Hydroclimatological Response of Selected Subbasins of the Upper Indus Basin for Mid and End Century Climate Change

Abstract

Variability in the radiative balance of the earth resulting in climate change has posed immense challenges, such as rising temperatures, altered precipitation patterns and increased frequency of extreme weather events. These have jeopardized the availability of water, food and health conditions for the humans. Pakistan’s geographical location makes it one of the most affected countries by climate change. Hence the study was conducted to investigate the climate variability and the impact of projected climate change on the future streamflow of the Hunza, Astore and Shigar River basin located in the Hindukush Karakorum Himalaya (HKH) region. To examine the climate variability annual and seasonal (winter & spring, pre-monsoon and monsoon).trend and correlation analysis of the temperature and precipitation records, river discharge and basin-wide (BW) and altitudinal zonewise (z1, z2 & z3) snow cover area (SCA) was carried out covering a period from 2000 to 2018 . The Modified Mann Kendall (MKK) test was utilized to analyze the trends. The Kendall Rank, Spearman and Pearson correlation tests were employed to conduct correlation analysis. The snow images were obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). Four CMIP6 based GCMs, including MPI-ESM1-2-HR, MIROC6, NEMS3 and INM-CM3 under Shared Socioeconomic Pathway (SSP245 and SSP585) were utilized to investigate the future changes in annual and seasonal temperature and precipitation across the Early century (2025-2050), Midcentury (2050-2075), and Late century (2075-2100)) in the study area. Moreover, the hydrological model Snowmelt Runoff Model (SRM) was applied over the study basins to investigate future changes in hydrological components over the study basins till the end of 21st century. The MODIS investigation suggested an overall BW and ZW decline in SCA in the three basins. Moreover, the temperature trend analysis suggested an increase in annual and seasonal BW temperature indicating warming in the three basins. Further, the CMIP6 based simulations exhibited an increase in mean annual temperature under SSP245 and SSP585, throughout the 21st century. Based on average temperature change for all scenario periods the monsoon, pre-monsoon, and winter & spring are categorized as first, second and third respectively, for the rise in annual precipitation under SSP585 for 21st end century. Significant heterogeneity in projected precipitation has been observed in the three basins and even at different stations within the same basin. The Astore, Hunza and Shigar basins are classified as first, second and third, respectively, for the rise in annual precipitation under SSP585 for 21st end century. The SRM generated future streamflow projections presented a substantial shift in hydrological response of the study basins. For all the scenario periods an increase in average annual streamflow in the basins has been observed. This is in response to the rise in temperature that is instigating a significant rise in snow and glacier-melt runoff. The stream flow projections for the pre-monsoon season indicated an earlier offset and considerable surge in the three basins in coming decades for all the scenarios, especially for the end-century simulations. Hence the study results reveal that climate change will significantly affect the hydroclimatology of the study basins. This could severely impact water availability across the Indus River Basin, both upstream and downstream areas. The objective of the research conducted was to interpret the consequences of climate change on SCA and water resources hence the research results are highly beneficial for effective sustainable water resource management and flood risk assessment in the study area. The study undertaken closely aligns with several United Nations Sustainable Development Goals (UNSDGs), particularly SDG 13 (Climate Action) and SDG 6 (Clean Water and Sanitation).