Comprehensive Analysis of the Impact of Land Use Dynamics and Climate Change Scenarios on Hydrological Processes

Effective management of water resources under changing environmental, socio-economic, and extreme climate conditions requires a clear understanding of hydrological components and sediment yield. This study presents a comprehensive integration of highresolution land use dynamics and CMIP6 climate projections to assess their combined impacts on all hydrological processes and sediment yield in Iran’s Gharesou watershed across seven scenarios. Among five climatic models, the GFDL-ESM4 was used to project future climate under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5) for the periods 2011 ~ 2040, 2041 ~ 2070, and 2071 ~ 2100, predicting significant increases in precipitation and temperature (up to +4.15 °C). High-resolution land use maps generated from 1991 to 2081 revealed substantial shifts, including a decrease in forests (–13.4%) and rangelands (~ 44.9%) and an increase in built-up (+39.1%) and cultivated (+10.7%) areas. The scenario combining SSP2-4.5 for the 2071 ~ 2100 period with 2081 land use data, highlighted the most pronounced hydrological changes, with a 20.58% increase in mean annual surface runoff and a 193.96% surge in sediment yield. Concurrently, evapotranspiration and lateral flow decreased by 4.98% and 16.54%, respectively. These changes were primarily driven by land use alterations, demonstrating a stronger correlation with hydrological impacts (correlation of 0.91) compared to climate factors. These insights are crucial for informing effective water resources management, and soil and water conservation strategies, in the Gharesou watershed and similar areas.