Spatio-Temporal Analysis of Drought Vulnerability using the Standardized Precipitation Index(Case study: Semnan Province, Iran)

This study was conducted to identify drought event and its emerging regions in markazi desert, iran with focus on semnan province in a 30 years statistical period. in this research, 61 stations having adequate data selected and used after extracting annual statistic from monthly and daily data. standardized precipitation index values for each station were calculated and classified. the results have shown that there was drought condition in 17 studied stations. also among 44 stations with no drought condition, there was one humid year in 20 cases. khareh sa rlazor station has the first position of drought and humid condition among other stations, with 10 drought years and 5 humid years. the number of common years with normal condition is 3 years and the most extensive drought in 1999 has occurred in 10 dry stations and i very dry station. the existence of common trend of variation using study of correlation among stations has resulted in determination of 7 groups which these results can be useful according to temporal distance of one or two years in appearing drought in the samegroup of stations.