Geo-Spatial Dynamics of Snow Cover and Hydro-Meteorological Parameters of Hunza Basin, HKH Region, Pakistan

Snow cover dynamics play an important role in the hydrological characteristics of Upper Indus Basin (UIB) of Pakistan in terms of seasonal accumulation and depletions. The current study has been carried out to understand the snow cover dynamics, hydrological regime and their inter-relationships. Remote sensing satellite data of Moderate Resolution Imaging Spectro-Radiometer (MODIS) for the period 2000–2016 along with hydro-meteorological parameters was used to study the spatio-temporal changes in snow cover of Hunza basin. Snow cover dynamics were analyzed through temporal analysis of snow cover and its association with hydro-meteorological parameters using Pearson correlation, Principle Component Analysis (PCA) and elevation-based sub zones. The study concluded that 25–40% of the basin area is covered by glacier. Snow covered area may reach up to 90–95% of the basin area due to accumulation of seasonal snow. Hydro-meteorological correlation matrices showed highly significant correlation (R = 0.78) among maximum and minimum temperatures and river runoff while no correlation was observed between river runoff and rainfall (R = –0.03). A highly significant negative correlation was found for River runoff and Hunza mean Snow covered area (R = –0.87). The negative coefficient value shows that river runoff increases with snow cover melting when temperature increases. At sub-altitudinal zones level, river runoff has high negative correlation with snow cover at high altitude zones (Zone 2, 3) (R = –0.84, –0.86) while at lower altitude (Zone 1) there was a moderate correlation (R = –0.6) between snow cover and river runoff. This study reveals that river discharge in Hunza basin is closely associated with its snow cover dynamics. River runoff is associated with basin’s snow melt phenomenon triggered by seasonally increasing temperatures. River discharge increases with active snow melting with start of summer during the months of April and May. Snow melt starts first at lower altitude zones followed by higher elevation zones with higher vertical glacial deposits.