ABSTRACT
Results of snow cover mapping, its seasonal variability and integration with meteorological data sets are presented from Dokriani and Chorabari glacial catchments of higher Himalaya in Garhwal ranges of Uttarakhand. Long-term snow cover variability has emerged as an important criterion to highlight climate change and availability of melt water in river basins. Seven years’ remote sensing data from 2009–2011 and 2013–2016, from satellite series (Landsat 5, 8 and Sentinel 2), is utilized to map the areal extent of snow cover and topographical controls. Differentiation between snow-covered and non-snow-covered areas as well as identification of snow by automatic and visual interpretation is carried out by Normalized Difference Snow Index (NDSI). In cloud-covered as well as shadowed regions, the band ratio method has helped in demarcation of snow-covered areas. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) is used for extraction of topographical details (elevation, aspect and slope). Elevation zones were obtained with the difference of 500 m asl. Snow cover changes below the elevation of ~5000 m asl, while the 5000–5500 m asl zone plays a pivotal role in sustaining the maximum snow-covered area. From the aspect point of view, Dokriani has east to west while Chorabari has north to south orientation. Furthermore, these catchments were divided into eight directional classes: N, NW, NE, S, SE, SW, E and W. Slope categories were identified and divided with 10° difference. Minimum variability of snow cover lies below 10°, while maximum is seen between 20° and 50°. Temperature data was obtained from automatic weather stations (AWSs) at different elevation zones in both the catchments. Isotherms ~ 0, 1, and 2°C were computed by an extrapolation method using temperature lapse rate (TLR) and analysed. The methodology developed during the study is efficient, reliable and can be applied to other comparable areas.
