The factor behind Bhotekoshi flood: Glacier lake outburst

Summarry:
On July 8, 2025, a flood occurred in the Bhotekoshi River flowing through Rasuwa Gadhi, Nepal, caused by the bursting of a supraglacial lake (a lake formed on the surface of a glacier) on the Purepu glacier approximately 36 km north of the Nepal-China border near Rasuwa Gadhi.

Preliminary reports from Nepal's Department of Hydrology and Meteorology, based on Sentinel-2 satellite images from the Copernicus data ecosystem, along with studies by international scientists including Nepali experts at the University of Alaska Fairbanks and Chinese Academy of Sciences, confirmed the lake's expansion and sudden outburst.

Key findings:

• The supraglacial lake expanded rapidly from March 25 to early July 2025, merging into a large lake on July 7.
• On July 8, the day of the outburst, the lake’s area suddenly decreased as water was released, triggering the flood downstream.
• Climate change and rising temperatures over recent decades have contributed to the formation and expansion of such glacier lakes.
• The affected area has experienced similar glacier lake outbursts before, and there is a risk of recurrence within this year due to remaining water in the lake basin.
• Currently, no early warning system is established for this area.

The flood damaged more than 10 hydropower projects in Rasuwa and Nuwakot districts.

Further ground-based reports from China and additional satellite data will help confirm and update findings. Continuous monitoring and timely information dissemination are planned by Nepal's Department of Hydrology and Meteorology.

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