Glacial lake bursts in Bhutan and triggers flood alerts in Bengal and Assam

A glacial lake burst in Bhutan on Thursday, sending floodwater toward the Indian border and triggering flash flood alerts across two states. Authorities in West Bengal placed Cooch Behar, Tufanganj and Busirhat districts along the Sankosh river and its tributaries on high alert and evacuated vulnerable areas, while settlements along the Brahmaputra in Assam were told to stay alert. India's Union water resources department said the floodwater would take six to eight hours to reach the Bhutan-India border and was likely to impact districts in both states.

The outburst occurred at Sintaphu lake, near Wakila mountain — and a new artificial lake is now forming at the site. Bhutan's Prime Minister Tshering Tobgay has inspected it; Tenzing Lamsang posted that "the large artificial lake is building up as we speak." Glacial lake outburst floods occur when a lake fed by glacial melt breaches suddenly, and they are becoming routine across the Himalayas as warming temperatures drive rapid snowmelt. Sikkim alone holds almost 700 glacial lakes, 21 of them identified as potentially dangerous with a high outburst probability. In Himachal Pradesh, the number of glacial lakes has grown by more than 500 percent since 1990.

Downstream, the official messages diverged. Alipurduar's police chief Amit Kumar Shaw told residents there was "absolutely no need to panic," while West Bengal's water resources minister Nisith Pramanik said people living near tea gardens in the state's north and on riverbeds "must evacuate immediately." Assam Chief Minister Himanta Biswa Sarma said the state was monitoring Dhubri and Kokrajhar districts and coordinating with the National Disaster Response Force.

In August, a glacial lake outburst on Nepal's border with China triggered a flash flood that killed nearly 1,500 people, injured more than 9,200 and left 5,000 missing.