Comparison of SVM, GEP and IHACRES Models in Prediction of Runoff Changes Due to Climate Change (Case Study: Jamishan Dam)

Today, the effects of climate change and global warming have been demonstrated by rising greenhouse gases. Occurrence of these conditions affects hydrological processes such as precipitation and river flow, which is one of the main sources of water for the basin. In this study, the monthly values of precipitation, temperature and inflow of Jamishan Dam during the period of 1988-2017 are considered as the basic period. The output of climate models does not have the desired accuracy and spatial and temporal resolution, so it is necessary to downscale the output of CMIP5 models for the study area. In this study, using Change Factor Method (CFM), the data of two FLO_ESM and CNRM_CM5 models were downscaled under the RCP8.5 scenario and the monthly temperature and precipitation parameters of Jamshan dam were produced for the period 2021-2050. To evaluate the effect of climate change on runoff in the region, SVM, GEP and IHACRES models were studied and compared. The results of climate model indicate an increase in temperature between 0.1 to 1.4 degrees of Celsius for both FLO_ESM and CNRM_CM5 models. Also, the results of simulated precipitation in FLO_ESM and CNRM_CM5 models show that the monthly long-term average under the RCP8.5 scenario in the next period decreased 1.1 and 5.8%, respectively, as compared to the baseline period. In general, the results show a reduction in runoff in all three models (SVM, GEP and IHACRES), which the highest reduction (28.9%) is corresponded to SVM in FLO_ESM model and the lowest reduction (14.1%) is corresponded to GEP in CNRM_CM5 model. In this study, GEP and IHACRES models are more accurate than the SVM model.