Estimates of Glaciers Mass Balance and Volume in Baspa Basin, Indian Himalaya

Monitoring changes in glacier mass distribution is crucial for evaluating the availability of meltwater for downstream communities and managing the reservoir storage, particularly in the Himalayas, where many reservoirs support hydropower generation and irrigation. This study assesses the mass and volumetric changes of 42 glaciers in the Baspa basin. Mass changes were estimated using a temperature-index melt model, with inputs from weather records at the Chitkul meteorological station, while volume changes were derived using the Highthim model, based on surface velocity, slope and ice flow. The meteorological data was collected over 9 years (2014-2022) from Chitkul, located at an altitude of 3,423 m, by the Bhakra Beas Management Board in Chandigarh. The study estimates annual mass balance over the observation period, showing variations at the glacier scale, ranging from + 0.44 +/- 0.33 to -1.47 +/- 0.33 m.w.e., with a total ice loss of 3.8 megatons (3.8 x 10(6) m(3)). Regionally, the glaciers experienced an average mass loss of approximately -0.76 m.w.e. per year. A correlation analysis of the estimated mass balance of Naradu glacier with in situ observations (2014-2017) showed a strong correlation (r(2) > 0.90), with an error of +/- 0.35 m.w.e. The volumetric analysis revealed surface ice velocities of glaciers ranging up to 68 m per year, with a total ice volume of 22.45 gigatonnes water equivalent (Gt w.e.)in the basin. Individual glacier volumes range from 0.14 to nearly 5 Gt w.e. Comparisons with national and global mass balance studies indicate that glaciers in the Baspa basin are in retreat. This trend suggests future challenges for local communities regarding water supply for various socio-economic purposes and hydropower generation. It highlights the potential for artificial recharge structures as a solution for the sustainability of people in the valley.