Climatic and hydrological projections to changing climate under CORDEX-South Asia experiments over the Karakoram-Hindukush-Himalayan water towers

Muhammad Azmat; Aasia Wahab; Christian Huggel; Muhammad Uzair Qamar; Ejaz Hussain; Shakil Ahmad; Abdul Waheed

doi:10.1016/j.scitotenv.2019.135010

Climatic and hydrological projections to changing climate under CORDEX-South Asia experiments over the Karakoram-Hindukush-Himalayan water towers

Sci Total Environ. 2020 Feb 10:703:135010. doi: 10.1016/j.scitotenv.2019.135010. Epub 2019 Nov 3.

Authors

Muhammad Azmat¹, Aasia Wahab², Christian Huggel³, Muhammad Uzair Qamar⁴, Ejaz Hussain⁵, Shakil Ahmad⁶, Abdul Waheed⁷

Affiliations

¹ School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Islamabad, Pakistan. Electronic address: azmat@igis.nust.edu.pk.
² School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Islamabad, Pakistan. Electronic address: awahab.ms15igis@igis.nust.edu.pk.
³ Department of Geography, University of Zurich, Switzerland. Electronic address: christian.huggel@geo.uzh.ch.
⁴ Department of Irrigation and Drainage, Faculty of Agricultural Engineering and Technology, University of Agriculture, Faisalabad, Pakistan. Electronic address: muhammad.uzair@uaf.edu.pk.
⁵ School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Islamabad, Pakistan. Electronic address: ejaz@igis.nust.edu.pk.
⁶ School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Islamabad, Pakistan. Electronic address: shakilahmad@nice.nust.edu.pk.
⁷ School of Civil and Environmental Engineering (SCEE), National University of Sciences and Technology (NUST), Islamabad, Pakistan. Electronic address: drwaheed@nit.nust.edu.pk.

PMID: 31757548
DOI: 10.1016/j.scitotenv.2019.135010

Abstract

The complex snow and glacier (cryosphere) dynamics over the "third pole" mountainous regions of the Karakoram-Hindukush-Himalayas (HKH) makes this region challenging for accurate hydrological predictions. The objective of this study is to investigate the impacts of climate change on major hydrological components (precipitation-runoff, snow- and glacier-runoff, evapotranspiration and inter-annual change in streamflows) over the Hunza-, Gilgit- and Astore-River basins, located in HKH. For this purpose, three different hydrological models (snowmelt runoff (SRM), HEC-HMS and HBV are tested over snow- and glacier-covered river basins. These are subsequently integrated with the climate projections simulated from regional climate models (RCMs) developed under CORDEX-SA experiments. The basin-wide RCM-simulations for future scenarios exhibited an increase in precipitation but decline in intensity of rise over high-altitude zones. The temperature rise showed a maximum increase during monsoon by 4.18 °C, 4.37 °C and 4.34 °C over Hunza-, Gilgit- and Astore-River basins, respectively, for the period 2071-2099 (2090s) and a high emission scenario (RCP8.5). Further, in response to rise in precipitation and temperature, the SRM simulations showed a significant increase in snow- glacier-melt runoff (49%, 42% and 46% for SRM) and precipitation runoff (23.8%, 15.7% and 27% for HEC-HMS) in the Hunza-, Gilgit- and Astore-River basins, respectively, for the 2090s under RCP8.5. The streamflow projections for SRM showed a shift in hydrological regime with an increase by 369 (168.4%), 216.5 (74.8%) and 131.8 m³/s (82%) during pre-monsoon in the Hunza-, Gilgit- and Astore-River basins, respectively and then decline by -73.2 m³/s (-13.9%) and -45.4 m³/s (23.4%) during monsoon of the 2090s, in the Hunza- and Astore-River basins, respectively, under RCP8.5. Overall, the projections show that the pre-monsoon and monsoon seasons are expected to be strongly influenced by climate change, through alterations in snow- and glacier-accumulation, and melt regimes with substantial consequences for river runoff in the region.

Keywords: CORDEX regional climate models; Climate change; Climate projection; Hydrological modelling; Snow and glacier modelling.