Climate change impact assessment on hydrological regimes of a mountainous river basin in Iran

In this paper climate change impacts on hydrological regime of a mountainous river basin is assessed. In order to do that, scenarios of global climate models are downscaled by using change factor method. The climate scenarios are used as inputs of a rainfall-runoff model, which is well calibrated for the basin, and daily stream-flow series for present condition and future scenarios (2067-93) are simulated. By comparison of river-flow characteristics for present condition and future scenarios, the climate change impacts on hydrologic regime of the basin are assessed. for analysis of the emission scenarios uncertainty, scenarios of A2, A1B, and B1, which relevant to high, medium, and low emission scenarios, respectively. Based on the results, basin temperature will increase between 3 to 5 Celsius degrees and potential evapotranspiration will increase for all month of the year. Despite uncertainty of emission scenarios, under all emission scenarios, annual average of rainfall and stream flow will raise; however, seasonal cycle of rainfall and river flow will change, too. Average river flow in the autumn and winter will increase, while the average river flow in spring and summer will decrease. Decreasing of the river flow in the second half of the water year, Implies the importance of considering of the climate change impacts on the river-flow for designing of dam’s reservoir.