Hydrological Drought Analysis Using SDI Index in Halilrud Basin of Iran

Nowadays, drought is considered as damaging environmental phenomenon which affects natural resources and social communities. therefore, it is important to assess the magnitude and effects of these phenomena and consider it in the relevant management efforts. to do this we used l-moment method for regional homogeneity testing. the stream-flow drought index (sdi) as a hydrologic drought was used for investigating probability of drought occurrence in halilrud basin as one of the important basins in arid and semi-arid regions of iran. this area annually suffers from drought damages. results showed that drought magnitude range is varied from mild to severe across basin from upstream to downstream. frequency of drought occurrence is concentrated in southern of basin. results also showed high correlation between standardized precipitation index (spi) as a meteorological index with hydrologic index (sdi).