Drought, Time Multivariate Index, Principal Components Analysis

In order to avoid drought effects، it is essential to detect and monitor the spatial and temporal changes of the phenomenon. Generally، drought indices are used to achieve these goals. The main aim of this paper is to introduce and assess a new drought index named MRDI. The Modified Reconnaissance Drought Index (MRDI) is then compared with the Modified Standardized Precipitation Index (MSPI)، based on the Standardized Precipitation Index (SPI) and the Reconnaissance Drought Index (RDI)، involving well known statistical technique named Principal Component Analysis (PCA) in Gorganroud basin، Iran، as a case study. According to the results، the new MRDI and also MSPI multivariate indices have shown more accurate results and are also easier to use than the SPI and RDI univariant indices. Comparison of MRDI and MSPI results، based on the non-parametric Kolmogorov–Smirnov test in Gorganroud basin، has shown that، there is no significant difference between them and their behaviour is similar in more than 90% of the cases. Evaluation of the latter result needs to repeat this study in more reagent basins.