A glacial lake outburst flood in Bhutan has damaged a solar-powered irrigation project and blocked a section of a highway with debris, and 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, and 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, and the flash flood also swept debris onto a section of the Punakha-Gasa Highway in the Dzomlingthang area.
The outburst was reported on Thursday evening at Shintaphu Lake, also known as Shintaphu Tsho, located below Wakila Mountain in Bhutan's Gasa district, in the upper reaches of the Mo Chhu river basin, and 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, and an official from the National Centre for Hydrology and Meteorology said a water-level monitoring station was located at Taktsimakhang, although no alert had been triggered there at the time of the initial reports, with the full extent of the outburst and its downstream impact still unclear.
What is a glacial lake outburst flood
A glacial lake outburst flood occurs when water stored in a lake formed by melting glaciers is suddenly released, which can happen when a natural barrier holding the water fails or is breached.
The resulting surge can travel rapidly through mountain valleys, carrying large amounts of debris and damaging settlements, roads, bridges and farmland.
Shintaphu Lake lies within Bhutan's Punatsangchhu river basin, and the river is known as the Sankosh after it enters India, which makes a sudden release of water a concern for downstream communities.
India issues flood alerts in Bengal and 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, and 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, including the Darjeeling hills, Jalpaiguri and Cooch Behar districts, and NDRF and SDRF teams have been deployed in Tufanganj and Boxirhat in Cooch Behar district, both along the Sankosh river near the Assam border, with residents being alerted about the possible threat.
According to the advisory, floodwater was expected to reach the India-Bhutan border within six to eight hours, and 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, warning in a video message that a surge of water could reach the river in Kumargram within the next one to one-and-a-half hours, and appealing 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, urging people in the catchment areas to move to safer locations immediately and stay alert.
The Sankosh flows from Bhutan into India and supports communities across parts of northern West Bengal and adjoining Assam, and a sudden rise in its water level could threaten riverside settlements, livestock, farmland and infrastructure, while authorities are monitoring the situation and assessing the movement of floodwater and the possible impact on downstream communities.
All residents safe in Indian areas, over 4,000 shifted to shelters
The flash flood transition period has passed, and all residents in the Indian areas, including districts in West Bengal and Assam, are safe, with people living in vulnerable areas moved to relief shelters as a precaution.
Alipurduar Superintendent of Police Amit Kumar Shaw said the situation was under control and urged residents not to panic, saying the police, district administration and other agencies were working in close coordination, with SDRF personnel deployed, an NDRF team on its way, and a Civil Defence team assisting with preparations.
Shaw said approximately 4,000 to 5,000 people had been moved into shelters, utilising school buildings as relief centres, and additionally more than 6,000 people had been relocated to safe areas.
The SP said the intensity of the water flow had decreased slightly, based on the latest information received from Bhutan, although the administration remained on high alert, and the police, the district magistrate's office and the block development officer's office had arranged dry food and drinking water along with other necessities such as toilet facilities.
Shaw added that a red alert remained in effect for the Sankosh river system, and warned that the water flowing through the river could carry dead fish and large pieces of wood and concrete debris.
According to details shared by the Kumargram block administration, residents were moved to 18 flood shelters across the block, including schools, community halls, religious institutions and tea garden facilities, and people from Assam also took shelter in safe places.
