NEW DELHI: The glacial lake outburst flood (GLOF) from Sintaphu Lake in Bhutan has triggered downstream alerts in the Indian states of West Bengal and Assam, highlighting the increasing risks posed by high-mountain hazards across the Hindu Kush Himalaya (HKH).
GLOF is a sudden flood that happens when a lake formed by melting glaciers suddenly bursts or overflows.
The incident occurred on the evening of October 29 at Sintaphu Lake, located near Wakila Mountain in Lungo, Laya Gewog, in the Gasa district. The floodwaters rushed downstream to Taktsemakhang around 8 PM, damaging roads and bridges leading to Laya, one of Bhutan's most remote highland communities, effectively cutting it off from the mainland.
The Indian Embassy in Bhutan alerted Indian authorities about the GLOF incidents. The Central Water Commission issued a special advisory on October 29 to the relevant authorities in West Bengal and Assam.
More than 10,000 people have been relocated to safer areas in West Bengal’s Alipurduar district, while vulnerable regions in Assam’s Dhubri and Kokrajhar districts are being closely monitored.
The floodwaters from Sintaphu Lake have washed away the Gasa Tshachu hot spring complex and damaged the Punakha-Gasa highway. Authorities are still assessing the full extent of the damage, as Assam and West Bengal remain on alert for a potential rise in the Sankosh River.
As of Friday afternoon, there are no official reports of deaths or injuries related to the GLOF.
The Kathmandu-based inter-governmental organization ICIMOD, which focuses on the conservation of the Hindu Kush Himalaya region, indicated that this event is part of a broader pattern of mountain hazards affecting countries across the region.
ICIMOD reported that Sintaphu Lake contained between 6 to 7 million cubic meters of water, equivalent to approximately 2,400–2,800 Olympic-sized swimming pools. The volume of water released in the outburst is still being assessed.
The Sintaphu Lake GLOF follows a destructive rock-ice avalanche in Nepal’s Gyirong-Rasuwa river channels in August and a flash flood in the Budhi Gandaki region in late October. Together, these incidents highlight the importance of timely warnings, preparedness, and transboundary coordination.
Communities and media are encouraged to follow the official warnings and advisories from Bhutan’s National Centre for Hydrology and Meteorology (NCHM) and relevant disaster management authorities in India. While Bhutan’s NCHM monitors numerous potentially dangerous glacial lakes, the Sintaphu outburst reflects a wider regional challenge.
Previous assessments by ICIMOD and UNDP identified 47 major potentially dangerous glacial lakes (PDGLs) across the transboundary Koshi, Gandaki, and Karnali river basins. Current estimates indicate that 388 GLOFs have been documented across the HKH, including the Karakoram, Central, and Eastern Himalayas.
"The timely warnings issued by Bhutan's authorities illustrate the importance of sustained monitoring and effective early warning systems in reducing disaster risk,” said Pema Gyamtsho, Director General of ICIMOD. “As mountain hazards become more complex, continued investment in forecasting, preparedness, and cross-border cooperation will be essential to protecting vulnerable communities throughout the Himalaya."
Bhutan’s National Centre for Hydrology and Meteorology continues to monitor potentially dangerous glacial lakes, many of which are held back by unstable moraines that can degrade over time.
