Author(s): M. Spiliotis; P. Angelidis; B. Papadopoulos
Keywords: No keywords
Abstract: Even if a variety of indices for assessing hydrological drought have been devised, which, in general, are data demanding and computationally intensive, rather simple and effective indices such as the Standardised Precipitation Index (SPI) have been widely used for hydrological droughts. In this article, we propose a fuzzy version of the annual Streamflow Drought Index (SDI) which is an index analogous to SPI based on the cumulative streamflow volume. The mean and the standard deviation of annual cumulative streamflow volumes are estimated as fuzzy numbers with respect to the data. This fuzzy shape of the mean and the standard deviation is based on the fuzzy estimator methodology. Thus, we can exploit the extension principle of fuzzy sets which enables us to define arithmetic operations with fuzzy sets. The proposed method was applied successfully on annual cumulative discharge of the transboundary Evros River. Useful conclusions are made from the application of the proposed method.