Climate Change Impacts on Surface Runoff in the Hyrcanian Forests

The Hyrcanian forests are green belt stretching over the northern slopes of the Alborz mountain ranges and cover the southern coasts of the Caspian Sea. The climate of this region is controlled by several components of a regional atmospheric circulation pattern and is strongly modulated by a complex topography and the maritime effect of the Caspian Sea. Climate change will accelerate the hydrologic cycle, altering rainfall, and the magnitude and timing of runoff. Hyrcanian forests might become one of the most vulnerable areas in the world regarding climate change. Therefore, the purpose of this paper is to assess the impacts of climate change on surface runoff from the Hyrcanian forests in the North of Iran. To study the effects of climatic variations, the SWAT model was implemented to simulate the hydrological regime and the SUFI-2 algorithm was used for parameter optimization. The climate change scenarios were constructed using outcomes of three General Circulation Models (CGCM2, HadCM3, and SCIRO2) for three emission scenarios (A1F1, A2 and B1) by adjusting the baseline climatic variables that represent the current precipitation and temperature patterns. The study results for 2040-2069 compared with the present climate showed changes in surface runoff by -1.3%, 5% and -1.2% for the A1F1, A2 and B1 scenarios, respectively. Monthly variations show pronounced increases in discharge in the wet season (February-May) and decrease in dry season (July-September). The results highlight the strong impact of climate change in surface runoff and reflect the importance of incorporating such analysis into adaptive management