Effect of climate and socioeconomic changes on future surface water availability from mountainous water sources in Pakistan's Upper Indus Basin

Pakistan is highly dependent on water resources from the mountainous regions of the Upper Indus Basin (UIB), especially for irrigation. An evaluation framework was developed and applied in this study to understand the variability in surface water availability to agricultural and domestic sectors across various future climate and socioeconomic pathways in five catchments within the UIB (Astore, Gilgit, Hunza, Shigar, and Shyoke). A planning tool named Water Evaluation and Planning (WEAP) was used to understand the dynamics of past and future water demands for multiple future scenarios. We combined three different climate scenarios (representative concentration pathways) with socioeconomic scenarios (shared socioeconomic pathways) of economic development and population and local agricultural land development pathways. The results indicate that the external driving forces of climate change and socioeconomic growth will cause a discrepancy between the supply and demand of water resources in regions with higher socioeconomic growth, particularly those with agricultural development as the dominant external factor. Among the five catchments within the UIB, Astore and Gilgit face a water shortfall in all future scenarios, whereas Shyoke will encounter water deficiencies only in the case of agricultural land development. We also demonstrated that the impact of climate change is markedly different in Astore and Gilgit. Over Astore, the impact of precipitation will control the unmet water demands by increasing winter streamflow whereas over Gilgit non-climatic factors, such as population and agricultural growth, will control future unmet water demands.