report also notes that “It is a threat, because if a formed lake suddenly breaches it may cause another flood; it may mobilise the sediments that will hamper search and rescue operation and will also put dangers to those surviving in the hydro tunnels,” Khadka said.