ASSESSMENT OF GLACIER VOLUMES AND GLACIAL LAKE CHANGES IN THE HIMALAYAN CONTEXT

Abstract

The Satluj River originates near Manasarovar Lake and flows through Tibet, before entering India at Shipki La pass. The river flows west-southwest through the states of Himachal Pradesh and Punjab, where Beas river confluences with the Satluj river. Satluj river is fed by the glacier melt, snow melt and rain, and is considered to be the life line of Northern India, providing water for irrigation canals and a number of hydro-electric power projects like Bhakra-Nangal, Nathpa Jhakri, Kol dam and Baspa Hydel Project. The Satluj and Beas basins consist of 2018 and 469 glaciers with glacierized areas of 1433 ± 71 km2 and 499 ± 25 km2 respectively. The Parbati basin consists of 279 glaciers and has a glacierized area of 395 km2. In the future, however, the glaciers in the basin are going be altered due to fluctuations in the climate. Basin scale assessment of the glacier volume in these reservoirs is crucial to assess the future changes in mass loss, melt runoff and hydro-electric potential. Hence in this study, the volume of glaciers in Parbati, and Satluj and Beas basins of the Himalaya are estimated using the automated laminar flow model and scaling equation. Himalayan glaciers are the important source of fresh water for innumerable rivers that flow to the major rivers like Indus, Ganga and Bramaputra. To understand sustainability of this source under climate change scenario, we need proper estimate of glacier stored water. Glacier areal extent can be obtained using remote sensing techniques and numerous inventories are now providing reliable data, however depth measurements are difficult and generally obtained using scaling method. The scaling methods can provide large errors in volume estimates in the Himalaya, as limited availability of field data. This provides large uncertainties in the volume estimates. Therefore, a model based upon surface velocity, slope and laminar flow of ice was used to estimate spatial distribution of glacier depth in Parbati, Satluj and Beas Basins, Himachal Pradesh, India. The volume of the glaciers can be derived by using a laminar flow model with glacier surface velocity and slope derived from remote sensing images. Glacier surface velocities are obtained by sub-pixel correlation of consecutive year image scenes and slope is estimated from a digital elevation model at 100 m contour intervals. The thickness is initially obtained over multiple flowlines drawn on the glacier and then interpolated using thin plate spline interpolation over the entire extent of the glacier. Based on this approach, an automated modeling of glacier volume and ice thickness distribution is done in Python. Currently this model is applicable to glaciers for which uniform velocity fields are available. The thickness distribution of 298 glaciers are estimated by using the model in Satluj and Beas Basins, which cover an area of 588 ± 29 km2 and have an estimated volume of 27.5 ± 5 km3. However, large area of the basin is occupied by smaller glaciers and due to the presence of cloud cover, velocity field are not available for all glaciers. Hence, the volume of the other glaciers is computed by developing an empirical volume area scaling equation. A power law relation is derived between the area of the glaciers and volume estimates from the laminar flow model area and volume of the glacier, with scaling exponent λ = 1.2869. The total amount of glacier stored ice in Satluj and Beas basin is equal to 84 ± 15 Gt, obtained from modelled and statistically upscaled estimates of glacier volumes. The power law relation derived for Parbati basin gives a scaling exponent 1.2136. The total glacier stored water of the 155 glaciers in Parbati basin, which covers an area of 377.16 km2, is estimated as 21.07 km3.