Changes in the spatial variability of extreme climate characteristics across the Sabarmati River basin: Past and future

Climate change significantly impacts the global and regional hydrological dynamics, consequently altering the climate extremes. Through a comprehensive analysis, this study presents how the spatial variability of climate extremes is changing in major west-flowing Sabarmati River basin (SRB) in India, due to a gradually warming climate. A methodological framework to assess joint variability and temporal evolution of climate extremes for a semi-arid, water-scarce, and densely populated region, using baseline and future datasets is developed. Here, the statistically downscaled climate projections of five general circulation models (GCMs) of the coupled model intercomparison project (CMIP5) under two representative concentration pathway (RCP) scenarios are analyzed for the SRB. The study performs robust statistical analyses to assess the projected (2020-2100) changes with reference to the baseline (1951-2019) period using a multi-model mean ensemble approach. The distributional changes in climate extremes are evaluated using non-parametric kernel density estimates and the Mann-Whitney test. The individual and joint variability of rainfall and temperature indices is investigated using correlation and principal component analysis. The results show that the SRB will experience a wetter and warmer climate in the future, with increased frequency and intensity of extreme events such as heat waves, flash floods, and droughts. Further, the heat waves may likely intensify, while the cold waves would subside by the end of 21st century. A strong dependency between the rainfall and temperature extremes is detected in the SRB under higher levels of anthropogenic warming (i.e., RCP8.5) compared to the RCP4.5 and baseline period, indicating a sign of global warming in the far future. The results urge the need for immediate and effective policy actions to reduce climate change impacts for sustainable development in the basin.