Abstract

In this study, the predicted monthly temperature and rainfall data from HadCM3 model (base period, ۱۹۷۲-۲۰۰۱) and next period (۲۰۱۱-۲۰۴۰) under A2emission scenario were used to investigate the impacts of climate change on runoff variations in the Kor river basin. HadCM3 model output was downscaled based on a temporal downscaling approach (Change Factor) and spatial downscaling approach (Proportional) for the basin. The time series of monthly temperature and precipitation were produced in future period. The results showed that temperature and rainfall will increase and decrease in the future period relative to the base period, respectively. Then, the calibrated IHACRES model was used to model rainfall-runoff relationships in the Kor river basin. Then, the downscaled monthly temperature and rainfall time series in next period were employed to rainfall-runoff model and the monthly runoff time series were simulated for period ۲۰۱۱- ۲۰۴۰. The comparison of future period runoff relative to observed period showed that the annual runoff in the basin for period ۲۰۱۱-۲۰۴۰ will decrease about ۹٫۴۳% with respect to base period.

In this research, impacts of climate change on the streamflow hydrological status of the Arazkooseh River are discussed. After Calibration and validation of the LARS-WG, HadCM3 was downscaled under A2 Scenario in three climatology station. Beside, calibration and validation of the SWAT model were done by observed data relative to past period of times. Streamflow values are then predicted using climatic parameters of period of 2011-2030, 2046-2065 and 2080-2099 years via SWAT model. The results indicated that the average annual temperature will increased around 0.8, 1.2 and 4.9 °C in desired periods, respectively. Precipitation values will increased 8.8 and 11.2 percent in the early and mid- century and it will decreased with 7.8 percent in the last years of century, correspondingly. The peak of rainfall will moved from month of March to the December. Because of climate changes, streamflow will increase 13 and 5 percent in the near periods. By contrast, in this case, it will reduce around 18 percent in far future. In this case research, the river discharge will increased in autumn and will decreased in spring seasons. Likewise, results of estimation showed that the annual peak flow will shifted from month of March to the April.