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An examination of dry season in western Iran from 1966 to 2000 is displayed utilizing month to month precipitation information watched at 140 gages consistently dispersed over the region. Dry spell conditions have been surveyed by implies of the Standardized Precipitation List (SPI). To consider the long-term dry season changeability the foremost component investigation was connected to the SPI field computed on 12-month time scale. The investigation appears that applying an orthogonal turn to the primary two central component designs, two unmistakable sub-regions having diverse climatic inconstancy may be distinguished. Comes about have been compared to those gotten for the large-scale utilizing re-analysis information proposing a palatable assention [1]. Moreover, the expansion of the large-scale examination to a longer period (1948–2007) appears that the spatial designs and the related time inconstancy of dry spell are subjected to discernible changes. At long last, the relationship between hydrological dry seasons within the two sub-regions and El Niño Southern Oscillation occasions has been explored finding that there's not clear prove for a connect between the two wonders.

Dry season frequencies, in any case their seriousness, have became more common in later a long time in parallel with global climate changes. Dry season could be a continuous wonder, gradually taking hold of an range and fixing its grasp with time. Some of the time, in extreme cases, dry season can final for numerous a long time and can have obliterating impacts on the socioeconomic, rural, and natural conditions which will result from one or more of the water-scarcity components by deficiently precipitation, tall evapotranspiration, and over-exploitation of water assets [2]. With respect to physical geology, Iran has parched and semi-arid climates generally characterized by precipitation and tall potential evapotranspiration. The normal yearly precipitation over the nation is evaluated to be around 250 mm, happening for the most part from October to Walk. Yearly precipitation is lower within the eastern half of Iran compared with the western half [3].

Dry season occasions and the precipitation deficiency result in numerous normal challenges, and characterize the climatic behaviour all through this nation. Dry season yearly hits most Iranian areas. This was especially the case amid the later spell of 1999-2002 which was the most exceedingly bad dry spell occasion since 1950 to the display. Generally, droughts can be classified into rural, hydrological or meteorological in which maintaining a strategic distance from meteorological dry season is outlandish; in any case, they can be anticipated and observed to reduce their antagonistic impacts .To measure dry season and screen its development, numerous dry spell lists have been created and connected. A expansive number of dry season files have been recommended to date, counting Palmer Dry spell Disjoinity Record, Edit Dampness file, Agro-hydro Potential, Surface Water Supply Record, vegetative dry season record of Normalized Contrast Vegetations List, Standardized Precipitation List , Deciles , and different lists of moo stream stream [4].