Volume Estimation of Existing and Potential Glacier Lakes, Sikkim Himalaya, India

Glacial lake outburst floods (GLOFs) are a hazard commonly reported in the glaciated terrain of the Himalaya. Glacier lakes can form if the glaciers retreat and the bottom topography overdeepens. We have adopted a technique to estimate the depth and volume of lakes using parameters such as glacier surface velocity, slope and laminar flow of ice. The technique has been automated using Python programming language. The method was applied in the Sikkim Himalaya to map potential lake sites and also to predict further expansion of existing glacier lakes. Studies were carried out for ten glaciers in the Tista river basin. The analysis suggests nine potential lake sites, including further expansion of four existing glacier lakes. To validate the results, the model lake boundary in 2001 was compared with the satellite-observed value of 2015 and field measurements made at the South Lhonak lake. The volume of the South Lhonak lake (in 2015) was estimated as 60 ± 10.8 million m³; with prolonged retreat of the glacier, the lake is likely to expand to a maximum volume of 90 ± 16.2 million m³. The above technique can provide new information to planners, leading to a more realistic approach in understanding the disaster potential of glacier lakes.