Snowmelt Runoff Modelling under Projected Climate Change Patterns in the Gilgit River Basin of Northern Pakistan

摘要

Pakistan is home to three of the world's largest mountain ranges in the Upper Indus Basin (UlB), where the majority of Pakistan's water resources are located: the Himalayan, Karakorum, and Hindu-Kush. This work estimated the (snow+glacier) and rainfall runoff from one of the major tributaries, the Gilgit River, nestled within the UIM of Pakistan. The snowmelt runoff model (SRM) derived by the cryospheric data from the MODIS (moderate resolution imaging spectroradiometer) was employed to predict the daily discharges of the Gilgit. The SRM was successfully calibrated, and the simulation was undertaken from 2005 to 2010, with a coefficient of model efficiency ranging from 0.84-0.94. The average contributions of (snow+glacier) and rainfall to the stream flows of the Gilgit from 2001-10 were 78.35% and 21.65%, respectively, derived from the SRM. The representative concentration pathways (RCP) 4.5 and 8.5 scenarios of the Intergovernmental Panel on Climate Change (IPCC) AR5 were used to investigate the effects of the changes in temperature on climate of the Gilgit catchment. Under the RCP 4.5 scenario, the air temperature of Gilgit will increase by 3(omicron)C, whereas the increase in precipitation will be minor. Under the RCP 8.5 scenario (overshooting scenario), air temperature will increase by 10.7(omicron)C, whereas precipitation will decrease between 2010 and the end of the 21(st) century in the Gilgit catchment. The application of the RCP 4.5 and 8.5 mean temperature scenarios in the SRM suggested that with increases in mean temperature of 3.02(omicron)C and 10.7(omicron)C, respectively, the average annual runoff in the Gilgit will increase by 67.03 and 177.5%, respectively, compared with the observed runoff by the end of the 21(st) century. This increased surface runoff from snow/glacier melt can potentially be utilized by planning new storage areas at appropriate locations to harness additional water.