meteorological drought monitoring using the multivariate index of spei (case study: karun basin)

Considering the importance of drought in water resources management, the present study was conducted with the aim of drought monitoring using drought index spei due to its multi-scale nature and the ability to analyze at different time scales in selected meteorological stations in the karun drainage basin. another purpose of this research is to regionalize the spei index using cluster analysis method in order to homogenize the hydrologic basin. in this regard, 18 stations were selected based on the data homogeneity test and the determination of the length of the common statistical period. the spei drought index values were plotted in the form of sequencing graphs and their relationship with the correlation analysis was tested. the results showed that there is a positive and significant correlation of this index for all stations (0.5 to 0.95). also, the frequency of dry and wet periods decreases by increasing the time scale, but their continuity increases. with the regionalization of the basin stations by cluster analysis, the stations were classified into 7 classes. the results of regionalization of the spei index also showed that the frequency percentage of the normal class is higher than the wet and dry classes.