Bhutan GLOF Forms New Downstream Lake, Raises Secondary Flood Concerns

Summary

A glacial lake outburst flood (GLOF) that began in Bhutan on Oct 29 created a temporary lake at Taktsemakhang in the Sintaphu‑Lungu river confluence. Authorities in India and Bhutan are monitoring the new water body for possible secondary flooding.

Details

• Origin: The GLOF originated from the Shintaphu glacial lake in Bhutan, which ICIMOD estimates held 6‑7 million m³ of water (about 2,400‑2,800 Olympic‑size pools). The exact volume released is still being assessed.
• New lake: Bhutan’s National Centre for Hydrology and Meteorology (NCHM) confirmed the formation of an artificial lake at Taktsemakhang, where the Sintaphu Chhu meets the Lungu Chhu (Gangchen Tag Chhu). Monitoring stations recorded a rapid rise in water level, peaking at 6.7 m at Yebesa on 28 Oct, then falling to 2.84 m within 90 minutes.
• Indian response: The Central Water Commission (CWC) issued a special flood advisory for West Bengal and Assam. In West Bengal, the Sankosh River rose 1.5 m but receded quickly; no damage was reported. Flood shelters were opened in Alipurduar district, housing around 10,000 people from the Sankosh banks and a few thousand from Assam.
• Official statements:
• Assam Chief Minister Himanta Biswa Sarma said teams are on standby and residents should stay alert.
• NCHM warned people in the Mochhu and Punatsangchhu valleys to avoid riverbanks and low‑lying areas.
• Impact in Bhutan: According to the national daily *Kuensel*, floodwaters damaged roads, bridges and the Punakha‑Gasa secondary highway, but no casualties were reported.
• Expert view: Glacial‑hazard specialist Ashim Sattar (IIT Bhubaneswar) explained that temporary downstream lakes are a known risk after GLOFs. They can drain naturally but may become secondary flood hazards if not continuously monitored.

Practical implications

• Residents in the affected valleys should follow updates from NCHM and local disaster management agencies.
• The early‑warning sirens activated on 28 Oct likely prevented loss of life; continued vigilance is essential until the lake either drains or is safely managed.
• Verification of the situation can be done through NCHM bulletins, CWC advisories, and on‑ground reports from district administrations in Alipurduar (West Bengal) and Kokrajhar/Dhubri (Assam).

Context

• The Himalayas host 47 major potentially dangerous glacial lakes (PDGLs) across trans‑boundary basins, and 388 GLOFs have been recorded in the region.
• Past events, such as the 2015 GLOF in the Mo Chuu river headwaters, prompted joint risk‑assessment initiatives between Bhutan and the SERVIR‑Himalaya program.

--- *All information is drawn from the Times of India report dated 30 Oct 2024 and statements from NCHM, CWC, Assam government and expert commentary.*