Monitoring of moraine-dammed lakes: a remote sensing-based study in the Western Himalaya

Monitoring of lakes in glaciated terrain in the Himalayan region has been recognized as one of the priority areas especially after the Kedarnath disaster. Among all types of glacial lakes, moraine dammed lakes (MDLs) are the most important from disaster point of view. Remote sensing plays a significant role in view of availability of unbiased repeated data on the expansion or contraction of MDLs located in rugged terrains of the Himalaya. Monitoring of two MDLs, associated with Katkar and Gepang-gath glaciers in Zanskar and Chandra sub-basins respectively was done using satellite images of 1965, 1976, 1989, 2001, 2006-07, 2012 and 2014. Survey of India (SOI) topographical maps of 1962 were also referred to monitor the respective glaciers lakes. SOI maps show the presence of only one lake associated with Gepang-gath glacier. Areal extent of the MDLs had increased from 21 to 57 ha between 1965 and 2014, and from 27 to 80 ha between 1962 and 2014 for the Katkar and Gepang-gath glaciers respectively. Increase in peak discharge of the two lakes was also estimated using different empirical models in case of outbursts of these lakes. The lake outburst probability for both these lakes was found to be very low (less than 1%), however, possibility of outburst of lakes due to natural calamity like cloud burst, landslide or earthquake cannot be ignored. The rate of retreat of these two glaciers was observed to be high due to the presence of MDLs in comparison to surrounding glaciers in the valley.