The Hydrogeological Condition of Dibdibba aquifer between Karbala and Najaf in the middle of Iraq

Abstract

The study area is located on the Dibdibba plateau in the middle of Iraq, particularly between the governorates of Karbala and Najaf. Given that the Dibdibba hydrogeological aquifer is thought to be the main source of water in this region, this site is chosen for performing the hydrogeological assessment. The study included 60 wells located on the west of the study area in Najaf Governorate. In these wells, the groundwater depths were measured in the field at the beginning of December 2021. The water stream was between 7.8 and 37.7 meters above the sea level, while the well depths ranged from 2.83 to 34 meters. Then, the spatial distribution of depths and water streams was mapped. Many wells were left by farmers because the water stream had gone down and the depth of the water had increased. The flow net of groundwater was determined to have two directions. The first direction was from the west to the east, and the second one was from the west and northwest to the southeast. The hydraulic properties of the Dibdibba aquifer in this study area were extracted by pumping tests. The experiments were carried out for five wells distributed over the area. The data was replaced with input into software for pumping tests, then analyzed by Newman's and Jacob's corrected methods for unconfined aquifers. Transmissivity values in experiments (T) ranged between 348 and 596 square meters/day, while hydraulic conductivity ranged between 14.1-22.5 m/day. The specific yield (Sy) equivalent to the storage coefficient in a confined aquifer was between 0.006 and 0.0302. The results of pumping test showed that the aquifer was of unconfined type according to the Neuman's and Jacob's corrected curves. In addition, the hydraulic property values were similar in all experiments with a slight difference, which may be related to the differences in saturated thickness, total depths, hydraulic gradient, and properties of rocks and sediments.