Forecasting near-future impacts of land use and climate change on the Zilbier river hydrological regime, northwestern Iran

We study and forecast the effects of near-future (NF) land use and climate changes (LUCC) on the hydrological regime (HR) within the Zilbier river basin located in arid and semiarid regions, in the Azerbaijan province in northeast and northwest of Iran in the recent past (2004-2014) and 2030. We used the baseline data (S-B) and 13 potential NF scenarios to evaluate the effects of changes in land use, temperature and precipitation, both in isolation and in combined scenarios by application of the Soil and Water Assessment Tool (SWAT). Climate changes (CC) were represented by the delta change approach based on trends for past 3 (1985-2014) or last decade (2005-2014), respectively (low delta change (LDC) and high delta change (HDC)), where the trends of the most recent decade yield a higher delta change when extrapolating to 2030. Similarly, land use changes were derived from trends observed based from satellite imagery and Cellular Automata-Markov model (CAM). In the NF, the results indicated that the climate would universally become warmer and drier under both LDC and HDC and increase the high-consumption land uses such as orchards in the study area, respectively. In 2030, CC tend to effect more conspicuously the HR than LU changes, leading to decrease in the entire hydrological component except evapotranspiration. Surveying the whole array of the simulated scenarios, there were clear and non-linear synergistic effects of the combination of LU and CC scenarios, and taking into account both of these is, therefore, critically important if model results are to be used for decision-making support.