Assessment of meteorological and hydrological drought using drought indices: SPI and SSI in eastern Slovakia

Abstract

The current article presents a one-dimensional frequency analysis of historical drought events in the years 1972 to 2014 in the eastern part of Slovakia. Two physical drought types: meteorological and hydrological are classified by SPI – standardized precipitation index and SSI – standardized streamflow index. These indexes have the same mathematical calculation, the difference is only in the input initial monitored data collected from seven rain gauge stations and seven river stations. The most appropriate theoretical probability distribution of selected data is performed using the Kolmogorov-Smirnov test, which is done in EasyFitt program. The basic parameters of meteorological and hydrological drought are determined by the application of the RUN method. One – dimensional frequency analysis of two physical droughts is created for a purpose of estimating the probability of their occurrence in time and identifying the spatial vulnerability of this area. The main benefit of this work is the identification of the average return time of drought events. On average we can expect a moderate meteorological drought in 18.14 to 36.8 months and a hydrological drought in 26 to 60 months.