The risks of glacial lake outburst floods (GLOFs) and their effects on infrastructure and settlements downstream of such lakes have been emphasized in a number of studies on glacial lakes, the most recent of which is this one.
The Indian Space Research Organisation (ISRO) published an analysis on the expansion of glacial lakes in the catchments of Indian Himalayan river basins earlier this week using data from satellites. This study is the most recent in a string of ones on glacial lakes that have emphasized the dangers of glacial lake outburst floods (GLOFs) and how they affect the infrastructure and communities that are downstream from these lakes.
What was the result of ISRO’s analysis?
In order to evaluate changes in the glaciated environment, ISRO‘s analysis examined satellite data archives covering the previous 40 years. There has been long-term satellite imagery available since 1984, spanning the catchments of the Indian Himalayan river basins, which are distributed across India, Nepal, Tibet, and Bhutan, until 2023. Based on data from ISRO, glacial lake sizes have significantly increased.
676 glacial lakes had grown significantly since 1984 out of the 2,431 lakes larger than 10 hectares that were identified between 2016 and 2017. Of these 676 lakes, 601 had increased in size by more than two times, 10 had increased in size by 1.5 to 2 times, and 65 had increased in size by 1.5 times.
According to ISRO, 130 of the 676 lakes are located in India, specifically in the river basins of the Indus (65), Ganga (7), and Brahmaputra (58). Because of global warming, glaciers are receding faster and faster, causing these lakes to enlarge.
What causes glacial lakes to form?
The topography around glaciers is eroded and depressed by their movement. Glacier lakes form as a result of meltwater building up in these depressions as the glaciers retreat.
The formation process of glacial lakes was classified by ISRO into four main categories: ice-dammed, erosion-based, moraine-dammed, and “others.” Lakes that are created by moraine (debris like rocks and soil left behind by glaciers) and ice-dammed lakes are created when water is blocked by these materials, respectively. When depressions caused by erosion block water flow, erosion-based lakes are created.
Although glacial lakes are essential freshwater sources for rivers, they also present serious risks, particularly in the event of glacial lake outbursts (GLOFs), which can have catastrophic effects on communities downstream.
Glacier lakes burst their natural dams, releasing massive amounts of meltwater that cause abrupt and catastrophic flooding downstream. This phenomenon is known as a glacial lake flood. ISRO stated that avalanches of rock or ice could be one of the many causes of these dam failures.
How are glacial lakes monitored using satellite remote sensing technology?
Since the Himalayan region has rugged terrain, monitoring glacial lakes and their expansion is difficult. At this point, satellite remote sensing technology “proves to be an excellent tool for… monitoring due to its wide coverage and revisit capability,” according to ISRO.
According to ISRO, “satellite-derived long-term change analysis provides valuable insights for understanding glacial lake dynamics, which are essential for assessing environmental impacts and developing strategies for GLOM risk management and climate change adaptation in glacial environments.”
The majority of the glacial lake sites are inaccessible by motorized roads, according to Ashim Sattar, an assistant professor of glaciology at the Indian Institute of Technology in Bhubaneswar. In this case, our highly developed remote sensing instruments can assist us in tracking glacial lake growth and comprehending their dynamics.
How can the dangers that glacial lakes present be lessened?
The risks that Ghepan Gath Lake, which is 4,068 meters above sea level in Himachal Pradesh, poses to Sissu in the Lahaul Valley were investigated in a 2023 study that was published in the Journal of Geophysical Research. The study also modeled the effects of lowering the lake’s water levels.
Using lengthy High-Density Polyethylene (HDPE) pipes is one method of siphoning off lake water. This technique was employed in 2016 to lower the water levels in South Lhonak Lake in Sikkim by representatives of the Sikkim State Disaster Management Authority, the Department of Science and Technology, and Climate Change, among other organizations.
