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Hindu Kush Himalayas are experiencing an alarming rise in glacial-origin floods, according to scientists from the International Centre for Integrated Mountain Development (ICIMOD). A glacial lake outburst flood (GLOF) occurs when water is suddenly released from a lake fed by a melting glacier.
In the 2000s, a glacial origin flood was expected to hit the Hindu Kush Himalaya region once every five to 10 years. However, in the last two months alone — during May and June 2025 — ICIMOD has recorded three such floods in the region: in Nepal (Limi), Afghanistan (Andorab valley) and Pakistan (Chitral, Hunza).
“The acceleration of these types of events is completely unprecedented in the Hindu Kush Himalayan region. We need to delve deeper into the triggers that are resulting in cascading impacts,” Saswata Sanyal, ICIMOD Disaster Risk Reduction Lead, said in a statement.
The Hindu Kush Himalaya region covers 3,500 kilometres across Asia, spanning eight countries — Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal and Pakistan. Up to two billion people are dependent on the region for food, water and energy security. It is also home to many irreplaceable species.
Glacial-floods are driven by temperature. Sustained warming plays a key role in the formation and gradual expansion of glacial lakes. Short-term temperature extremes on individual days, too, can trigger sudden events such as ice avalanches, ice calving, or slope failures related to thawing of permafrost. Permafrost is any type of ground — from soil to sediment to rock — that has been frozen continuously for a minimum of two years.
Further, ICIMOD has also highlighted a new trend: Recent GLOF events have occurred due to the draining of newly formed (supraglacial) ice-dammed glacial lakes. This includes this week’s flood in Bhotekoshi Nadi in Rasuwa in Nepal.
The supraglacial lakes form on the surface of glaciers, particularly in debris-covered areas. They begin as small meltwater ponds before gradually expanding and sometimes merging to form larger supraglacial lake, making them highly dynamic.
The lake that caused the recent Nepal hazard was small in December 2024, before growing significantly a few months later in June 2025. Previously, only those greater than 0.02 square kilometres were considered risky. Priority, according to ICIMID, was given to potential downstream impacts and moraine-dammed glacial lakes, since these are considered particularly unstable. Nepal has 25 potentially dangerous lakes, Tibet Autonomous Region of China has 21 and India has one.
Supraglacial lakes are difficult to detect. Freely available satellite data, such as from Landsat and Sentinel-2, have limited resolution and can typically only identify lakes above a certain size threshold, potentially missing smaller or short-lived water bodies. The spatial resolution of satellite imagery is important to detect such lakes.
The researchers called for an increase in mapping and monitoring efforts, updating potentially dangerous glacial lakes inventories, analysing smaller, short-lived ice dammed lakes and incorporating the processes involved in glacier retreat and lake formation for more dynamic and accurate hazard assessment. “We’re talking about a huge expanse of terrain where these sorts of lakes can develop, and the monitoring data and method to keep on top of pace of changes we’re now seeing simply does not yet exist,” Qianggong Zhang, head of Climate and Environmental Risks at ICIMOD, said in a statement.
The researchers also projected that by the end of 2100, there will be a three-fold increase in GLOF risk across Hindu Kush Himalayas.
