Projected changes in hydro-climatic extremes with CMIP6 climate model outputs: a case of rain-fed river systems in Western Nepal

Climate change has increased the intensity and frequency of hydro-climatic extremes in many parts of the world and they are projected to continue in the future too, thus, posing a major threat to agriculture, biodiversity, ecosystems, and water systems. This study characterized the historical as well as projected future hydro-climatic extremes in the eleven rain-fed watersheds in western Nepal (i.e., south-western watersheds, SWWs). Sixteen climate extreme indices were analyzed using ClimPACT2 tool and nine hydrological extremes using IHA tool. Five CMIP6-based climate models driven by SSP245 and SSP585 scenarios were used to project the future climate. Results showed that the SWWs have experienced progressive warming and increased rainfall during the historical period (1980-2014), and this rising trend is projected to be more prominent in the future (2021-2100), posing risks to the socio-environmental equilibrium. Establishing a positive correlation between the occurrences of climatic and hydrologic extremes, this study also points towards more prevalence of hydrological extremes in the future as well, and therefore, suggests policy and technology recommendations to reduce and adapt to climate change, intending to alert relevant authorities to promptly enact climate-related policies.