South Lhonak Lake

South Lhonak Lake in North Sikkim, India is a high-altitude glacial-moraine dammed lake situated around 5,200 meters above sea level. It was formed from the meltwater of the Lhonak Glacier, originating in the remote Lhonak Valley near the eastern edge of the Tibetan Plateau. In recent decades, the lake has expanded rapidly due to accelerated melting of surrounding glaciers, driven largely by global warming.

This growth has made South Lhonak Lake one of the most vulnerable in the region to glacial lake outburst floods (GLOFs), posing a significant environmental hazard to downstream communities and ecosystems. In October 2023, a major GLOF from the lake caused catastrophic flooding downstream, resulting in the destruction of critical infrastructure, including bridges and connectivity routes, loss of property, livestock, and lives, and severe impact on local agro-pastoral practices.

The government has responded by monitoring the lake, installing early warning systems, and implementing engineering solutions to drain excess water and reinforce natural barriers, aiming to reduce the risk of future disasters and protect local populations.