Glacial lake outburst in Bhutan; 5 districts in Assam and Bengal on flood alert

A glacial lake outburst in Bhutan has triggered evacuation warnings for downstream areas in West Bengal, with special advisories issued for parts of West Bengal and Assam. Authorities are assessing the water discharge and closely monitoring the Sankosh River for a possible sudden rise in water levels.

In Short

• Bhutan sounds sirens, urges residents near riverbanks to move safer areas
• India issues special advisory for West Bengal and Assam over Sankosh River
• Outburst scale and downstream impact remained unclear during initial assessments

A glacial lake outburst flood (GLOF) in Bhutan has damaged a solar-powered irrigation project and blocked a section of a highway with debris. There have been no reports of casualties in the country so far.

The flash flood has also raised concerns in India, prompting authorities to issue flood alerts in parts of West Bengal and Assam over a possible surge in the Sankosh River.

The Solar Irrigation Lifting System in Dochhukha-Dzomlingthang-Ritsa Chiwog, under Guma Gewog in Punakha, was partially damaged by the flash flood. The system has stopped functioning, although the full extent of the damage is yet to be assessed.

According to a local leader, the irrigation system was installed earlier this year to address water supply problems faced by residents of the chiwog.

The flash flood also swept debris onto a section of the Punakha-Gasa Highway in the Dzomlingthang area. The information was shared by the Tshogpa of Dochhukha-Dzomlingthang-Ritsa Chiwog.

The outburst was reported on Thursday evening at Shintaphu Lake, also known as Shintaphu Tsho, located below Wakila Mountain in Lungo, Laya Gewog, in Bhutan's Gasa district. The lake lies in the upper reaches of the Mo Chhu river basin. When it overflows, the water drains southwards into the Mo Chhu, triggering a surge downstream.

Shintaphu Lake is among Bhutan's 17 potentially dangerous glacial lakes. An official from the National Centre for Hydrology and Meteorology (NCHM) said a water-level monitoring station was located at Taktsimakhang. However, no alert had been triggered there at the time of the initial reports. The full extent of the outburst and its downstream impact remain unclear.

WHAT IS A GLACIAL LAKE OUTBURST FLOOD?

A GLOF occurs when water stored in a lake formed by melting glaciers is suddenly released. This can happen when a natural barrier holding the water fails or is breached.

The resulting surge can travel rapidly through mountain valleys. It can carry large amounts of debris and damage settlements, roads, bridges and farmland.

Shintaphu Lake lies within Bhutan's Punatsangchhu river basin. The river is known as the Sankosh after it enters India. This makes a sudden release of water a concern for downstream communities.

INDIA ISSUES FLOOD ALERTS IN BENGAL, ASSAM

Following the outburst, the Government of India issued a special advisory warning of a possible sharp rise in water levels along the Sankosh River.

Authorities warned that a flash flood in the upper reaches of the Punatsangchhu River could cause a sudden rise in water levels in West Bengal's Alipurduar district and Assam's Dhubri district.

Alerts have also been issued across parts of North Bengal. These include the Darjeeling hills, Jalpaiguri and Cooch Behar districts.

NDRF and SDRF teams have been deployed in Tufanganj and Boxirhat in Cooch Behar district. Both locations are along the Sankosh River, near the Assam border. Residents are being alerted about the possible threat.

According to the advisory, floodwater was expected to reach the India-Bhutan border within six to eight hours. Authorities in the affected districts have been asked to monitor the situation closely and take precautionary measures.

WEST BENGAL MINISTER URGES RESIDENTS TO EVACUATE

West Bengal Forest Minister and Kumargram MLA Manoj Kumar Oraon urged people living along the Sankosh River in Alipurduar district to move to safer locations.

In a video message posted on Facebook, Oraon warned that a surge of water could reach the river in Kumargram within the next one to one-and-a-half hours. He appealed to residents to evacuate as a precaution and cooperate with the administration.

BJP MP from Darjeeling, Raju Bista, also issued a public safety alert for people living along the Sankosh River.

In a post on X, Bista said a GLOF had been reported at Lemthang in Bhutan. He said the overflowing water was moving downstream through the Mofu River towards the Sunkosh River.

He urged people living in the catchment areas of the Sunkosh and its connected tributaries to move to safer locations immediately.

"Everyone in our Darjeeling hills, Terai and Dooars region are requested to stay alert," he added.

The Sankosh flows from Bhutan into India and supports communities across parts of northern West Bengal and adjoining Assam. A sudden rise in its water level could threaten riverside settlements, livestock, farmland and infrastructure.

Authorities are monitoring the situation and assessing the movement of floodwater and the possible impact on downstream communities.

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