Rock glaciers of the semi-arid northwestern Himalayas: distribution, characteristics, and hydrological significance

The northwestern (NW) Himalayan region, which has a semi-arid to dry climate, is climatologically very fragile and susceptible to future drought conditions. The limited agricultural land and its dependence on the diminishing meltwater reserves have severely impacted local communities. Even though indigenous peoples that rely on glaciers and snowmelt have evolved peculiar water management and agro-pastoral techniques, their fate in the future will heavily rely on the climatically more resilient rock glaciers (RGs). Despite their significance, comprehensive research on this valuable resource is sparse. The present study focusing on the NW Himalayas (-222,343 km2) has shown the existence of -3082 intact RGs covering an area of -1466.6 km2 with a mean specific density of 1.7 % Following the classification of the International Permafrost Association, out of these 3082 RGs, 1205 were glacier connected (GC), 1043 talus connected (TC), 568 debris-mantled slope-connected (DC), and 266 glacier-fore-field connected (GFC) RGs. We have estimated the water volume equivalents (WVEQ) of these RGs by assuming that the average amount of ice in TC and DC was 20 % (lower range), 30 % (middle range), and 40 % (higher range). For GC and GFC RGs, it was 40 % (low range), 50 % (middle range), and 60 % (upper range). The GC RGs had an estimated WVEQ of 12.69 km3 to 19.04 km3, whereas the GFC RGs had 2.26 km3 to 3.40 km3 of WVEQ. The TC RGs hold 0.66 km3 to 1.32 km3 WVEQ, and the DC RGs store 2.30 km3 to 4.60 km3 WVEQ. The total WVEQ storage varies from 17.91 km3 (lowest) to 28.36 km3 (highest), corresponding to 17.91 to 28.36 trillion liters. Considering all of this, we propose that the hydrological significance of these water resources in deglacierizing Himalayas will increase over the coming decades, hence calling for multidisciplinary systematic investigations, notably their hydrology and reliable water volume estimates contained in them.