evaluating effect of downscaling methods; change-factor and lars-wg on surface runoff (a case study of azam-harat river basin, iran)

this study aims to evaluate effects of two downscaling methods; change-factor and statistical downscaling on therunoff of the azam-harat river located at yazd province (with an arid climate) of iran, under the a2 emission scenariofor the period of 2010-2039. for this purpose, cgcm3-ar4 model; a rainfall-runoff conceptual model, ihacres; twodownscaling models, change factor and lars-wg were applied. results show 30% difference in runoff simulated bytwo downscaling methods. also, according to the fact that change factor ignores climate fluctuations over the course offuture period relative to base period, simulated runoff from the outputs of this downscaling method does not containenough confidence and cannot represent the actual runoff of the basin in the future. despite, fluctuations are modeled inthe lars-wg well. on the other hand, if the estimated runoff increase from the lars-wg is more than the capacity ofthe azam-harat river and basin, the risk of flood and damage could figure in the future.