ICG2022-19, updated on 20 Jun 2022
10th International Conference on Geomorphology
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Glacial Lakes in the Chhombo Chhu Watershed (Sikkim Himalaya, India): Inventory, Classification, Evolution, and Potential GLOFs Assessment

Arindam Chowdhury1, Sunil Kumar De1, Milap Chand Sharma2, and Manasi Debnath3
Arindam Chowdhury et al.
  • 1Department of Geography, School of Human and Environmental Sciences, North Eastern Hill University, Shillong, India (arindam.nehu30@gmail.com)
  • 2Centre for the Study of Regional Development, Jawaharlal Nehru University, New Delhi, India
  • 3Department of Geography, Nagaland University, Lumami, India

The Sikkim Himalaya, similar to other mountain regions, has lost considerable ice cover over the years owing to the changing climatic factors leading to enlargement of glacier-fed lakes, and thus posing a potential threat to downstream communities in the mountain and Tarai (foothills) region in case of breach anytime in the future. The Chhombo Chhu watershed (CCW) of Tista basin in the Sikkim Himalaya (~694.5 km2) is located in the transitional zone between the Greater Himalayan range with a Tethyan Sedimentary Sequence, is the storehouse of number of glacial lakes covering large areas, and volume. In order to evaluate the critical glacial lakes, we mapped the changes between 1975–2018 and assessed their dynamics based on manual analysis of medium to high-resolution optical images for the years 1975, 1989, 2000, 2010 and 2018, respectively and verified during field surveys. Results show that the number of lakes has increased from 62 to 98, and its total area expanded significantly by ~34.6 ± 5.4%, i.e., from 8.5 ± 0.2 km2 in 1975 to 11.4 ± 0.6 km2 by 2018, at an expansion rate of 0.8 ± 0.1% a−1. It is interesting to note that these lakes expanded faster during 2010–2018 (+1.18 ± 2.0% a–1), i.e. in the recent decade, compared to previous years such as +1.02 ± 1.1% a–1 in 1975–1988, +0.54 ± 1.3% a–1 in 1988–2000 and +0.20 ± 1.6% a–1 in 2000–2010. Lake outburst susceptibility result reveals that a total of twenty-seven potentially dangerous glacial lakes exist in the CCW; 5 have a status of ‘high’ outburst probability, 17 ‘medium’ and 5 ‘low’. Accelerating increasing long-term average annual trend of temperature (+0.283 °C a−1; 1975–2013) at 95% confidence level also supports the glacier area lost (–0.66 ± 0.1% a–1), and lake area enlargement trend (+0.80 ± 0.1% a–1) between 1975 and 2018, indicating heightened impact of climate change in the CCW of the Sikkim Himalaya.

How to cite: Chowdhury, A., De, S. K., Sharma, M. C., and Debnath, M.: Glacial Lakes in the Chhombo Chhu Watershed (Sikkim Himalaya, India): Inventory, Classification, Evolution, and Potential GLOFs Assessment, 10th International Conference on Geomorphology, Coimbra, Portugal, 12–16 Sep 2022, ICG2022-19, https://doi.org/10.5194/icg2022-19, 2022.