"Recent glacial lake outburst destroyed bridges, disrupted travel, and highlights urgent need for early warning systems in Nepal’s mountain regions"

KATHMANDU: A sudden glacial lake outburst flood (GLOF) in Upper Mustang has renewed concerns over the increasing threat posed by high-altitude glacial lakes in Nepal. 

The flood, which occurred on July 8, was caused by the rapid drainage of a seasonal ice-dammed lake at 5,900 meters near an unnamed glacier feeding the Chhuhama River, a tributary of the Kali Gandaki.

According to a Rapid Hazard and Risk Assessment published by HiRISK, the lake had grown to 0.016 square kilometers before draining subglacially over 500 meters. The resulting flood damaged four bridges and left sediment deposits stretching 35 kilometers downstream. Damages have been estimated at Rs 15 million.

Residents in Chumjung and Lo Manthang spotted the flood early and warned others, allowing for timely evacuation and preventing serious casualties.

Experts warn the region remains vulnerable to further events due to loose sediments and the presence of several similar ice-marginal lakes. These lakes form during warmer months and are difficult to detect using common satellite tools, making real-time monitoring more important than ever.

This GLOF ranks as the third highest documented in High Mountain Asia and comes just hours after a similar flood struck Rasuwagadhi in Rasuwa district, sweeping away the Miteri Bridge and leaving at least 20 people missing.

The back-to-back floods have prompted urgent calls from scientists and agencies such as ICIMOD for better early warning systems and climate resilience planning. Currently, only a few glacial lakes in Nepal, like Imja and Tsho Rolpa, are equipped with early warning infrastructure.

With glacial lakes forming even at elevations above 6,000 meters, and rising temperatures accelerating glacier melt, experts say Nepal must invest in high-resolution monitoring and preparedness to protect mountain communities and tourism routes in the Himalayas.