development of intensity-duration-frequency curves at basin scale using the era5 reanalysis product

Intensity-duration-frequency (idf) curves are essential for hydrological modeling, infrastructure design, and flood risk management. however, traditional methods of idf curve development relying on ground-based observations face significant limitations, including sparse spatial coverage, short temporal records, and the stationary assumption, particularly in the context of climate change. accordingly, this study addresses these challenges by utilizing era5 reanalysis data to develop basin-scale idf curves for the karkheh river basin (krb) in iran. the annual maximum precipitation (amp) series for durations of 6-, 12-, 18-, and 24-hours were extracted from era5 data and corrected for bias using observed precipitation from seven synoptic stations. the bias correction significantly improved era5 estimates, especially in high-altitude regions. a relationship between elevation and bias factors was established to extend the correction across the basin. the corrected amp data were then modeled using the generalized extreme value (gev) distribution, considering both stationary and non-stationary conditions, to construct spatially distributed idf curves based on 82 grid points across the basin. the spatial maps of idf indicate that rainfall intensity varies significantly across the basin, with higher intensities observed in elevated regions. these maps provide detailed and reliable rainfall intensity estimates compared to traditional station-based methods. this work highlights the potential of era5 data, combined with robust bias correction, to enhance hydrological analysis in data-scarce regions.