Given Iran's acute decline in water resources, investigating the impacts of climate change on hydrological cycles and water scarcity dynamics is critical for adaptive management. This study evaluates future hydrological changes in Iran under climate scenarios to inform sustainable water resource planning.
Historical monthly precipitation, temperature, and river flow data (1976–2005) were obtained from Iran’s Meteorological Organization and Ministry of Energy. Future climate projections (2021–2050) were derived using the CSIRO-Mk3-6-0 model from the CMIP5 ensemble under four RCP scenarios (2.6, 4.5, 6.0, 8.5). A statistical change factor method was applied for downscaling.
Results indicate consistent precipitation declines across all scenarios, particularly in December (8–13 mm), January (16–32 mm), March (18–20 mm), April (7–22 mm), and October (5–8 mm). Seasonal reductions are pronounced in fall (7–22%) and winter (8–32%), with the maximum annual decrease (14.5%) under RCP4.5. Concurrently, temperatures are projected to rise by 0.4–2.7°C, exacerbating hydrological stress. Runoff in the Dez River Basin is expected to decline by 4.0–7.2%, peaking at 7.2% under RCP4.5 by mid-century (2041–2050). These findings underscore the urgency of adaptive strategies to mitigate climate-driven water shortages. The integration of observational data and hydrological modeling (e.g., IHACRES) provides a robust framework for assessing future scenarios, offering critical insights for policymakers in arid regions facing similar challenges.