A glacial lake in northern Bhutan burst on Thursday evening, sending a surge of water down the Mo Chhu river system and putting the Sankosh River on red alert in northern West Bengal and Assam, where authorities moved more than 10,000 people to safety.
The outburst occurred at Shintaphu Lake in Lungo, in Laya Gewog in Bhutan’s Gasa district, one of 17 glacial lakes Bhutan lists as potentially dangerous. Around 7.4 million cubic metres of water is estimated to have been released. The water flows from the Mo Chhu into the Punatsangchhu and enters India as the Sankosh.
Key Takeaways
- A glacial lake outburst at Shintaphu Lake in Bhutan’s Gasa district on October 29 released an estimated 7.4 million cubic metres of water into the Mo Chhu river system.
- More than 10,000 people were moved to safety in northern West Bengal and Assam as the Sankosh River was placed on red alert, with thousands more relocated to shelters.
- No casualties have been reported in Bhutan so far, but the flood washed away infrastructure at the Gasa Tshachu hot springs and damaged the road to Laya village.
Around 7.4 million cubic metres of water is estimated to have been released.
How the Flood Unfolded in Bhutan
Floodwater reached Taktsemakhang at about 8.15 pm on Thursday, damaging the road to Laya, washing away the Gasa Tshachu hot spring complex and cutting a section of the Punakha-Gasa highway, according to reports from Bhutan. State broadcaster BBS reported that no injuries or loss of life had been reported in Bhutan, and that two Bailey bridges may have been washed away.
Bhutan’s National Centre for Hydrology and Meteorology is monitoring river levels at Tashithang and Yebesa, and warning sirens were sounded. Bhutan’s national newspaper Kuensel reported that part of the road to Laya village had been washed away, making it impassable, and that the road had been closed to traffic indefinitely. The area had been evacuated before the flood reached it, Kuensel reported.
The Shintaphu glacial lake, located below Wakila Mountain, was considered one of Bhutan’s potentially dangerous glacial lakes. Glacial lake outburst floods happen when water held back by a glacier or a moraine dam is suddenly released, and in steep Himalayan valleys that water can travel fast and carry debris with it. That geography is part of why downstream warnings matter so much in this region, where rivers cross from high mountain valleys into densely settled plains within hours.
Evacuations Along the Sankosh in Bengal and Assam
A special advisory issued by India’s Union Ministry of Jal Shakti on Thursday for Assam and West Bengal said the Indian Embassy had reported a glacial lake outburst flood in Shintaphu Lake in Bhutan’s Punatsangchhu river basin. The advisory said the flood would reach the border in six to eight hours and impact Alipurduar district in West Bengal and Dhubri in Assam.
Authorities began evacuation measures late on Thursday night in villages along the Sankosh. Loudspeaker announcements were made in riverbank settlements under the Rampur-I gram panchayat area, asking residents to leave their homes and move to designated shelters. Residents of riverbank villages in Alipurduar district were seen leaving their homes with their cattle after the administration issued evacuation instructions.
Alipurduar is on red alert, with 4,000 to 5,000 people in relief camps and over 6,000 shifted elsewhere, according to officials. State Disaster Response Force and Civil Defence teams are deployed and a National Disaster Response Force team was moving in. Alipurduar Superintendent of Police Amit Kumar Shaw said school buildings were being used as relief centres and that the situation was currently under control.
West Bengal Water Resources Investigation and Development Minister Nisith Pramanik said a glacial outburst had occurred at Lemthang in Bhutan, with water from the lake flowing through the Mo river towards the Sankosh. He urged residents living near riverbeds in Tufanganj and adjoining areas in Cooch Behar to evacuate immediately in view of the potential flooding, and said everyone living in the catchment areas of the Sankosh river and all its connected tributaries had been asked to move to a safe distance immediately.
Warnings, River Levels and the Assam Response
West Bengal Forest and Environment Minister Manoj Kumar Oraon urged residents along the Sankosh to warn others without delay, with special alerts directed at forest villages and hamlets bordering the river, including the upper Sankosh forest village, the NKC Sankosh Tea Garden, Kumargram block, Chengmari, Valka Barabisa, Jharaguri and Pakriguri. He warned that floodwaters were expected to surge downstream and that people in low-lying areas should move to safer ground.
In Assam, the State Disaster Management Authority said the water level of the Sankosh river was steady as of 6.30 am on Friday. Officials also noted that the intensity of the floodwaters had decreased slightly, but the high alert remained in effect for the Sankosh river system, with continuous coordination between Indian and Bhutanese authorities.
The India Meteorological Department also forecast heavy rainfall in Alipurduar on Friday, which could further complicate the situation for rescue and relief teams. That combination of a glacial surge upstream and heavy rain downstream is exactly what disaster teams watch for, because rising local rainfall can keep river levels high even after the main surge has passed.
The response echoes other recent disaster relief operations in India, where early evacuations and shelter arrangements have limited casualties even when homes, roads and crops were damaged. In this case, the early warning from Bhutan, the advisory from New Delhi and the overnight evacuations along the Sankosh gave riverside communities time to move before the water arrived.
- Shintaphu Lake outburst in Bhutan’s Gasa district on October 29, 2026, releasing about 7.4 million cubic metres of water.
- Sankosh River on red alert in West Bengal and Assam, with more than 10,000 people moved to safety.
- Gasa Tshachu hot spring complex washed away and the road to Laya village damaged in Bhutan, with no casualties reported there so far.
- River levels in Assam reported steady on Friday morning, but the high alert remained in place.
Why Bhutan’s Glacial Lakes Are Closely Watched
Bhutan sits in the eastern Himalayas, where warming temperatures have expanded many glacial lakes over recent decades. A lake that grows behind a natural dam of ice and rock can become a hazard if that dam weakens or fails, and the steep valleys below leave little time between a breach and a surge reaching settlements. That is why Bhutan monitors a list of potentially dangerous lakes and why cross-border information sharing with India matters: the rivers that start in Bhutan’s mountains become the Sankosh and other rivers that flow through West Bengal and Assam.
Life in these mountain communities is closely tied to the rivers and the roads that follow them, and daily life across Bhutan’s Himalayan valleys depends on connections that a single washed-out road or bridge can break. When the road to Laya was cut and the hot spring complex was washed away, the immediate damage was to infrastructure and livelihoods, not only to the landscape. Rebuilding that access will matter as much to local residents as the flood warnings themselves.
What to Watch Next
Officials will keep watching river levels along the Mo Chhu, the Punatsangchhu and the Sankosh, and the high alert for the Sankosh river system remains in place even as the intensity of the floodwaters has decreased slightly. Authorities in West Bengal and Assam will continue to monitor whether heavy rainfall in Alipurduar pushes water levels up again, and whether the steady level reported in Assam on Friday morning holds.
The next updates to watch are the official assessments of damage in Bhutan, including the road to Laya and the Punakha-Gasa highway, the count of people still in relief camps in Alipurduar, and any change to the red alert for the Sankosh. Until those updates arrive, the picture remains one of a serious cross-border flood warning met by early evacuations, with no casualties reported in Bhutan so far and relief teams still deployed on both sides of the border.