From Orbit to Earth: ISRO's Contributions to Understanding Himalayan Glacial Shifts

The Himalayas, often referred to as the Third Pole because of their extensive ice and glacier coverage, are highly sensitive to changes in the global climate. These shifts impact both the mountain’s physical structure and the communities living nearby.

Research indicates that since the Industrial Revolution began in the 18th century, glaciers worldwide have been retreating (shrinking) and thinning at unprecedented rates.

This retreat leads to the formation of new glacial lakes and the expansion of existing ones in the Himalayas. These lakes, which are created from the meltwater of glaciers, play a crucial role by feeding freshwater into nearby rivers.

However, these lakes can also pose significant threats, such as Glacial Lake Outburst Floods (GLOF’s), which can devastate downstream areas.

GLOF’s occur when the natural barriers or dams , composed of moraine (rock piles and debris) or ice, that confine these lakes fail, unleashing sudden and massive floods.

Triggers for these natural dam failures include rock or ice avalanches (snowslides), severe weather conditions, and other environmental factors.

Monitoring and studying the development and expansion of glacial lakes in the challenging terrains of the Himalayas is difficult. However, satellite remote sensing offers a practical solution, allowing for the extensive and repeated surveying of these regions. Analyzing the evolution of these lakes is essential for understanding glacier melt rates, assessing flood risks from lake outbursts, and comprehending the broader impacts of climate change.

Satellite data spanning the last three to four decades reveals significant changes in glacier-covered regions. Analyzing long-term satellite images of river basins in the Indian Himalayas from 1984 to 2023, noticeable alterations in glacial lakes have been observed.

On April 22nd, ISRO shared via their X handle that out of 2,431 lakes each larger than 10 hectares (approximately 24.71 acres) identified in 2016-17, 676 have shown considerable growth since 1984. Specifically in India, these expanding lakes include 65 in the Indus basin, 7 in the Ganga basin, and 58 in the Brahmaputra basin.

Further details reveal that 314 of these lakes are located at heights between 13,123 and 16,404 feet (4,000 to 5,000 meters), while 296 lakes are found at elevations exceeding 16,404 feet (5,000 meters).

Satellite data from the past few decades has been crucial in tracking the changes in regions covered by glaciers. Long-term observation of the Indian Himalayan river basins from 1984 to 2023 shows significant shifts in glacial lakes.

From the data analyzed, out of 2,431 lakes each larger than 10 hectares (about 24.71 acres) recorded in 2016-17, growth trends are as follows:

● 601 lakes (89%) have more than doubled in size

● 10 lakes have grown by 1.5 to 2 times

● 65 lakes have increased by 1.5 times

Glacial lakes can be categorized into four primary types based on their formation:-

● Moraine-dammed lakes (contained by rock and debris piles)

● Ice-dammed lakes (contained by ice)

● Erosion lakes (formed in depressions caused by erosion)

● Other types of glacial lakes

Among the 676 expanding lakes, the majority are Moraine-dammed (307 lakes), followed by Erosion (265 lakes), other types (96 lakes), and Ice-dammed (8 lakes).

One notable example is the Ghepang Ghat glacial lake in the Indus River Basin, Himachal Pradesh, India. Positioned at an elevation of 13,352 feet (4,068 meters), it has seen substantial growth. From 1989 to 2022, its size increased by 178%, from 36.49 hectares (about 90.13 acres) to 101.30 hectares (about 250.37 acres). This growth translates to an average annual increase of about 1.96 hectares (roughly 4.84 acres).

This satellite-based monitoring is essential for understanding the dynamics of glacial lakes, assessing environmental impacts, and planning strategies to mitigate risks from glacial lake outburst floods (GLOFs) and adapt to climate changes in regions with extensive glaciers.

Girish Linganna
Defence & Aerospace Analyst
Mobile +91 9845099196

(The author Girish Linganna of this article is a Defence, Aerospace & Political Analyst based in Bengaluru. He is also Director of ADD Engineering Components, India, Pvt. Ltd, a subsidiary of ADD Engineering GmbH, Germany. You can reach out to him at: girishlinganna@gmail.com)