Impact of climate change on meteorological and hydrological droughts for Upper Coruh Basin, Turkey

Drought is a multifaceted natural hazard that occurs in almost every component of the hydrological cycle. This study investigated future hydro-meteorological droughts using climate projections from an ensemble of 13 European Coordinated Regional Downscaling Experiments (CORDEX) domain outputs under two alternative scenarios of representative concentration pathways (RCP 4.5 and RCP 8.5) for the 2030-2059 and 2070-2099 periods across Upper Coruh Basin, Turkey. The bias-corrected CORDEX climate projections were incorporated into the Soil and Water Assessment Tool (SWAT) hydrological model. In this study, two optimisation algorithms (the sequential uncertainty fitting algorithm of SWAT calibration and uncertainty and the shuffled complex evolution (SCE) algorithm in parameter estimation tool (PEST)) were tested for the automatic parameter calibration of a complex hydrologic model, SWAT, in the study area. Results show that SCE reached better parameter solutions than the other algorithm. This study investigated for the first time a comprehensive analysis of the projected droughts in the Upper Coruh Basin, Turkey. The standardised precipitation index and standardised streamflow index were used to evaluate the meteorological and hydrological droughts, respectively. Overall, the future annual precipitation and the maximum and minimum temperatures are projected to change from - 15.46% to 8.74%, 0.02 degrees C to 8.74 degrees C and - 2.69 degrees C to 5.27 degrees C, respectively. The results show that the frequency of hydrological drought durations will be higher under RCP4.5 and RCP8.5 during the period 2030-2059. In addition, the frequency of hydrological high-severity droughts (> similar to 5) and low-severity droughts (< similar to 2) will be more likely under RCP4.5 and RCP8.5 during the period 2030-2059 and 2070-2099, respectively. Other than this, not enough evidence exists to claim that hydrological and meteorological drought will become more significant in the twenty-first century.