Future prediction of existing glacial lake’s size in the Himalaya by Markov model and glacial surface topography

ABSTRACTThe number and size of glacial lakes are increasing at a higher rate in the Himalaya because of rapid global warming. These lakes are the potential future zones of glacial lake outburst flood (GLOF) risks to the downstream; hence, regular monitoring along with future prediction in lake size must be done to find possible zones of future risks. This research focuses on the future prediction of regional-scale glacial lake size in the entire Himalayan mountain range. Here, we used Landsat TM and OLI images, Google Earth imageries, Cartosat DEM, and SRTM DEM, and used some techniques: average lake size change rate, Markov model and glacial surface topography to extract glacial lake size change and future prediction of lake size. A total of 9675 individual glacial lakes were noticed during the study period (1990-2020), out of which the lakes present constantly throughout the study period (with size >0.01 km2) were added in this study. Additionally, out of 1646 numbers of constantly present lake throughout the study period, 751 moraine dam lakes were taken for the future prediction of lake size change using the Markov model. A total of 191, 167 and 393 lakes were predicted as increase at a higher rate (Fast increase-FI), decrease at a lower rate (slow decrease-SD) and increase at a slower rate (slow increase-SI), respectively in Markov model. Besides, glacial topography was also used as an indicator of future lake size change taking a total of 457 number of lakes; thus, a total of 94, 123 and 240 lakes out of 457 were identified as lower, medium and higher prone to unconnected, respectively. Here, the common future predicted growth lakes from these two models were taken as critical lakes. The critical lakes are mostly concentrated in eastern Himalaya (227) followed by central (195) and western Himalaya (21)