study on effects of climate changes on surface runoff changes case study: urmia lake basin

climate change is one of the most important problems in the present century. so assessing and prediction of future changes is important on water resources and so important for economics and socio-economic consequences. the purpose of this research is assessing the effects of climate change on surface runoff volumes under the scenarios: a1b, a2 and b1 using hadcm3 general circulation model and ihacres rainfall-runoff model for three time periods (2011-2030, 2046-2065 and 2080-2099). lars-wg downscaling model were used to bridge global data to sits, datasets. the results of the evaluation of observed and simulation data using statistical and of measurement error indices show that not difference between the simulated and the observed values on the critical error 0.5% .the results of climate model show that the average temperature of basin will be increased between 0.55 to 3.15 ° c, and rainfall reduces amount 11.94 percent in the basin. performance analysis of ihacres rainfall-runoff model also showed good accuracy of the model to simulate the runoff changes in basin. the results the study of surface runoff changes showed that the long-term average of annual runoff is reduced in 2020s, 2050s and 2080s than the base period, respectively 5.4, 22.35 and 64.5 percent.