Quantifying impacts of precipitation and evapotranspiration on future runoff in the Han River basin using the Budyko framework

• The contributions of precipitation and evapotranspiration on future runoff are quantified using the Budyko framework. • The aridity index (PET/P) is projected to decline, indicating a shift toward a more humid climate. • The elasticity coefficients for P and PET are projected to change insignificantly across future periods. • Precipitation contributes the change in runoff, contributing by 67%–84%, while PET contributes by 11%–24%. Changes in hydrometeorological variables due to climate change are expected to affect changes in runoff, posing challenges for water resource management and increasing the risk of economic and environmental hazards. This study simulated future runoff in the Han River basin using the GR4J model under different climate change scenarios. The climate elasticity approach based on the Budyko framework quantified the contributions of precipitation (P) and potential evapotranspiration (PET) to changes in runoff. Runoff was projected to increase for the near future (NF, 2021–2060) and far future (FF, 2061–2100) compared to the baseline period (BP, 1975–2020). Runoff increased by 22.39% for NF and 34.72% for FF under the SSP2-4.5 scenario and by 27.46% for NF and 48.45% for FF under the SSP5-8.5 scenario. The aridity index (PET/P) decreased by 0.08–0.09, indicating a shift toward a more humid climate. Because PET contributed 11%–24% and P contributed 67%–84%, P was identified as the main cause of the change in runoff. The findings of this study can be beneficial for water resource management and establishing climate change adaptation for the Han River basin.