Analysis of changes trend in spatial and temporal pattern of drought over south of Iran using standardized precipitation index (SPI)

Abstract

In this research, the precipitation data of 16 synoptic stations from 1980 to 2014 in the south of Iran were used to evaluate the changes of the spatial and temporal pattern of drought based on the SPI index. Results of changes trend analysis in the temporal pattern based on linear regression (LR) showed that the most droughts occurred in the annual time scale (at 37.5% of stations). Based on Mann–Kendall (MK) and Spearman’s Rho (SR) tests, the most drought trends occurred in winter and annual time scales. Analysis of spatial pattern changes of drought showed that percent of areas in all classes of drought and all-time scales had non-significant changes (based on MK test), according to SR test, only the areas in moderate wet class of drought had a significant decreasing trend at 5% level. Analysis of LR test showed that the percent of areas in all classes of drought in seasonal time scales had non-significant changes, in annual time scale severe dry and extreme dry classes had a significant decreasing trend at 5% level. Generally, results showed that area percentage with dry classes had an increasing trend, therefore the study area is going to be drier and it’s effective on agricultural activities, natural resources management, surface water resources and underground water resources planning and other activities.