Bhutan GLOF washes away Gasa hot spring complex, damages highway; assessment underway

Gasa: The reported glacial lake outburst flood (GLOF) at Sintaphu Lake in Bhutan has washed away the Gasa Tshachu hot spring complex and damaged a section of the Punakha-Gasa highway, according to Daily Bhutan, as authorities continue to assess the extent of the damage.

A Glacial Lake Outburst Flood (GLOF) occurs when water stored in a glacial lake is suddenly released, often due to a breach or weakening of its natural barriers, known as moraines. The resulting flood can rapidly travel through mountain valleys, carrying mud, rocks and debris and damaging roads, bridges and settlements.

In its latest update on Friday, Daily Bhutan reported that floodwaters following the reported lake outburst had washed away the well-known hot spring complex located beside the Mo Chhu River in Gasa district. The full extent of the damage is still being assessed.


A section of the Punakha-Gasa Secondary National Highway near the 31.85-kilometre point has also been completely washed away, prompting authorities to close the road to all traffic until further notice, the report said.

Travellers have been advised to postpone non-essential journeys or confirm alternative arrangements before departing.

The reported outburst occurred on Thursday evening, October 29, at Sintaphu Lake near Wakila Mountain in Lungo, Laya Gewog, in Bhutan's northern Gasa district.

According to Daily Bhutan, floodwater reached Taktsemakhang at around 8.15 pm on Thursday, damaging a section of the road connecting the remote highland community of Laya and forcing its closure. Laya is one of Bhutan's most remote highland communities.

Precautionary evacuations were carried out in potentially exposed locations, while warning sirens were activated. No deaths or injuries had been reported as of the morning of October 30.

The cause of the water release, the volume of water involved and the full extent of the damage remain unconfirmed, the report added. Authorities are continuing to assess lake conditions and downstream impacts.

The water from Sintaphu Lake enters the Mo Chhu, which flows south through Gasa and Punakha. At Punakha, the Mo Chhu meets the Pho Chhu to form the Punatsangchhu, which later enters India as the Sankosh River.

Sintaphu is a high-altitude glacial lake at the headwaters of the Mo Chhu and appears on Bhutan's official list of 17 potentially dangerous glacial lakes, Daily Bhutan reported.

The classification means the lake requires continued monitoring, not that an outburst is certain. Bhutanese specialists studied the lake between May and June 2023, and monitoring equipment has been installed in the area.

The study involved measuring the main and upper lakes, examining the surrounding terrain and moraine barriers, and monitoring the glacier that feeds the lake. Bhutan has also deployed monitoring equipment in the area to strengthen surveillance and mitigate potential glacial flood risks.

The reported outburst had prompted precautionary warnings in neighbouring India, particularly across North Bengal, where communities along the Sankosh River and its tributaries were advised to move to safer locations.

Meanwhile, the Central Water Commission (CWC) issued a special flood advisory for West Bengal and Assam, warning of a sudden rise in water levels in Alipurduar and Dhubri districts following the reported GLOF at Bhutan's Shintaphu Lake. Both states were placed on alert, with local authorities advised to closely monitor the Sankosh River and take precautionary measures.