Analysis of Changes in Spatial Pattern of Drought Using RDI Index in south of Iran Abdol Rassoul Zarei 1 & Mohammad Mehdi Moghimi 1 & Mohammad Reza Mahmoudi 1 Received: 13 March 2016 /Accepted: 27 May 2016 # Springer Science+Business Media Dordrecht 2016 Abstract Drought is one of the main natural hazards affecting the economy and the environ- ment of large areas. Droughts cause crop losses, urban water supply shortages, social alarm, degradation and desertification. In this study, the spatial characteristics of annual and seasonal drought were evaluated based on climate data from 16 synoptic stations during the period of 1980–2010 in south of Iran. To estimate the drought severity used modified Reconnaissance Drought Index (RDI) and to prepare maps, ArcGis10.2 software was used. Results showed in annual drought, percent of areas with normal condition, severe dry and extreme dry condition have had significant increasing trend (0.95 level). In winter drought, the percentage of areas with severe dry and extreme dry condition have had significant increasing trend (0.95 level). In spring drought, percent of areas with moderate dry has had significant increasing trend (0.95 level), in summer drought, percent of areas with moderate dry has had increasing trend (insignificant) and in autumn drought, percent of areas with severe dry has had significant increasing trend (0.95 level). Other classes of drought in different time scales had not significant trend. Result showed that the percentage of area with dry condition is increasing, this can be effective on the agricultural activities, agricultural productions, water resource management and other activities. Keywords RDI index . Drought . Spatial pattern . GIS . Trend of changes 1 Introduction Drought is considered as one of the most costly and least understood natural disasters (Kao and Rao 2008). It is a global phenomenon that can occurs in all types of landscapes. Water Resour Manage DOI 10.1007/s11269-016-1380-0 * Abdol Rassoul Zarei Ar_Zareiee@Fasau.ac.ir 1 Fasa University, Fasa, Fars, Islamic Republic of Iran