Hydrological Assessment of Iraq for the Period 2002-2020 Using GRACE Terrestrial Water Storage Deficit

Abstract

The research examines the effectiveness of remote sensing for monitoring drought conditions, specifically focusing on the utilization of satellite missions like GRACE to detect alterations in water levels. The study analyzes GRACE data for 10 Jet Propulsion Laboratory (JPL) grid cells alongside precipitation data from 11 meteorological stations. It employs the DrinC program to calculate the standard precipitation index (SPI) at different time intervals. Non- Non-parametric Mann-Kendall tests and Sen's slope statistics are used to determine the trend and magnitude of the GRACE-based anomaly in terrestrial water storage. The statistical findings reveal a significant decrease in Iraq's terrestrial water storage anomaly between 2007 and 2017, indicating drier climatic conditions. However, there is an increase in anomaly between 2002 and 2006, as well as from 2018 to 2020, indicating wetter conditions. The water storage deficit varies among grid cells, each exhibiting distinct characteristics and patterns. The study also highlights that more intense and prolonged droughts tend to occur in the northern and southern regions of Iraq, while the central region experiences more frequent but less severe droughts. In most grid cells, the Mann-Kendall test illustrates a substantial decrease in the water storage deficit index and a significant increase in SPI-06. On the other hand, only one grid cell shows a noticeable precipitation trend. Comparatively, trends in the water storage deficit index and SPI-06 are similar. Overall, the water storage deficit and its index prove valuable in predicting drought severity in locations lacking hydrological measurements.