Assessing Independent and Combined Effects of Land Use and Climate Change on Basin Runoff: A Remote Sensing, Statistical and Hydrological Modeling Approach

The key focus of this study is the use of future climate and land use data obtained from appropriate projection models to assess long-term annual streamflow changes in a basin located in northern Iran. Future climate projections were derived from the CanESM2 model under two Representative Concentration Pathways (RCP2.6 and RCP8.5), using the SDSM downscaling model for the mid- and end-21st century. The future land use map for the year 2050 was obtained from the Land Use Modeler (LCM). Streamflow under projected land use change (LUC) and climate change (CC) scenarios was simulated using the Soil and Water Assessment Tool (SWAT). The climate change evaluation indicates that precipitation will increase (up to 24%) in winter but decrease (up to -37%) in spring, summer, and autumn (except December). Additionally, temperature will rise in all months of the year. The effects of climate change on the Nekarood Basin are expected to increase streamflow in winter and decrease it in spring (except April), summer, and autumn (except December). The streamflow simulation results under the influence of land use change show that peak flow values will increase, while base flow will decrease. The combined effects of LUC and CC are projected to intensify future streamflow responses, with decreases of -2.9%, -8.3%, -8.1%, and − 9.2% in mid-century/RCP2.6, mid-century/RCP8.5, end-century/RCP2.6, and end-century/RCP8.5, respectively. A specific finding of this study is that the annual variations in streamflow are strongly influenced by climate in the basin.