Hydrological Modeling of the Astore River Basin, Pakistan, by Integrating Snow and Glacier Melt Processes and Climate Scenarios

Abstract

The upper Indus River basin has large masses of glaciers that supply meltwater in the summer. Water resources from the upper Indus River basin are crucial for human activities and ecosystems in Pakistan, but they are vulnerable to climate change. This study focuses on the impacts of climate change, particularly the effects of receding glaciers on the water resources in a catchment of the upper Indus river basin. This study predicts river flow using a hydrologic model coupled with temperature-index snow and glacier melt models forced by observed climate data. The basin is divided into seven elevation zones so that the melt components and rainfall-runoff were calculated at each elevation zone. Hydrologic modeling revealed that glaciers contributed one-third of the total flow while snowmelt melt contributed about 40%; rainfall contributed to the remaining flow. Some climate scenarios based on CMIP5 and CORDEX were employed to quantify the impacts of climate change on annual river flows. The glacier retreat in the mid and late centuries is also considered based on climate change scenarios. Future river flows, simulated by the hydrologic model, project significant changes in their quantity and timing. In the mid-century, river flows will increase because of higher precipitation and glacier melt. Simulations projected that until 2050, the overall river flows will increase by 11%, and no change in the shape of the hydrograph is expected. However, this increasing trend in river flows will reverse in the late century because glaciers will not have enough mass to sustain the glacier melt flow. The change will result in a 4.5% decrease in flow, and the timing of the monthly peak flow will shift from June to May. This earlier shift in the streamflow will make water management more difficult in the future, requiring inclusive approaches in water resource management.