Investigation of the effect of climate change under emission scenarios on intensity-duration-frequency curves of precipitation in Zahedan Synoptic Station using Fractal theory

Rainfall intensity-duration-frequency (IDF) curves are used to plan, design and operate water resources projects or to protect various engineering projects against floods. Curves created from past climates cannot be valid for the future climates unless they are updated with future climatic trends. The purpose of this study is to investigate the effect of climate change on IDF curves in Zahedan Synoptic Station. First, the fractal behavior of precipitation at the station was investigated and the results showed that the maximum intensity of precipitation follows the monofractal behavior. Theoretical error was calculated by the method of relative difference (RD) and the results showed that the errors are within the allowable range, then the curves are extracted for the base period (1982 to 2019) and for the return period of 2, 5, 10, 50, 100 and 200 years. Further, future precipitation data (2021 to 2055) were predicted using HadGEM2-ES general circulation model, from the CMIP5 series of models, under the RCP4.5 and RCP8.5 emission scenarios, and using LARS-WG statistical downscaling model. Based on future data, IDF curves for the future were extracted employing the fractal theory. Comparison of base and future period curves showed that the average maximum rainfall intensity in different durations and return periods increased by 22.9% under RCP4.5 scenario and decreased by 11.1% under RCP8.5 scenario.