Assessing snow and glacier melt contributions using conceptual modelling approach in the Upper Indus Basin

The Hindukush-Karakoram-Himalaya (HKH) region, a vital water source for over 800 million people across the Indus, Ganges, and Brahmaputra river basins, relies heavily on the continuous freshwater supply derived from its extensive snow and ice reservoirs. Estimating snow and glacier melt in this complex hydrological setting poses challenges, particularly concerning the intricate interactions among various hydrological processes. Conceptual models have experienced exponential growth in hydrological modelling due to their cost-effectiveness in computational requirements while maintaining the accuracy of simulated streamflow. Snow and glacial melt modules are generally integrated into the hydrological model to accurately represent the intricate interactions among snow, glaciers, and precipitation in mountainous catchments. The present study focused on incorporating snow and glacier modules using a degree-day factor approach into a four-parameter conceptual Hydrological model GR4J. The model will be calibrated and validated in the Upper Indus basin's glaciated sub-basins, Astore and Hunza. The study will use the ERA5 Reanalysis-based precipitation, temperature for meteorological forcing and GloFAS discharge data used as observed streamflow. The results obtained will help understand the applicability of conceptual hydrological models in capturing hydrological processes and the potentiality of the reanalysis data in the absence of observed data and will give an idea about the snow and glacier melt contributions. Looking ahead, the study will be further helpful in studying the impacts of climate change in assessing future water availability under different scenarios.