Intensity-Duration-Frequency and spatial analysis of droughts using the Standardized Precipitation Index
M. Mohseni Saravi1, A. A. Safdari1, and A. Malekian21Faculty of Natural Resources, University of Tehran, Karaj, Iran 2International Research Center for Coexistence with Desert, University of Tehran, Tehran, Iran
Received: 15 Jan 2009 – Accepted for review: 30 Jan 2009 – Discussion started: 02 Mar 2009
Abstract. Precipitation deficit and its daily, seasonal and annual oscillations are inherent characteristics of Iran's climate. Droughts are generally characterized by a prolonged and abnormal moisture deficiency. In drought studies it is important to characterize the start and end of a drought as well as its intensity, duration, frequency and magnitude. The objective of this study was to analyze drought characteristics and to develop drought maps in the Karoon river basin, Iran. The Standardized Precipitation Index (SPI) was used in drought analysis based on the data for meteorological stations located inside or adjacent to the study area and three time scales including the 3-, 6- and 12-month SPI were evaluated. After determining the dry and wet periods, historical characteristics of droughts were identified and spatial distribution maps of droughts were plotted using GIS. Based on frequency distributions, drought durations and magnitudes were computed corresponding to 5, 10, 20, 50 and 100-year return periods. The Time scale-Duration-Frequency (TDF) and Time scale-Magnitude-Frequency (TMF) relationships were also developed, which constitute an essential tool for water resource design purposes. Drought spatial distribution maps show that extreme conditions dominate the southeastern regions of the basin. The efficiency of the SPI is determined by monitoring the drought of 1999.
Mohseni Saravi, M., Safdari, A. A., and Malekian, A.: Intensity-Duration-Frequency and spatial analysis of droughts using the Standardized Precipitation Index, Hydrol. Earth Syst. Sci. Discuss., 6, 1347-1383, doi:10.5194/hessd-6-1347-2009, 2009.