Impact of Climate Change on Runoff from Snowmelt by Taking into Account the Uncertainty of GCM Models (Case Study: Shahrchay Basin in Urmia)

Abstract

According to importance of snowfall in water supply, in this study, runoff originated from snow melt in Shahrchay river basin under the terms of climate change calculated. For this purpose, for water year of 2012-2013, by using the SRM model, run-off from snow melt was simulated. In climate phase, first output of the six models of atmospheric general circulation converted to a downscaling by using LARS-WG model. Then, in order to evaluate the uncertainty, by comparing the output of the six models in the future time period with that of the base time period in monthly time scale some indices namely R² and RMSE applied to select the best model and scenario of air temperature and precipitation data generator of the period 2011-2030. Therefore, the HADCM3 model with the scenario A₁B was used to generate the precipitation data, whereas, the MPEH5 with the A₂ scenario was used to generate the air temperature data. In order to estimate the rate of change of runoff originated from snowmelt the rate of change of monthly data of air temperature and precipitation in the base time period as well as future time period under the selected model and scenario was used as input to SRM model in simulation time period. Results showed that the amount of runoff originated from snowmelt in late spring will be decreased. The peak flow appeared earlier in time in comparison with the base period and the peak discharge value would be increased comparing the base period.