Bhutan GLOF triggers downstream alerts, underscores need for stronger early warnings systems across the Himalaya 

Kathmandu, 30 October 2026 – The glacial lake outburst flood (GLOF) from Sintaphu Lake in Bhutan has triggered downstream alerts in the Indian states of West Bengal and Assam, drawing attention to the growing risks posed by high-mountain hazards across the Hindu Kush Himalaya (HKH).

Communities and media are advised to follow the official warnings and advisories issued by Bhutan’s National Centre for Hydrology and Meteorology (NCHM) and the relevant disaster management authorities in India.

“The timely warnings issued by Bhutan’s authorities demonstrate the value 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 critical to protecting vulnerable communities across the Himalaya.”

Before the outburst, Sintaphu Lake was estimated to contain 6 to 7 million cubic metres of water, equivalent to appropriately 2,400–2,800 Olympic-sized swimming pools. The volume of water released  remain under assessment.

The event comes as countries across the region face a series of mountain hazards. It follows the destructive rock-ice avalanche in Nepal’s Gyirong-Rasuwa river channels in August and the Budhi Gandaki flash flood in late October. Together, these events highlights the importance of timely warnings, preparedness and transboundary coordination.

ICIMOD research shows that effective disaster risk management depends on understanding not only the hazard itself, but also who and what is exposed downstream and how vulnerable they are. Early warning systems are most effective when they are people-centred, reach communities in time, and provide clear guidance on what actions to take.

Regional context:
While Bhutan’s NCHM monitors dozens of potentially dangerous glacial lakes domestically within the country, the Sintaphu outburst reflects a wider regional challenge.

Previous assessments by ICIMODand UNDP identified 47 major potentially dangerous glacial lakes (PDGLs) across the transboundary Koshi, Gandaki and the Karnali river basins. Current estimates show that 388 GLOFs have been documented across the HKH, including the Karakoram, Central and Eastern Himalaya.

History of GLOF activity in Bhutan:
In 2015, a GLOF in the headwaters of the Mo Chuu River, where Sintaphu Lake is located, prompted Bhutanese authorities to work with the SERVIR-Himalaya initiative to assess glacial lakes risks in the catchment.

Bhutan’s National Centre for Hydrology and Meteorology continues to monitor potentially dangerous glacial lakes many of which are held back by unstable moraine that can degrade over time.

Ongoing risk reduction efforts
ICIMOD works with regional partners to strengthen hazard monitoring, forecasting, and early warning systems across the HKH.

Current initiatives include:

The Sintaphu event demonstrates the importance of end-to-end early warning systems that combine monitoring, timely alerts, clear communication, and preparedness before disaster strikes.