A Comprehensive Assessment of Drought Dynamics in Türkiye: An Integrated Spatiotemporal Analysis of Trends, Variability and Persistence

ABSTRACT

This study provides a comprehensive assessment of meteorological, agro‐ecological, and hydrological drought dynamics in Türkiye over 1980–2022 using the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) at 3‐, 6‐, and 12‐month timescales. Trend magnitudes were quantified using Sen's slope estimator, and trend significance was evaluated using the Hamed‐Rao variance‐corrected Mann‐Kendall (M‐K) test. Temporal evolution was assessed using the sequential Mann‐Kendall (SM‐K) test and a 9‐point low‐pass Gaussian filter highlighting long‐period fluctuations. The Pettitt, Buishand, and Standard Normal Homogeneity Test (SNHT) tests were applied as change point tests, and persistence was evaluated using first‐order detrended fluctuation analysis (DFA). Results revealed a systematic divergence between SPI and SPEI series. While the SPI time series showed no statistically significant trends across annual, water‐year, or seasonal aggregations at the 3‐, 6‐, and 12‐month timescales, the SPEI time series showed statistically significant increasing drought trends across most annual, water‐year, and seasonal series. This indicates that precipitation‐only drought assessment may be incomplete in the case of Türkiye, where rising air temperatures amplify atmospheric evaporative demand and intensify drought‐prone climatic water‐balance conditions. Seasonal analysis indicated that significant SPEI trends concentrated in summer and autumn at the 3‐month scale expanded to include winter at the 6‐month scale and extended to all seasons at the 12‐month scale. SM‐K and Gaussian‐filter results indicated prolonged periods of statistically significant increasing drought trends mainly from the late 1990s and early 2000s onward, while the Pettitt, Buishand, and SNHT tests identified the change point in the SPEI series around 1998–1999. DFA scaling exponent ( α ) values approached or exceeded 1.0, especially for SPEI‐6 and SPEI‐12, indicating non‐stationary or low‐frequency‐dominant scaling within the fitted range. Regional assessments revealed that precipitation deficits were more evident in the inland semi‐arid regions, namely, Central Anatolia, Eastern Anatolia, and Southeastern Anatolia. In the humid coastal regions, increasing drought trends were more clearly expressed in the SPEI series that includes the evaporative demand. Overall, these results show a shift toward more persistent drought‐prone hydroclimatic conditions in Türkiye, particularly in the SPEI‐based climatic water‐balance series.