Trend analysis of potential evapotranspiration data of some stations in the Kızılırmak basin

Determining the trend in potential evapotranspiration (PET) values is of great importance in climate change, drought and management of agricultural water resources. The possible effects of climate change, especially on hydrological processes, are explained only by changes in precipitation and temperature but this is insufficient. In this study, trend analyses of seasonal and annual PET values calculated between 1960-2022 for meteorological stations in the Kızılırmak basin (Çankırı, Kastamonu, Kayseri, Kırıkkale, Kırşehir, Nevşehir, Niğde, Sivas, Yozgat) were evaluated. Seasonal and annual PET values were calculated with the R Studio program 'trendchange' database. According to the Run (Swed-Eisenhart) homogeneity test in the average temperature data of the stations, all stations except Kastamonu and Niğde stations were found to be homogeneous. PET values were calculated using the Thornthwaite method, it was concluded that Kayseri, Kırıkkale, and Niğde stations were not homogeneous and the other stations were homogeneous. According to Şen's Innovative Trend Analysis Method (ITA), except for the decreasing significant trend in winter PET values at Kırşehir station with a confidence interval of 99% (-0.015), an increasing considerable trend was found in all stations in all seasons and annual PET values with a confidence interval of 99% (0.021-0.120). The results show that despite the decrease in precipitation in recent years, the increase in potential evapotranspiration values due to increasing temperatures may effectively increase drought severity.