Bangalore: A satellite-based study has indicated that a huge glacial lake has formed atop the Himalayas in Sikkim with a "very high" potential for it to burst and create devastation downstream. Analysis of satellite data has revealed that the lake has formed at the snout of South Lhonak glacier, that is about 7,000 meters high on the mountain in the northeastern state. The lake, bounded only by loose soil and debris, could cause havoc downstream if it ruptures, according to scientists at the National Remote Sensing Centre (NRSC) in Hyderabad.
In a report published in the latest issue of the journal Current Science, NRSC researchers Babu Govindha Raj and co-workers say the glacial lake is about 630 meters wide and 20 meters deep. It covers an area of 98.7 hectares and contains 19.7 billion liters of water. A sudden outburst "can create devastating floods downstream," they warn, adding that the probability of this happening "is very high".
They however note this is only their preliminary assessment and more field studies are required to confirm the hazardous potential of this high altitude lake. Data from the American Landsat, CORONA and Terra satellites besides imageries from India's own Resourcesat-1 satellite were used to estimate the size of the shrinking Lhonak glacier and the growth of the glacial lake at different times between 1962 and 2008.
Based on this study the scientists estimate that the Lhonak glacier had receded 1.9 km between 1962 and 2008. The glacial lake that was initially a small body of water in 1962 grew in size with accumulation of melt water. The NRSC scientists say that the lake is still attached to the snout of the glacier but is expanding in area due to the glacier retreat.
"The rate of growth of the lake indicates possible developments of the hazard situation," the report says. As Himalayan glaciers are retreating fast, it is necessary to make an inventory of glacial lakes and set up an early warning system for lake outburst floods in vulnerable areas, they say.
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