Assessment of impacts of change in land use and climatic variables on runoff in Tajan River Basin

The main objective of the present study was to investigate runoff response to climate variables as well as landuse change over the past 30 years in Tajan River Basin, using the SWAT model. After the model calibration, four different scenarios were simulated and compared. Comparison of simulated runoff results determined from different scenarios indicated that climatic variables reduced the amount of runoff while the landuse change increased this amount in most months of the year. Simulated runoff under three landuse scenarios in all months demonstrated that the runoff achieved from scenario 1 was smaller than scenarios 2 and 4. In scenario 4, the runoff amount increased by 3–21% and 0.8–13% in Kordkheil station compared to those of scenario 1 and scenario 2, respectively. Furthermore, the increase in runoff for scenario 4 is 3–19% and 2–12% in Rig Cheshmeh station relative to those of scenario 1 and scenario 2, respectively. Nonetheless, the maximum change in runoff was only 6% under climatic variables. Hence, landuse had more significant impacts on the runoff compared to climatic variables.