Drought Condition Severity and Zoning based on Rainfall Anomaly Index (RAI) in Fars Province

One of the main problems that the human beings are facing these days, is the occurrence of the hydrological droughts and the resulting water crisis. Since the hydrological droughts happen gradually and have long term effects, drought monitoring is of a high importance. Among the indices of drought monitoring, the rainfall abnormality index (RAI) is being widely employed because of its simplicity and high accuracy. The required precipitation data have been gathered from 10 hydrometric stations with an appropriate distribution in the studied region, including the Kazeroun, Dasht Arjan, Farashband, Band Bahman, Jahrom, Joukan, Bovanat, Kaftar Lake, Ghalat, and Neyreez stations. The gathered data are for a statistical period of over 20 years from 1991 to 2011. The drought zoning diagrams are presented for long periods and the most severe droughts are determined. The results revealed that in all stations¡ generally and roughly, drought occurred sporadically in the form of a 1-year periods between 1991 and 2001. And between 2002 and 2011 drought, mostly occurred in the form of multi-year long periods. Based on the RAI¡ the two most severe droughts occurred in 2000 in Jahrom station showing an index value of -3.94 and in 1994 in Kazeroun station with an index value of -3.87. Moreover, RAI shows that the most precipitation was recorded in 1996 in Neyreez station with an index value of 4.63.