Evaluating effect of downscaling methods; change-factor and LARS-WG on surface runoff (A case study of Azam-Harat River basin, Iran)

Document Type : Research Paper


1 Department of Watershed Management, Collage of Natural Resources, University of Yazd, Yazd, Iran

2 Department of Irrigation and Drainage Engineering, Collage of Abouraihan, University of Tehran, Pakdasht, Iran

3 Faculty of Natural Resources and Environment, Ferdowsi University Of Mashhad (FUM), Mashhad, Iran


This study aims to evaluate effects of two downscaling methods; change-factor and statistical downscaling on the
runoff of the Azam-Harat River located at Yazd province (with an arid climate) of Iran, under the A2 emission scenario
for the period of 2010-2039. For this purpose, CGCM3-AR4 model; a rainfall-runoff conceptual model, IHACRES; two
downscaling models, Change Factor and LARS-WG were applied. Results show 30% difference in runoff simulated by
two downscaling methods. Also, according to the fact that Change Factor ignores climate fluctuations over the course of
future period relative to base period, simulated runoff from the outputs of this downscaling method does not contain
enough confidence and cannot represent the actual runoff of the basin in the future. Despite, fluctuations are modeled in
the LARS-WG well. On the other hand, if the estimated runoff increase from the LARS-WG is more than the capacity of
the Azam-Harat River and Basin, the risk of flood and damage could figure in the future.