Understanding the impact of climate change on future climate extremes in the Gandak River Basin: A multi-model ensemble-based analysis

The study analyzed the spatio-temporal variability of extreme temperature & precipitation indices in the Gandak River Basin (GRB) under two socio-economic scenarios (SSP245 and SSP585) utilizing CMIP6 multi-model ensemble projection for the Near-Term (2020–2050) & Far-Term (2060–2090). Consecutive Dry Days are likely to decrease slightly in all areas, whereas Consecutive Wet Days indicate uniform increasing percentage of change w.r.t. baseline, particularly in SSP585 scenario. Himalayan ranges, especially the Dhaulagiri and Annapurna, are likely to experience up to 50–90 % increase in CWD in far-term under SSP585. RX1D and RX5D indices indicate decreasing percentage of change w.r.t. the baseline, but with extreme spatial heterogeneity between the higher elevations and lower plains. Trend analysis using Mann-Kendall test and Sen's slope show significant increasing trend in RX1D & RX5D for GRB. Temperature indices exhibit a prominent trend of warming across the basin, with the most pronounced in the Central Himalayas in both the scenarios, with the maximum magnitude observed in the SSP585 Far-Term scenario. The Far-Term under SSP585 shows the most severe warming, with the highest temperature rise at the maximum level of up to 2.41 °C/year and the rise in monthly minimum value of daily maximum temperature up to 1.91 °C/year. These insights have direct implications for the management of water resources and disaster preparedness in the GRB. Extended wet spell conditions may pose an increased flood threat, while increasing warmth may aggravate water scarcity and ecosystem disruptions. This calls for adaptive management strategies to enhance climate resilience in the region.