Future water availability from the western Karakoram under representative concentration pathways as simulated by CORDEX South Asia

Employing a fully distributed hydrological model of SPHY (spatial processes in hydrology), we assessed the future water availability from a highly glacierized basin of Hunza in the western Karakoram under plausible climates as projected by the representative concentration pathways (RCPs). We successfully calibrate and validate the SPHY model for the periods 1994-1997 and 1997-2000 respectively using three high-altitude representative meteorological stations from the Water and Power Development Authority (WAPDA), Pakistan. Then, we run the model for near- (2007-2036), mid- (2037-2066), and far-future (2067-2096) climate projections under three different RCP scenario, i.e., RCP2.6, RCP4.5, and RCP8.5. Each scenario includes four high-resolution (similar to 50 km) climate experiments that are obtained from dynamically downscaling the Coupled Model Inter-comparison Project Phase 5 (CMIP5) experiments under the framework of the Coordinated Regional Climate Downscaling Experiments (CORDEX) for South Asia. The SPHY model projects a substantial increase in the ensemble mean discharges throughout the 21st century under all RCP scenarios. Such an increase is dominated by the enhanced glacier melt contribution under the high warming scenario of RCP8.5. Besides featuring a declining trend, snowmelt contribution will also remain higher than that of the historical period throughout the 21st century and under all RCPs. Our flow duration curve analysis suggests that high and median flows are projected to increase while low flows are projected to decrease in the future. These findings provide invaluable insights into the uncertainty spectrum of the water availability from the western Karakoram across envisaged future climates, which will be supportive in better managing the downstream water resources.