A new approach for characterization of meteorological and hydrological droughts: Cumulative standardized drought index (CSDI)

Identifying drought events and their characteristics for a river watershed that provides drinking water for metropolitan centers is crucial to sustaining water resources management. In this study, Cumulative Standardized Drought Index (CSDI) is developed to examine the effect of previous dry or wet periods on the characteristics of the drought event. Meteorological and hydrological droughts of the Gordes and Tahtali watersheds, which provide a significant part of the drinking water of Izmir, Turkey, determined for 1, 3, 6 and 12 month time scale by CSDI. The peak turning points of CSDI according to time show the transition from wet to dry period, whereas the lowest turning points do the transition from dry to wet period. Cumulative sum (CUSUM), Pettitt and means square error (MSE) analyzes are used to determine whether the turning points are significant turning point. As a result of the study, the characteristics of dry events, duration, magnitude and intensity, are determined with CSDI, especially those occurring at short time scales such as 1 and 3 months. In addition, the characteristics of meteorological and hydrological droughts observed at 12 month time scale are determined with the CSDI method and the Run Theory and comparisons were made in the study. As a result of the comparison, it is found that drought events, which seem to be different drought periods, indicate a single period when the effect of the past periods is considered. It is shown that the CSDI method can be used adequately to determine the dry and wet periods and their characteristics of the watersheds.

Automated summary

In this study, the Cumulative Standardized Drought Index (CSDI) is developed to examine the impact of past dry or wet periods on the characteristics of drought events. The CSDI is used to determine meteorological and hydrological droughts in the Gordes and Tahtali watersheds in Izmir, Turkey, at different time scales. The results show that the CSDI method is effective in identifying the dry and wet periods and their characteristics in the watersheds.