Interpretation and collation of field and remote sensed data in Indian Himalayan Glaciers

Indian Himalayan glaciers beset in rugged terrain and at an higher altitudes thus restricting approach to glaciers for mapping, observations and validation of remote sensed data and paucity of freely available topographic maps has added up source of errors. The scientific documentation of Himalayan glaciers initiated as part of World glacier monitoring programme of then International des glacier Commission in 1905,wherein glaciers of Karakorum, Lahaul Himalaya, erstwhile United Province area and Sikkim Himalayas were mapped, established photographic stations and cairns(Rec.GSI 35) Aerial photographs of the glaciers were obtained during sixties as part of modern survey of Indian territory which translated on toposheets. The period of aerial photography was Oct-Dec i.e. onset of winter in the higher reaches of Himalaya thereby most of the glaciers terminus and proglacial area was snow-covered. With the advent of satellite remote sensed data in seventies the glaciers studies got impetus (Vohra et al.1981) Data generated over the years by different agencies based on varied sources-cartographic/toposheets, field based and remote sensing has lead to redesign the methodology for accuracy of data with minimal errors. The methodology adopted by Geological Survey of India was preparation of detailed maps of the frontal part of glacier, establishment of photographic stations and 'cairns 'followed by repetitive monitoring of these glaciers over a period of time. Later studies necessitated interpretation of aerial photographs to study geomorphology of glacier and its proglacial area as the area was snow-covered and redemarcate snout on translated toposheet. Similarly, the remote sensed data was interpreted due to individual pixel size variation (73 m to 0.5m, present day) over a period of time. Interpretation of aerial photographs(1960-62,1978) for glacier studies is restricted to GSI, therefore the interpretations based on Survey of India toposheet(1960-63) has an inherent error which is duly reflected in the estimation of glacier recession/mass balance especially as in the case of Shaune garang glacier(Mukherjee &Sangewar,1997),Panchi Nala I(Patiseo),II(Shukla et al.2010) Gangotri glacier(Sangewar,1997). Glacier inventory of Himalayan glacier, mainly based on field data(Sangewar&Shukla,2009) and on remote sensed data(SAC/ISRO,2011) shows a wide variations in the number of glaciers(Gl no.) as well as glacierised area(sq km) viz. Chenab basin-Gl no.1278(GSI)/1569(SAC), Glacierised area 3058.99(GSI)/4016.91(SAC),Beas basin-Gl no.277(GSI)/335(SAC),Gl area-599.06(GSI)/698.06(SAC),Ravi basin-Gl no.172(GSI)/253(SAC),Gl area-192.75(GSI)/319.16(SAC),Bhagirathi basin-Gl no.238(GSI)/172(SAC),Gl area-755.43(GSI)/992.67(SAC) etc. Considering, wide variations in studies based on field based techniques and remote sensing method an approach is recommended as part of "Report of the Study Group on Himalayan Glaciers-2011" wherein over a selected glacier(s) integrated studies for glacier recession and mass balance by field and remote sensing techniques proposed. Thus the 'evolved model' can be extrapolated to other glaciers in a basin and on regional scale.