Scenarios In Climate Change Impact Assessment on Monthly Stream-flow of Karun Basin

In this paper uncertainties of GCM’s structure and emission scenarios in climate change impact assessment on monthly stream-flow of Bashar River basins are investigated and compared.
stream-flow of the basin was simulated using a conceptual rainfall-runoff model. Climate scenarios simulated by 6 GCM under 3 emission scenarios for 2063-93 periods were downscaled using change factors method. Using these 18 future scenarios and observed climate data as inputs of the rainfall-runoff model, climate change impact on monthly stream-flow of the basin was assessed. Ranges of the results under various GCMs and emission scenarios were assessed and uncertainty of the GCMs and emission scenarios in the results were investigated.
In simulation of the monthly stream-flow of the basin, coefficient of determination (R2) reached values of 0.96 and 0.94 during calibration and validation, respectively. Under each of emission scenarios and GCMs it is projected that the amounts and annual cycle of the stream-flow will change. However, the amount and direction of the changes are different for various GCMs and emission scenarios. As instant, for September’s under various GCMs and emission scenarios the mean stream-flow may changes between 26% decrease to 123% increase.
It is projected that climate change will have important impacts on the basin’s stream-flow. The uncertainty from GCM structure is larger than uncertainty from emission scenarios. However, the uncertainty from emission scenarios is significant, too, and cannot be ignored.