Bhutan glacial lake bursts in Gasa, wrecking hot springs and a highway as over 10,000 are moved in India's Alipurduar
Sintaphu Lake burst on October 29, damaging Gasa's hot springs and a highway. No deaths are reported, but India moved over 10,000 from the Sankosh's path.
At a glance
- Sintaphu Lake in Bhutan's Gasa district burst on the evening of October 29; no deaths or injuries had been reported by Friday morning.
- The flood hit the Gasa Tshachu hot springs and washed away part of the Punakha-Gasa highway near the 31.85 km point, which is closed until further notice.
- Police in India's Alipurduar district said more than 10,000 people were moved, with 4,000-5,000 of them in temporary shelters.
- Assam's disaster authority said its river levels had not risen and no evacuation had begun in Dhubri or other Lower Assam districts.
- The cause and the volume of water released are still unconfirmed.
A glacial lake burst high in northern Bhutan on the evening of Thursday, October 29, sending a flood down the Mo Chhu river that struck the country's best-known hot springs and tore away part of a highway. No deaths or injuries had been reported by Friday morning. Across the border in India, police in West Bengal's Alipurduar district said more than 10,000 people had been moved away from the Sankosh river as a precaution.
The lake is Sintaphu, also spelled Shintaphu, below Wakila Mountain in the Laya area of Gasa district. Its water feeds the river system that becomes the Sankosh when it enters India. What set off the burst, and how much water escaped, had not been established in the latest reports.
The flood's path from Laya to the Indian plains
Floodwater reached Taktsemakhang at about 8:15 pm on Thursday, damaging the road to Laya, a remote highland community. Warning sirens sounded and people in exposed places were evacuated before the surge arrived.
The route below explains why two Indian states reacted to a flood in a thinly populated Himalayan valley.
| Stretch | River | What was reported |
|---|---|---|
| Sintaphu Lake, Laya, Gasa | Headwaters | Outburst on the evening of October 29 |
| Taktsemakhang | Mo Chhu | Water arrived about 8:15 pm; road to Laya damaged and closed |
| Gasa Tshachu | Mo Chhu | Hot spring complex badly hit |
| Punakha-Gasa highway, near 31.85 km | Mo Chhu | Section washed away; closed to all traffic |
| Dochhukha-Dzomlingthang-Ritsa, Punakha | Mo Chhu | Solar irrigation system partly damaged |
| Punakha | Mo Chhu joins Pho Chhu | Forms the Punatsangchhu |
| Alipurduar, West Bengal; Dhubri, Assam | Sankosh | Alerts; precautionary moves in Alipurduar |
How badly Gasa Tshachu and the highway were hit
Accounts of the damage differ, and officials said a full assessment was still under way. Reports from Bhutan said the Gasa Tshachu complex beside the Mo Chhu was washed away, while others described it as damaged. Darkness and the force of the water prevented an immediate check on Thursday night, and two Bailey bridges may also have been lost.
The hot springs draw pilgrims and visitors from across Bhutan, and this is not the first blow. A flash flood in August 2021 pushed the Mo Chhu towards the same site and damaged it.
On the highway there is less doubt. Travellers have been told to put off non-essential journeys because the road is shut until further notice, which leaves Gasa and Laya harder to reach while crews work out what is left. Concern has also been raised in Bhutan about a large artificial lake that may have formed after river channels merged. That has not been confirmed.
Why more than 10,000 people moved in Alipurduar
India's Central Water Commission issued a special advisory dated October 29, saying a flash flood in the upper Punatsangchhu could cause a sudden rise in water levels in Alipurduar and Dhubri. The Indian embassy in Bhutan had passed on the first report of the outburst.
Alipurduar's police superintendent, Amit Kumar Shaw, said 4,000 to 5,000 people were in temporary shelters, including school buildings, and more than 6,000 others had gone to safer areas. Those are the only detailed figures available so far, and they come from the district administration.
"There is absolutely no need to panic," Shaw said, adding that the situation was under control. The administration arranged drinking water, dry food and sanitation for those displaced. Officials said the intensity of the flow had eased slightly, but the warning stayed in force.
Further east the picture was calmer. Assam's State Disaster Management Authority said no evacuation had started in Dhubri or other Lower Assam districts and that river levels there had not risen. Chief Minister Himanta Biswa Sarma said teams were on standby and watching vulnerable parts of Dhubri and Kokrajhar.
If you live along the Sankosh or plan to travel in Gasa
- Stay away from riverbanks. Communities along the Sankosh and its tributaries have been told to move from vulnerable banks, and police warned that floodwater could carry timber and concrete debris.
- Do not go home early. People moved in Alipurduar are being told to follow official instructions and wait for clearance.
- Check before driving. The Punakha-Gasa highway is closed to all traffic. Trips to Gasa and Laya should wait unless they are essential.
- Watch official channels. Warnings also cover Jalpaiguri, Cooch Behar and the Darjeeling hills.
A danger Bhutan already had on its list
Sintaphu is one of 17 lakes on Bhutan's official list of potentially dangerous glacial lakes. Being listed means a lake needs monitoring, not that it is expected to burst. Bhutanese specialists studied Sintaphu in May and June 2023, and monitoring equipment was installed.
Bhutan knows the cost when such a warning comes too late. In October 1994, an outburst from Luggye Tsho killed 21 people downstream in Punakha. In October 2023, South Lhonak Lake in India's Sikkim burst, destroyed a major dam on the Teesta and left dozens dead, with many more missing. No deaths have been reported from this flood so far, though damage in Gasa is still being counted.
The threat stretches across the Himalaya and Karakoram. Pakistan counts more than 3,000 glacial lakes in Gilgit-Baltistan and Khyber Pakhtunkhwa, and an outburst from Shishper glacier destroyed the Hassanabad bridge on the Karakoram Highway in May 2022. Warming temperatures are growing many of these lakes, and rock and ice dams can fail with little notice.
What officials still have to answer
Three questions remain open: what caused the burst, how much water came out, and whether Sintaphu or any new lake downstream still poses a risk. Authorities in Bhutan are assessing the lake and the damage, while North Bengal officials continue to watch the Sankosh and coordinate with their Bhutanese counterparts. The Punakha-Gasa highway stays closed until engineers can reopen it.
Questions people are asking
What is a glacial lake outburst flood?
It is a sudden release of water from a lake held behind ice or loose rock left by a glacier. The surge can travel far down a valley within hours, carrying boulders, timber and debris.
Which areas of India are on alert after the Bhutan lake burst?
Alipurduar district in West Bengal and Dhubri in Assam were named in the Central Water Commission's advisory. Warnings also reached Jalpaiguri, Cooch Behar and the Darjeeling hills, and Assam is watching Kokrajhar.
