Assessing the impact of climate change on streamflow in the Tamor River Basin, Nepal: an analysis using SWAT and CMIP6 scenarios

Understanding and anticipating the impacts of climate change on hydrological processes is crucial for sustainable water resource management. This study investigates the projected alterations in streamflow within the Tamor River Basin, Nepal, under changing climatic conditions, utilizing the soil and water assessment tool (SWAT). Future climatic variables, including precipitation, maximum, and minimum temperature, were assessed for the near (2022–2047), mid (2048–2073), and far future (2074–2100) periods under two shared socioeconomic pathways (SSPs): SSP245 and SSP585. Bias-corrected outputs from coupled model intercomparison project, phase 6 (CMIP6) models were integrated into the SWAT model to simulate the basin's hydrological response. Results indicate that, under the SSP245 scenario, annual average maximum and minimum temperatures are expected to rise by ~ 0.046 °C and 0.050 °C, respectively, with a 12.70% increase in precipitation. Similarly, the SSP585 scenario predicts temperature increases of 0.063 °C and 0.085 °C, alongside an 11.90% rise in precipitation. These climatic changes are projected to result in a significant increase in streamflow, with an estimated rise up to 20% by the end of the twenty-first century. The findings of this research provide valuable insights for policymakers and stakeholders, facilitating informed decision-making for the sustainable management of water resources in the face of climate change.