Impacts of climate Change on Runoff from Snowmelt (Case Study: Shahrchay River Basin Urmia)

According to importance of snowfall in water supply of mountainous area, accurate estimationof water equivalent from snow and monitoring its coverage is so important in agriculture,energy, reservoir management and flood warnings. In this study, runoff originated from snowmelt in Shahrchay river basin under the terms of climate change calculated. For this purpose,snow cover for water year of 2012-2013 were extracted in ENVI software using the dailyimages of Modis satellite with 1km spatial resolution. Then, by using the Hec_GeoHMS in GISsoftware the physiographic characteristics of the basin extracted. In the next step, data of snowcover, meteorological variables and other necessary parameters to SRM model provided as aninput of the model and run-off from snow melt was simulated. In climate phase, first output ofthe six models of atmospheric general circulation with title of 3 scenarios namely A1B, A2 andB1 converted to a downscaling by using LARS-WG model. Then, in order to evaluate theuncertainty of models and scenarios, by comparing the output of the six models in the futuretime period with that of the base time period in monthly time scale some indices namelycoefficient of determination (R2) and Root Mean Square Error (RMSE) applied to select thebest 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 theprecipitation data, whereas, the MPEH5 with the A2 scenario was used to generate the airtemperature data. In order to estimate the rate of change of runoff originated from snowmeltthe rate of change of monthly data of air temperature and precipitation in the base time periodas well as future time period under the selected model and scenario was used as input to SRMmodel in simulation time period. Results showed that the amount of runoff originated fromsnowmelt in late spring will be decreased. The peak flow appeared earlier in time(approximately one month) in comparison with the base period and the peak discharge valuewould be increased comparing the base period.