The Indian Space Research Organization (ISRO) has issued a warning that over 27% of the identified glacial lakes in the Himalayas have significantly expanded since 1984, with 130 of those lakes located in India.

1. Long-term satellite imagery from 1984 to 2023 reveals significant changes in glacial lakes in the catchments of Indian Himalayan River basins.
2. Out of 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes have notably expanded since 1984.

What are glacial lakes?

1. Glacial lakes form when glaciers erode land and then melt, filling the depression created by the glacier.
2. These lakes play a crucial role as freshwater sources for rivers in the Himalayan region.
3. Glacial lakes can be categorized into 4 broad types based on their formation process:

1. moraine-dammed
2. Ice-dammed
3. erosion
4. other glacial lakes
4. Glacial lakes also pose significant risks, such as Glacial Lake Outburst Floods (GLOFs), which can have devastating consequences for downstream communities.

What is Glacial Lake Outburst Flood (GLOF)?

1. GLOFs are flash floods caused by the outburst of glacial lakes, often formed by landslides in the Himalayan region.
2. The sudden release of large amounts of water has the potential to cause catastrophic flooding downstream in a GLOF.

1. When natural dams, such as moraines or ice dams, fail, glacial lakes release large amounts of meltwater, resulting in sudden and severe flooding.
2. Dam failure can be caused by a variety of factors, including snow or rock avalanches, extreme weather events, and other environmental factors.

Key findings by the ISRO:

1. Monitoring and studying glacial lakes in the Himalayan region is challenging due to the rugged terrain.
2. Satellite remote sensing technology is an effective tool for inventory and monitoring due to its wide coverage and revisit capability.
3. Assessing long-term changes in glacial lakes is important to understand the rate of glacier retreat, assess GLOF risks, and gain information about the impacts of climate change.
4. Of the 676 expanded lakes, 601 have expanded more than double, 10 have expanded between 1.5 to two times, and 65 lakes have expanded between 1.5 times.
5. Of the 676 lakes, 130 are located within India, of which 65, seven and 58 are located in the Indus, Ganges and Brahmaputra River basins respectively.
6. An elevation-based analysis revealed that 314 lakes are located in the 4,000-5,000-meter range and 296 above 5,000 meters.
7. ISRO highlighted long-term changes in the Ghepang Ghat glacial lake in Himachal Pradesh, which saw a 178% increase in size from 1989 to 2022.
8. In October, at least 40 people were killed and 76 went missing in Sikkim after the South Lhonak Lake, a glacial lake situated at 17,000 feet, burst due to incessant rains.

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