Inventorying rock glaciers in the Western Himalaya, India, and assessing their hydrological significance

Abstract

Rock glaciers, important indicators of mountain permafrost, play a critical role in mountain hydrology. Despite their significance, comprehensive studies on delineation, characterization, and hydrological potential of rock glaciers in the Himalayan region are currently in the incipient stages. In this study, we present a detailed rock glacier inventory for the western Himalayan regions of Jammu-Kashmir and Trans-Himalayan Ladakh, spanning six mountain ranges. Using optical satellite images from Google Earth and adhering to guidelines of the International Permafrost Association, we identified a total of 5807 rock glaciers, including 5292 intact and 515 relict. The delineated rock glaciers cover an area of 712 km2, with an average size of 0.12 km2. The Zanskar range hosts the highest number of rock glaciers (n = 1763), while the Pir Panjal range has the lowest (n = 317). Out of total 5807 rock glaciers, 3754 (64.6 %) are talus-connected, 638 (11 %) are glacier-connected, 630 (10.9 %) are debris-mantled slope-connected and 785 (13.5 %) are glacier-forefield connected. The rock glaciers are located at elevations between 3190 m and 5753 m asl, predominantly facing north, northeast, or northwest (62.7 %). The Mean Annual Air Temperature of the rock glaciers ranges from −9.4 °C to 3.9 °C (mean −3.7 °C) and annual precipitation ranges from 57 mm to 970 mm (mean 286 mm) with warmer rock glacier locations being systematically wetter climates – a trend similar to that observed for mountain glaciers in the study area. An estimated 13.7 km3 of water is stored within the mapped rock glaciers, making them an important hydrological reservoir in this ecologically sensitive area. The presence of rock glaciers across the study area also indicates widespread periglacial permafrost and the present inventory of rock glaciers may be a useful baseline for the future research of the response of permafrost, including rock glaciers, to climate change.