Multi-Index Assessment of Meteorological Drought Variability and Trends in Tuzluca District (Iğdır, Türkiye)

This study evaluated meteorological drought conditions in Tuzluca District (Iğdır, Türkiye) over the period 1960–2024 using four complementary drought indices: the Standardized Precipitation Index (SPI), Standardized Precipitation–Evapotranspiration Index (SPEI), Percent of Normal Index (PNI), and Rainfall Normalized Index (RNI), calculated at 1-, 3-, 6-, and 12-month time scales. Daily precipitation, temperature, and evaporation data obtained from the 16th Regional Directorate of the Turkish State Meteorological Service (MGM) were quality-controlled and used for index computation. The results revealed substantial temporal variability in drought and wetness conditions across short-, medium-, and long-term accumulation periods. Short-term indices (1- and 3-month) effectively captured rapid monthly and seasonal fluctuations, whereas longer accumulation periods (6- and 12-month) highlighted the persistence of extended dry and wet episodes. The longer accumulation scales revealed pronounced negative anomalies around 1999–2003 and renewed dry conditions during parts of the early 2020s. Trend analysis using the modified Mann–Kendall test identified statistically significant increasing trends in the annual mean SPI-12, PNI-12, and RNI-12 series, with Z statistics of 2.0191, 1.9997, and 2.0299, respectively (p < 0.05). In contrast, SPEI-12 exhibited a decreasing but statistically non-significant tendency (Z = −1.1451, p = 0.2522). The corresponding Sen’s slope estimates were 0.0147 index units per year for SPI-12, −0.0063 index units per year for SPEI-12, 0.3527 index units per year for PNI-12, and 0.0142 index units per year for RNI-12. These findings demonstrate that the direction and statistical significance of the detected trends differed among the indices. Overall, this study highlights the importance of combining precipitation-based and water-balance-based drought indices across multiple accumulation periods to characterize temporal drought variability and support regional water-resources management, agricultural planning, and meteorological drought early-warning systems in semi-arid regions.