The procedure of detecting drought trend by using Sen’s innovative trend analysis methodology

The increasing effect of drought causes negative effects on water resources. To prevent these negative effects, it is of great importance to know the trend of drought over time. Many methods are used in the literature to determine the severity of drought. One of these methods is the Standard Precipitation Index (SPI), which is calculated based on precipitation data. The SPI method was chosen in this study because it is widely used in the literature for its simplicity, flexibility, and effectiveness in characterizing drought duration and intensity. There are different classifications for drought severity in the SPI method. Therefore, it is of great importance to know the individual trends for each classification. Classical trend detection methods (such as Mann-Kendall) require a separate analysis for each drought classification. However, with Şen’s Innovative Trend Analysis (ITA) method, it becomes possible to determine the trends for all drought classifications on a single graph. In this way, the change of drought events over time can be easily determined for all drought classifications.