Temporary and spatial analysis of drought in Çekerek River Basin with real-time and remote sensing data

Climate change is one of the most environmentally critical problems of the present day. Climate change creates many environmental and social problems due to population growth, industrialization, deforestation, and the reckless consumption of resources. In this context, drought is among the most critical issues affecting ecology, environment, meteorology, hydrology, and agriculture. Studies on drought in the literature highlight the importance of continuous drought monitoring studies based on natural indicators in determining drought severity, spatial extent, and impacts. In this study, the drought status in the Çekerek Basin was evaluated with different drought indices using meteorological and remote sensing data. In the first stage, the agricultural drought status of the selected stations was assessed with the Palmer Drought Severity Index (PDSI), which is calculated using meteorological and ground-based data. For this purpose, five PDSI calculations were made using terrestrial data obtained from non-irrigated wheat fields: Conventional PDSI, PDSI(30), PDSI(B.CROP), Real-Time PDSI (Real-Time PDSI), and Satellite-Based PDSI. The relationship between these PDSI approaches was evaluated using correlation analysis. In the second stage, the meteorological drought status of the basin was analyzed using the Standardized Precipitation Evapotranspiration Index (SPEI). The temporal change of the SPEI index was evaluated using Innovative Trend Analysis (ITA), and its spatial change was assessed using the Inverse Distance Weighted (IDW) interpolation method. In the final stage, the relationship between SPEI and the Plant Health Index (VHI) was examined using correlation analysis to determine the impact of meteorological drought (SPEI) on agricultural drought. According to the analysis results, a strong correlation was found between the Traditional PDSI and PDSI(30) approaches; similarly, the PDSI(B.CROP) approach showed high consistency with these indices. While the Satellite-Based PDSI showed some correlation with the other methods, the strength of this relationship was observed to be relatively weak. It was also determined that Real-Time PDSI values, calculated through monthly soil moisture monitoring, did not align with those obtained from the other methods. Findings regarding the temporal and spatial distribution of meteorological drought revealed no significant change in drought trend throughout the basin except for Sulusaray station, but the spatial distribution of drought varied over the years. Furthermore, when the impact of meteorological drought on agricultural drought was examined, a significant relationship between SPEI and VHI was observed only during certain months, indicating a generally weak correlation between these two indices. According to the findings, it was concluded that agricultural drought should be evaluated at the plant level and over smaller areas (e.g., plot or field scale), rather than across large basins. Moreover, it was determined that meteorological data alone are insufficient for drought assessment and should be supported by ground-based and satellite data.