Investigation of Temporal Relation between Occurrence of Meteorological and Hydrological Droughts (Case study: Bilverdi-Doozduzan Basin)

Due to the importance of water resources and their qualitative and quantitative effects on ecosystems and biological activities, study about drought is very necessary for water resources management. The aim of this study was to determine the temporal relation between the occurrence of meteorological and hydrological droughts in Bilverdi-Doozdoozan basin during a 16-year period, using precipitation and surface flow data obtained from 4 climatic and 4 hydrometric stations. For this purpose, the Standardized Precipitation Index (SPI) and Standardized Run-off Index (SRI) were used. The maximum correlation between meteorological and hydrological droughts (at 99% confidence level) was found for 6 month time intervals. Also the results gained from investigating regional meteorological drought and hydrological drought in basin outlet, indicated the maximum correlation at confidence level of 99% (r=0.771) in 9 month time interval. The results indicated that the distance from precipitation and hydrometric stations, geographical properties and basin topography were effective factors in the investigation of two drought indices relation.