The Himalayas, a majestic mountain range nicknamed the “Third Pole” for its vast reserves of freshwater ice, faces a growing threat. Climate change is causing glaciers in this region to retreat at alarming rates. This melting isn’t just shrinking the glaciers themselves; it’s also leading to the formation of new glacial lakes and the expansion of existing ones.
A Double-Edged Sword: The Rise of Glacial Lakes
These glacial lakes, while initially appearing beneficial by providing additional freshwater for rivers, pose a significant danger: Glacial Lake Outburst Floods (GLOFs). When the natural dams containing these lakes – often composed of moraine or ice – fail, they unleash massive torrents of water in sudden and devastating floods downstream. These dam failures can be triggered by various factors, including avalanches, extreme weather events, and other environmental changes, according to latest data from the Indian Space Research Organisation.
CHALLENGES AND SOLUTIONS: MONITORING FROM SPACE
Studying these glacial lakes nestled within the rugged Himalayan terrain is a complex task. Here’s where satellite technology steps in and offers a powerful solution. Satellites provide a valuable tool for monitoring and tracking these lakes due to their wide coverage and ability to revisit the same areas regularly. By analyzing data collected by satellites over the past 3-4 decades, scientists can gain valuable insights into the changes happening in the Himalayas.
A CLEAR PICTURE EMERGES: THE ALARMING RATE OF GLACIAL RETREAT
- Looking at satellite imagery from 1984 to 2023, researchers have observed a significant increase in the size of glacial lakes in the catchments of Indian Himalayan rivers. Here are some key findings:
- A staggering 676 out of 2,431 lakes larger than 10 hectares identified in 2016-17 have grown noticeably since 1984.
- Notably, 130 of these expanding lakes are located in India, spread across the Indus, Ganga, and Brahmaputra River basins.
- A concerning 89% (601 lakes) have more than doubled in size.
ELEVATION MATTERS: HIGHER LAKES, FASTER EXPANSION
The analysis also revealed a correlation between elevation and the rate of lake expansion. Most of the expanding lakes are situated at high altitudes:
- 314 lakes lie between 4,000 and 5,000 meters elevation.
- An additional 296 lakes are positioned above 5,000 meters.
DIFFERENT TYPES OF GLACIAL LAKES
There are four main categories of glacial lakes based on how they form:
- Moraine-dammed lakes: These are formed when water gets trapped behind deposits of rocks and debris left by glaciers (moraine).
- Ice-dammed lakes: Water gets dammed by glacial ice in these lakes.
- Erosion lakes: These lakes form in depressions carved out by glacial erosion and subsequently filled with meltwater.
- Other glacial lakes: This category encompasses lakes formed by less common processes.
Of the expanding lakes, the majority fall into the Moraine-dammed category (307), followed by Erosion (265), Other (96), and Ice-dammed (8).
A CASE STUDY: GHEPANG GHAT LAKE – A STARK EXAMPLE
One example that exemplifies the rapid expansion of glacial lakes is the Ghepang Ghat glacial lake in Himachal Pradesh, India (Indus River Basin) situated at 4,068 meters. Between 1989 and 2022, this lake’s size increased by a staggering 178%, growing from a mere 36.49 hectares to a much larger 101.30 hectares. That translates to a growth rate of nearly 2 hectares per year!
IMPORTANCE OF LONG-TERM MONITORING: PLANNING FOR THE FUTURE
Long-term analysis of satellite data provides crucial insights into the dynamics of glacial lakes. This information is essential for understanding the environmental impacts of glacial retreat, such as increased risks of GLOFs. It empowers communities living downstream to develop effective strategies for managing GLO.