Quantifying Meteorological Drought Severity for the Watersheds in Euphrates River Basin, Central Euphrates District, Iraq

Abstract

Drought is a major natural extreme event that can cause significant damage to water resources. This study investigated the implications of drought for Watersheds in Euphrates River basin in Iraq which includes Hilla, Karbala, Najaf, Diwaniyah, and Najaf.. It was found that had an adverse impact on the study region. Among the most often used drought assessment indices globally are the Standard Precipitation Index (SPI) and its version, the Standard Precipitation and Evapotranspiration Index (SPEI).The study evaluated several probability distribution functions to model rainfall and water balance in Iraq. The Kolmogorov–Smirnov (K–S) test and the Anderson–Darling (A–D) test were used to test the goodness-of-fit for rainfall and water balance. The log-normal distribution was found to be the best fit for rainfall at approximately 40% of the stations considered, while the generalized logistic distribution (genlog) was the best fit for water balance at approximately 80% of the stations considered. The study also found that the extreme droughts in Samwah in 2012 and Diwiniyah in 1999 had the highest severity values of -2.8957 in SPI-12 and SPEI-12, respectively.