ISRO’S STUDY ON GLACIAL LAKE (Syllabus GS Paper 3 – Env & Eco)

Context: The Indian Space Research Organisation (ISRO) recently published satellite-data-based analysis on the expansion of glacial lakes in the catchments of Indian Himalayan river basins.

ISRO's Glacial Analysis

• Long-term Satellite Imagery: It covering Indian Himalayan river basins, including India, Nepal, Tibet, and Bhutan, is available from 1984 to 2023.
• Expansion of Glacial Lakes: Out of 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes had expanded significantly since 1984.
• Magnitude of Expansion: Among the expanded lakes, 601 lakes had more than doubled in size, 10 lakes had grown between 1.5 to 2 times, and 65 lakes had grown 1.5 times.
• Distribution in India: ISRO identified that 130 out of the 676 expanded lakes are situated in India, particularly in the Indus (65), Ganga (7), and Brahmaputra (58) river basins.
• Impact of Global Warming: The expansion of these lakes is attributed to the accelerated retreat of glaciers, which is linked to global warming.
• Category: ISRO categorised glacial lakes into four broad categories based on how they were formed: Moraine-dammed, Ice-dammed, Erosion-based, and ‘others’.

Glacial Lakes

• About: It is defined as a body of water that is present in adequate quantities, extends with a free surface in, beneath, beside, and/or in front of a glacier, and is the result of glacier activities and/or glacier retreating processes.

Glacial lake outburst floods (GLOFs)

• About: They occur when glacial lakes release large volumes of meltwater due to the failure of natural dams… resulting in sudden and severe flooding downstream.
• Method of mitigation:

o According to a study published in Journal of Geophysical Research which examined the risks posed by Ghepan Gath lake (Himachal Pradesh) è lowers the lake/water levels by 10 to 30 m significantly reduces the impacts.

o One way to syphon off lake water is by using long High Density Polyethylene (HDPE) pipes. In 2016, members of the Sikkim State Disaster Management Authority and Sikkim’s Department of Science and Technology and Climate Change, among others, used this method to reduce water levels in Sikkim’s South Lhonak Lake.