Investigating and Analyzing the Drought Trend in the Givi Dam Catchment with a Multiple Index Approach

Assessing the drought situation and formation trend has always been one of the important factors to deal with the devastating effects of this phenomenon. Different index are used to determine the drought, depending on location in specific periods. The main purpose of this study is to assess the drought situation of Givi Dam Catchment with the multiple index approach. Accordingly, this phenomenon was analyzed using the precipitation data of the two selected stations in the Givi Dam Catchment during a 31-year statistical period, using SPI, RDI, CZI, SZI, PNI, and DI. The results showed that severe drought occurred in 2005, 2008, and 2013 in Khalkhal station and 2013 and 2017 in Firoozabad station. Moreover, using the Effective Drought Index (EDI), the number of dry days was obtained in the fall and winter seasons of the years with severe drought. By examining the indicators monthly, it became clear that despite the relatively high similarity of SPI, CZI, SZI, and RDI in showing the main drought and wet periods, SPI is more effective in detecting the onset of drought periods than the other indices.