Dynamics of Hamtah Glacier, Lahaul & Spiti district, Himachal Pradesh

Understanding the glacier dynamics is significant for understanding the response of the glacier to the changing climate, i.e., determining how the glaciers change over time in response to a changing climate. It is well known that velocity of the glacier is a function of thickness and gradient of the glacier bed. In addition, the glacier velocity also depends on the availability of the water at the bottom as the basal sliding is considered as the most important factor affecting the dynamics of Himalayan glaciers. In order to understand the impact of changing glacier mass balance and the availability of melt water at the glacier bed, the glacier dynamics of Hamtah glacier, a small valley glacier in Chenab basin, Lahaul & Spiti district, Himachal Pradesh, has been studied. For this purpose the horizontal component of flow movement has been measured, during 2000-01 to 2005-06, using the stake network fixed for the assessment of annual mass balance. The highest glacier flow velocities were recorded in the highest elevation zones whereas the least flow velocities were observed near the glacier snout. The annual horizontal component of flow velocities recorded successive decline from 2000-01 to 2003-04 with marginal upward trend in 2004-05, followed by decline in 2005-06. This variation in horizontal component of flow velocity was correlated with the mass balance recorded during the observation period. In addition, the annual and summer horizontal component of flow velocity was also compared to comprehend the effect of the increase in water availability at the glacier bed. It has been observed that the annualized summer flow velocities (Um*12) and the annual flow velocities (Ua) deduced from field measured summer flow and annual flow respectively show considerable variations, including during different observational years.