Assessment of watershed hydrological responses under climate change scenarios: a case study of Hunza River basin

Climate change significantly affects the sustainability of water resources in the river watershed. The irregular precipitation distribution pattern, changes in the seasonal flows of rivers, and enhanced glaciers and snowmelt have been observed in recent decades across the watersheds of rivers in high mountains, including the Karakoram region. Comprehending the effects of climatic changes on watershed hydrology is essential for ensuring the well-being of human society, the sustainability of ecosystems, and the balance of environmental processes. These changes in precipitation, temperature, and glacier extent might result in diversified impacts on river flows in the glaciered basins of Pakistan. In this study, four global climate models (GCMs) under the shared socioeconomic pathways (SSP) 2-4.5 and 5-8.5 scenarios, from the Coupled Model Inter-comparison Project Phase 6 (CMIP6), for temperature and precipitation changes have been used. These GCMs data were input into the University of British Columbia Watershed Model (UBCWM) to forecast the streamflow for the near future (2025-2050) as compared to a baseline period (2002-2009). In this study, changes in glacier extents were also assessed. Results of the glacier extents revealed that satellite images underestimate glacier extents by an average of 18.0% compared to ground survey measurements. Maximum streamflow was generated under SSP5-8.5 with SDC, followed by SSP2-4.5 of GCMs. Among the four GCMs, ACCESS-CM2, MPI-ESM1-2LR, and INM-CM5 are predicting better results than the BCC-CSM2-MR. This study provides detailed insights into the performance of climatic models, offering a foundation for developing adaptation strategies and guiding climate change policymaking in the region.