Abstract
Upper Indus Basin (UIB) supplies more than 70% flow to the downstream agricultural areas during summer due to the melting of snow and glacial ice. The estimation of the stream flow under future climatic projections is a pre-requisite to manage water resources properly. This study focused on the simulation of snowmelt-runoff using Snowmelt-Runoff Model (SRM) under the current and future Representative Concentration Pathways (RCP 2.6, 4.5 and 8.5) climate scenarios in the two main tributaries of the UIB namely the Astore and the Hunza River basins. Remote sensing data from Advanced Land Observation Satellite (ALOS) and Moderate Resolution Imaging Spectroradiometer (MODIS) along with in-situ hydro-climatic data was used as input to the SRM. Basin-wide and zone-wise approaches were used in the SRM. For the zone-wise approach, basin areas were sliced into five elevation zones and the mean temperature for the zones with no weather stations was estimated using a lapse rate value of −0.48 °C to −0.76 °C/100 m in both studied basins. Zonal snow cover was estimated for each zone by reclassifying the MODIS snow maps according to the zonal boundaries. SRM was calibrated over 2000–2001 and validated over the 2002–2004 data period. The results implied that the SRM simulated the river flow efficiently with Nash-Sutcliffe model efficiency coefficient of 0.90 (0.86) and 0.86 (0.86) for the basin-wide (zone-wise) approach in the Astore and Hunza River Basins, respectively, over the entire simulation period. Mean annual discharge was projected to increase by 11–58% and 14–90% in the Astore and Hunza River Basins, respectively, under all the RCP mid- and late-21st-century scenarios. Mean summer discharge was projected to increase between 10–60% under all the RCP scenarios of mid- and late-21st century in the Astore and Hunza basins. This study suggests that the water resources of Pakistan should be managed properly to lessen the damage to human lives, agriculture, and economy posed by expected future floods as indicated by the climatic projections.
Highlights
The change in climate patterns is one of the major challenges that the world is confronting today, especially due to its diverse and uncertain impacts on water resources
This study suggests that the water resources of Pakistan should be managed properly to lessen the damage to human lives, agriculture, and economy posed by expected future floods as indicated by the climatic projections
An effect of global warming is significantly attributed to the increase in the glacial retreat rate [1,2,3] across the world except for the Karakoram glaciers, which are reported to be advancing [4,5,6,7] in a few regions such as northern areas of Pakistan
Summary
The change in climate patterns is one of the major challenges that the world is confronting today, especially due to its diverse and uncertain impacts on water resources. An effect of global warming is significantly attributed to the increase in the glacial retreat rate [1,2,3] across the world except for the Karakoram glaciers, which are reported to be advancing [4,5,6,7] in a few regions such as northern areas of Pakistan. The impact on access of water resources for irrigation, drinking, hydro-based industries, and hydropower are the major implications arising from changes in peak runoff and water balance [8,9] due to climate change.
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