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Abstract

The main objective of this study was to determine the relationship between two different multi-scalar meteorological drought indices (SPI and SPEI) and hydrological drought index (standardized streamflow index, SSI) associating with socio-economic drought impacts in Tehran Province, Iran. In view of this, in the first step, the comparison of two meteorological droughts showed that both SPI and SPEI indices have significant correlation, moreover the SPEI showed the quick response to drought. The increasing the timescales of indices also increase the duration of drought. Based on the importance of evapotranspiration in arid and semi-arid regions, the SPEI can be used as a suitable index in determining drought type’s relation. After investigating adeptness of SPEI, in the second step, to determine the meteorological and hydrologic droughts relationship, 12 catchments that have meteorological and hydrometric stations with the same long-term data (meteorological and streamflow (discharge)) were selected. In this 12 catchments SPEI and SSI were determined. The results showed a weak relation between meteorological and hydrological drought indices that maybe caused by a lag time between two types of droughts, but the trend of two types of droughts is similar. In the third step, to investigate relationship between drought indices and socio-economic variables, in each of catchment, two socio-economic indices comprising crop field area and population were determined. The results showed that increasing drought intensity cause a significant decreasing in crop field area, whereas there is not a significant relationship between population and drought indices.