Glacial Lake Outburst Flood (GLOF)

A glacial lake outburst flood (GLOF) is a release of meltwater from a moraine or ice dam glacial lake due to dam failure. GLOFs often result in catastrophic flooding downstream, with major geomorphic and socioeconomic impacts. The Thorthormi Tsho (Lake) of Bhutan runs the risk of experiencing a GLOF. In June 2019, sustained heat waves, a delayed monsoon and an unnatural rise in temperature melted huge volumes of ice and snow in Bhutan’s largest glacial lake , the Thorthormi Tsho (Lake), causing the water level to rise by almost two meters. This prompted Bhutan to issue a nationwide flood advisory. Scientists and seismologists cautioned that any major disturbance on the Thorthormi Tsho (Lake) could result in a Glacial Lake Outburst Flood (GLOF) that could hugely impact life, property and infrastructure. Satellite images showed much of the melting on Thorthomi took place between June 6 and 15 as temperatures escalated. On June 20 excess water drained into two smaller lakes located downstream causing one of them to burst due to its weak moraine entrapment. The incident led to a minor flood and it was observed that the excess water was due to the melting of ice in the glacier lake.Bhutan however is not the only country with this climate risk. In recent years, these glacial lakes been forming and expanding all over the Hindu Kush Himalayas due to climate change. As the temperature rises and glaciers melt faster, water starts accumulating and this collected water forms a lake that keeps expanding annually. Since these lakes are bound only by loose pebbles and moraine, the walls are prone to collapse under the weight of water from melted ice. India witnessed a GLOF of this kind in Uttarakhand in 2013 that created havoc.