Prevailing and Maximum Drought Intervals in the Iraqi Mesopotamia Plain Region: Index-Based Estimation

Drought indices are an effective tool for evaluating the impact of drought on environments, such as its duration and severity. Here, monitoring and evaluation of meteorological drought were conducted for 3-decades (1984-2014) in the Mesopotamia Plain Region in Iraq using the Drought Indices Calculator DrinC1.7(91) software based on monthly precipitation data recorded by thirteen stations covering the overall study area. The calculations for the standardised precipitation index (SPI), the exceedance probability, the frequency of repetitions of consecutive drought years, and the return period were conducted. Results revealed that the general average drought level was moderately dry, and in most parts of the study region, the percentage of rainy years is less than the dry years, where, on the average annual yearly scale, it is 40% for rainy years and 60% for the dry years. Moreover, the exceedance probability and the frequency decrease when the drought interval increases and the dominant event is a one-year drought and the maximum drought interval occurred within the return period of 3-decades was eight consecutive years (1998-2006), with a 3.33% exceedance probability.