Trend analysis and change point determination for hydro-meteorological and groundwater data of Kizilirmak basin

Climate change–induced changes in hydro-meteorological parameters such as precipitation, temperature, and evaporation have also altered water cycle components in various parts of the world. Severity of droughts then gradually increases with these changes. In this article, the precipitation, temperature, streamflow, and groundwater data of the stations in the Kizilirmak basin between 1970 and 2017 were studied. Precipitation (P), maximum temperature (Tmax), minimum temperature (Tmin), and mean temperature (Tmean) data that were taken from 20 meteorology stations were used. For trend analysis, linear regression (LR) and non-parametric Mann–Kendall (MK), modified Mann–Kendall (Hamed‒MK), and Spearman’s Rho (SRHO) methods were used to find out the trends in time series. Pettit test was used to determine the inception period of the trend. Although increasing trends were observed in maximum and minimum temperatures across the basin, significant trends were not observed in mean temperatures. All significant precipitation trends were in increasing direction, except for the Ilgaz station. In the change point analysis, the directional change that is occurring in maximum and minimum temperatures corresponded to the period between 1993 and 1998. On the other hand, such a period coincided to the period between 1983 and 1997. Generally decreasing trends were observed in flows, except for three stations. Majority of the present stations had increasing trends in groundwater levels. Increasing trends, on the other hand, are thought to occur due to the increase in groundwater consumptions.