ABSTRACT Four panels. Panel 1: Map of Sardabrud Basin, Iran, near Caspian Sea. Panel 2: CMIP6 climate models including precipitation and temperature projection by GFDL-ESM4 under SSP scenarios. Panel 3: SWAT model. Panel 4: Runoff projections under SSP1-2. 6, SSP3-7. 0, SSP5-8. 5. This study examines the impact of climate change on glacial watersheds and downstream rivers in northern Iran using the SWAT model and CMIP6 scenarios. Historical data (1987–2016) on precipitation, temperature, and runoff from the Alam Kuh catchment were analyzed using regression methods. The Mann-Kendall test was used to evaluate the significance of historical trends in precipitation, temperature, and runoff. Among the CMIP6 models tested, GFDLESM4 showed the best performance with the lowest index error. Future changes in temperature and precipitation for the period 2025–2050 were projected using CMHyd downscaling under three climate scenarios: SSP1-2. 6, SSP2-4. 5, and SSP5-8. 5. Results indicate average temperature increases of 1. 2, 1. 0, and 1. 5 °C for the respective scenarios, corresponding to 7, 6, and 10% rises compared to the baseline period (1987–2016). Precipitation is projected to decline by 5, 8, and 10%, respectively. These climatic projections were input into the SWAT model to assess impacts on river flow. The findings show streamflow reductions of 3% under SSP1-2. 6, 6% under SSP2-4. 5, and 13% under SSP5-8. 5. Notably, under the SSP5-8. 5 scenario, river discharge during summer is expected to decrease by as much as 31%, indicating significant seasonal vulnerability in water availability.
Motiee et al. (Fri,) studied this question.