Glacial lakes in Nepal and Tibet’s Himalayan regions could pose a flood risk to northern India if their natural dams fail, sending water, ice and debris into downstream river systems. Bihar could face the greatest impact among the Indian states mentioned because Nepal’s Koshi and Gandaki rivers flow into the state.
The assessment identifies 47 potentially dangerous lakes in the Hindu Kush Himalaya. Of these, 25 are in Nepal, 21 in Tibet and 1 in India. The lakes are distributed across 42 sites in the Koshi basin, 3 in the Gandaki basin and 2 in the Karnali basin. Together, the Koshi and Gandaki basins contain about 96 percent of the identified lakes.
Why Bihar faces the greatest exposure
The Koshi and Gandaki rivers cross from Nepal into Bihar. A major glacial-lake event in either basin could therefore carry its effects from the Himalayan region into the plains. There are 45 potentially dangerous lakes in the 2 basins combined.
The possible mechanism is a glacial lake outburst flood, or GLOF. If a natural barrier gives way, a sudden surge containing water, ice and debris can move downstream. The reported risk extends beyond Bihar to parts of Uttar Pradesh and Uttarakhand through river systems connected to Nepal and Tibet.
River links to Uttar Pradesh and Uttarakhand
The Karnali River of Nepal continues downstream as the Ghaghra, also known as the Saryu, in India. Its upper catchment extends into Tibet. An event in the upper glacial areas of Tibet could therefore affect the Karnali-Ghaghra system, creating concern for Uttar Pradesh.
In Uttarakhand, Nepal’s Mahakali River flows as the Kali River. A glacial lake in Nepal’s Mugu area and another lake in the Kali River basin have been classified as dangerous. Their failure could threaten Pithoragarh and nearby areas.
219 hanging glaciers in the Alaknanda basin
Uttarakhand’s Alaknanda basin has 219 identified hanging glaciers. They cover 71.7 square kilometres and hold an estimated 2.39 cubic kilometres of ice. Their average slope is about 33.6 degrees.
A break in the ice could trigger an avalanche, block a river or produce a sudden flood. Some similar lakes have also been identified in the Alaknanda and Bhagirathi valleys.
Glacier change across the Hindu Kush Himalaya
An assessment by the International Centre for Integrated Mountain Development, or ICIMOD, issued in March 2026 counted more than 63,700 glaciers across the Hindu Kush Himalaya. They cover about 55,782 square kilometres. The assessment also reported that the rate of ice melt has doubled since 2000.
A senior geologist said the Himalayan region contains many such lakes and hanging glaciers and that monitoring is needed. The same assessment described the reported events in Nepal and Tibet as natural phenomena.
