Hydrological characteristics of Sutri Dhaka glacier catchment in the western Himalaya

The Himalaya is a massive cryospheric reserve, which provides a significant amount of fresh water to major Asian rivers like the Indus, Ganges, Brahmaputra, etc. Climate-induced cryospheric change is one of the major worldwide concerns, particularly in the Himalaya. Meltwater from glaciers and snow stabilises the downstream river runoff, and it buffers against drought during the driest years to some extent. The hydrological impact due to climate change in the high Himalayan catchments is potentially amplified by the shrinkage of snow and ice reserves. Therefore, it is important to analyse the potential hydrological changes at catchment to regional scales in the Himalaya. Hydrological changes at the regional scale are mainly determined by glacier catchment scale hydrology. Presently, understanding the regional scale discharge in the Himalaya suffers from large uncertainties, and one major source is the lack of glacier catchment scale hydrological understanding. Motivated by the above, here we are studying the glacio-hydrological characteristics of the Sutri Dhaka Glacier (debris-free glacier) catchment, which is located in the Chandra basin, western Himalaya. The glacierised area is ~20 km², and the total catchment area is ~45 km².

To the glacier catchment, we are applying an hourly timescale glacio-hydrological model to simulate discharge and the corresponding hydrograph components from 1980 to 2022. We also obtained extensive long-term field measurements of glacier mass balance, meteorological parameters, and discharge for the ablation season of 2016 to 2022 (with some gaps). These field data are used to calibrate the model parameters using a Bayesian framework and validate the simulated discharge and glacier mass balance. The simulated discharge variability from the diurnal to inter-annual time scale matches with the observations with reasonable accuracy (R²>0.75). Also, the model is able to capture the strong seasonality of the diurnal discharge amplitude, which has a direct relation to the storage-release properties of the glacier. Particularly, the diurnal discharge variability from the Himalayan glacier catchment is not well explored in the literature. We have also computed the associated uncertainties in the model as we as in the observations. Our present analysis will help to improve the existing process-based understanding of the glacier catchment scale discharge from the glacierised Himalayan region.