Assessment of meteorological drought using SPI in West Azarbaijan Province, Iran

Assessment of drought is one of the most important steps in risk management of drought analysis. Drought is mostly the result of a decrease in precipitation in comparison with the mean value and would affect the quantities of soil moisture and water resources. The basis of drought indices is often based on measuring the deviation of precipitation values from long-term mean, during a specific period of time. The standard precipitation index (SPI) can be used for indicating the associated temporal and spatial variations. The aim of this research is the assessment of the characteristics such as intensity, frequency and duration of meteorological drought using SPI with 1, 3, 6, 12 and 24 months time scales in West Azarbaijan Province, Iran. The indices have been computed in various time scales for 38 gauging stations with 32 years record period in the study area and evaluated for the recent drought during 1998-2001. The results indicate that with an increase in return period and time scale, the duration of drought will be increased. Frequency of drought, with an increase in scale, will also be decreased linearly, but their durations show an increase. This index having temporal and spatial variations and is attributed as a suitable tool for analyzing drought for different hydrological purposes.