Spatial Assessment of Drought Conditions Over Iraq Using the Standardized Precipitation Index (SPI) and GIS Techniques

Abstract

Iraq is located between latitudes 29o 00′ to 37o 15′N and longitudes 38o 45′ to 48o 25′E and covering an area of 438,320 km2. The topography of Iraq consists of alluvial plain in the middle and south parts and desert plateau in the west as well as rising terrain to the mountain ranges in north and northeast parts of Iraq. The geographical location and topographic diversity are induced a climate variation over Iraq. The current study aims to use the standardized precipitation index (SPI) in the evaluation of drought conditions based on long-term monthly precipitation data during the period between 1980 and 2010, collected from 18 weather stations. SPI values at five accumulated periods, i.e., 3, 6, 9, 12, and 24-month are calculated using SPI software developed by National Drought Mitigation Center, University of Nebraska-Lincoln. Average SPI values and SPI frequencies for wet and dry conditions are calculated with Microsoft Excel software and analyzed using GIS techniques. Results of spatial interpolation of SPI values are presented with maps and time series graphs. Analysis of the results shows the wet and drought conditions are periodic and alternative at most of the Iraqi regions. The SPI values show wide ranges of variation in their durations and magnitudes at all weather stations. Frequency percentage of SPI values show high variations have reached up to 20% for wet conditions, 22% of dry conditions and the rest is near normal conditions. Time series analyses for the graphs of SPI at different stations insured the trends toward increasing drought and repeated periodic dry and wet conditions over Iraq. That means the agricultural, hydrological and socioeconomic situations in Iraq will face many crises in future.