Comparative assessment of spatiotemporal variability in cryosphere and hydro-climatic regime of the Hunza, Astore and Shigar Basins (Hindukush-Karakoram–Himalaya Region) in Pakistan

The study is based on the climate change impacts on the snow cover area (SCA) and hydrologic regime of the Hunza, Astore and Shigar River basins located in the Himalayan and Karakoram Ranges of the Upper Indus Basin (UIB). The study utilized the daily river discharge data along with the temperature and precipitation records of the meteorological stations for three basins spanning 2000-2018. The Moderate Resolution Imaging Spectroradiometer (MODIS) snow images were used to investigate the basin-wide and altitudinal zone-wise (z1, z2 & z3) changes in the SCA for the same years. The Modified Mann Kendall (MKK) test and Sens’s slope estimator (at 5% significant level) were used to analyze the annual and seasonal (winter & spring, pre-monsoon, and monsoon) changes in trends of daily temperature, precipitation, river discharge and SCA. The Kendall rank, Spearman and Pearson correlation tests were performed to investigate the annual and seasonal correlation between the hydroclimatic variables and SCA. Basin-wide annual and seasonal temperature trends indicated warming in the three basins. A decline in basin-wide SCA in the three basins with the highest change (τ= -0.06) on annual basis for the Hunza basin has been computed. The overall correlation results revealed a large snowmelt contribution to their respective rivers discharge during the pre-monsoon season (April-June). We conclude that in these high-altitude river basins future variations in temperature and SCA could significantly affect the streamflow timing and volume into the Tarbela Reservoir.