Simulation of Climate Change Impact on Snowmelt Runoff (case study: Sarab Seyed Ali Watershed - Lorestan)

Snow and snow melt runoff have a major role to play in supplying water. In this study the impact of climate change on runoff caused by snowmelt was studied in Sarab Seyed Ali watershed in north of Lorestan province. In this study, using snow cover level extracted from Landsat 5 and 7 satellite images and climatic data predicted by general circulation model using Lars-WG software snowmelt runoff under three scenarios A1B, A2 and B2 in the year 2010 to 2013 was simulated using the SRM model. The simulation results were evaluated using two statistic including coefficient of determination and volume difference. The value of 0.87 for the coefficient of explanation and -3.62 for the volume difference indicates the accuracy of the model. Then, using these three scenarios, the climate parameters for 2020 to 2060 were predicted through general circulation model, then using the predicted climate parameters, the rate of snow cover was estimated through multivariate regression equations and was into to SRM model. the simulation was done for 2020 to 2060. The results showed that the average runoff in November to May for the three scenarios was 4.3, 4.4 and 4.2 m3/s respectively, while the long-time mean runoff from 1980 to 2013 was 6.07 m3. However, this decrease in future runoff volume can be justified by the reduction of snow cover.