Demand for water is on the rise everywhere in the world, particularly in arid and semiarid countries including Iran. Arid and semiarid regions suffer from droughts. The goal of this study is to predict the standardised precipitation index (SPI) for future drought intensity in Beheshtabad watershed, Karun basin, which is located in central Iran. Daily climate series were produced using the recorded data of Shahrekord gaging station of a reference period (1961–1990). Hadley Center Climate Model 3 general circulation model (GCM) with one greenhouse gas emission scenario (A2) has been used to construct daily climate precipitation time series over three future periods (20102039, 2040–2069 and 2070–2099). The statistical downscaling model (SDSM) was used to downscale GCM output. SPI for three 30–year future time series was determined on 3, 6, 9 and 12 months. The results indicate that at short time scales, the drought series have a high frequency of drought and short duration instead the SPI values of longer time scale had an extended range with low frequency of drought. The results indicated that the severity of droughts do not solely depend on the values of drought index and also depends on duration. The results show that an increase in duration and magnitude of droughts in the third future period is more than the second and initial future periods.
Keywords: standardised precipitation index, SPI, general circulation model, GCM, statistical downscaling model, SDSM, drought prediction, Beheshatabad watershed, Iran, drought intensity, drought severity, rainfall