RDI as the appropriate index of drought monitoring system in water resources management in Iran

Assessment of drought events for different regions of Iran is essential in water resources planning and project management. Considering the arid and semi-arid climatic features in Iran, the country has been prone to many severe drought events in the past. As a result, in addition to the precipitation variable, it would seem appropriate to include some other aspect of the climatic features in drought analysis. The RDI index by including the potential evapotranspiration, as an additional meteorological parameter exhibits significant advantages over other indices such as the SPI index. In the present study the Reconnaissance Drought Index (RDI) is used together with the well known Standardized Precipitation Index (SPI). Data with more than 30 years of information from 39 synoptic stations in different parts of Iran were used for the period of 1967-2005. The results show that the RDI generally responds in a similar fashion to the SPI. However, in some months increase or decrease in evapotranspiration will cause significant variation between the two indices. Furthermore, the RDI is more sensitive to climatic variability by including the role of evapotranspiration, to explain drought events. Based on the findings of this research, it is recommended that the RDI index should be used as the proper drought index in the monitoring system for water resources planning and management in Iran.