The spatial-temporal changes in water balance components under future climate change in the Gorganroud Watershed, Iran

The quantitative assessment of water balance components is crucial for sustainable management of watersheds. These components have been affected by climate change over the recent years across the world, specifically in semi-arid regions like Iran. This study aims to evaluate the effects of future climate change on the hydrological components in the Gorganroud watershed, northern Iran. In this regard, the Soil and Water Assessment Tool (SWAT) was calibrated and validated to simulate hydrological processes under future climate conditions. We also used the outputs from a Coupled Model Intercomparison Project Phase 9 (CMIP6) climate model to project future climate variables for 2025–2054 and 2071–2100 periods. The Quantile Mapping (QM) method was applied to remove the systematic biases in the simulated climate datasets. Our findings indicate that (1) minimum and maximum temperature will likely rise up to 3.3 °C and 4.3 °C, respectively, during 2071–2100 compared to the baseline of 1985–2014 under SSP585, (2) precipitation is predicted to increase up to 5.6% under SSP245, while it is expected to decrease up to 5% under the SSP585 in 2071-2100compared to the baseline, (3) in response to climate change, the study area will see a reduction in surface runoff, base flow, and lateral flow up to 7.7%, 13% and 10.2%, respectively, and an increase in evapotranspiration up to 11%) until the end of the century, (4) spatial analysis indicates that the eastern, southeastern, and northern regions of the watershed are projected to experience the most significant declines in hydrological components, with changes up to 50%. These results highlight could provide valuable information for decision and policy-makers to adaptively manage and plan strategies in the future for the Gorganroud watershed.