Comparison of drought indices in the analysis of temporal and spatial changes of climatic drought events: a case study in the Egirdir Lake basin (Isparta/Turkey)

In the Egirdir Lake Basin (Turkey), the six drought indices (i.e., SPI, PNI, DI, CZI, RAI and ZSI methods) were calculated for the three stations at 57 years between 1965 and 2022 on a 1-month and 1-year time scale. A positive correlation was determined between the drought index values calculated by the SPI, RAI, ZSI and CZI methods for three meteorological stations, even if the calculation method remains conceptually very different. Extremely dry periods and compatible results were determined in similar years according to all drought analysis methods for 1-year time scale at all stations. The RAI index gave the highest overall drought value (- 4.5) over the 1-year time scale compared to other indexes. In the analyzes of all drought methods, a very high correlation was determined for each station on a 1-year time scale. The correlation between the drought indices determined by different methods increased depending on the time scale. According to the drought analysis, it has been determined that there are dry periods for long periods, especially in recent years. It has been determined that this situation is compatible with the level drops in Egirdir Lake.