Glacier Changes and Fragmentation in Birahi Ganga Basin, Garhwal Himalaya: Implications for Water Resources

Abstract

ABSTRACT Glacier changes in the Himalaya are unequivocal under changing climate, making them susceptible to water availability in the future. Given the significance of glaciers for hydrology and the dangers they pose, the current study examines the state of the only glacier (i.e., Birahi Glacier) in the Birahi Ganga Catchment (BGC), Alaknanda Basin, Uttarakhand, from 1968 to 2020. It is observed that the glacier retreated 329 ± 15 m at an average rate of 6.3 ± 0.3 m a-1, and vacated an area of ~5000 m2 a-1 from 1968 to 2020. Based on satellite images, glacier separation began in 1994, as demonstrated by the small patches exposing the bedrock. It eventually grew and detached the lower debris cover zone from the upper clean ice zone in 2019. The recent satellite image reveals that snow and ice avalanches occasionally feed the lower, disconnected debris-covered portion. At present, the lower zone with an area of 0.59 ± 0.03 km2 behaves differently than the rest of the 3.6 ± 0.06 km2 clean glacier zone. Detachment of the glacier is attributed to topography; the steep slope along the glacier’s central flow line; the upward movement of the snowline and enhanced melting in the transition zone of debris-covered ice and clean ice. During the period between 1994-2020, the glacier shows pronounced shifting of snout elevation from ~3910 to ~4000 m asl (~90 m; 2.8 m a-1) and snowline from 5143 to 5335 m asl (192 ± 17 m; 7.3 ± 0.65 m a-1). Deglaciation in BGC may pose an alarming situation for water availability downstream for drinking, agriculture, and a hydroelectric power project in the future.