Evaluation of Drought Temporal Changes using Mann-Kendall test and Sen’s Slope in Kerman Province for the Period 1990 to 2018

Investigating the trend of changes in drought as one of the natural disasters is essential. For this purpose, in the present study, the trend of changes in standardized precipitation-evapotranspiration drought index (SPEI) for the synoptic stations of Kerman province was evaluated for the years 1990 to 2018. The change trend of the SPEI time series was evaluated using two both Mann-Kendall and Sen' Slope trend tests. The results showed that among the study stations, Shahrbabak, located in the northwest of the province, had the highest frequency and the highest intensity of drought during the statistical period studied, with 307 drought events. The seasonal changes of drought showed that the seasonal trend of drought in spring, autumn and winter was increasing for all study stations. The incremental changes of spring drought in Anar and Baft stations were shown to be significant at the 99 level with Z-statistics of 2.72 and 2.78, respectively. The annual changes of the SPEI index also showed the upward trend of drought in all stations of Kerman province for the statistical study period. Also, the results showed that in the period of 1990-1996, the slope of the trend line of the SPEI index was positive (0.046), which indicates the reduction of drought in Kerman province during this period. Meanwhile, the slope of the SPEI index in the time periods of 1997-2010 and 2011-2018 is equal to -0.031 and -0.01, respectively, which indicates the increase in the severity of drought in Kerman province in recent years.