New lights on the groundwater settings of El-Kharga Oasis under over-pumping conditions, the Egyptian Western Desert

Abstract Evaluating the conditions of groundwater aquifers periodically, along with good management of the withdrawal and use of groundwater aquifers, is considered extremely important. The current study uses pumping test data to re-evaluate and determine the extent of change in the Nubian Sandstone Aquifer System (NSAS) conditions with over-pumping operations, as it is considered the main aquifer in El-Kharga Oasis, Egypt. The study area experiences high drawdowns and a marked decrease in Piezometric Heads due to heavy exploitation. Twenty-one pumping and recovery tests were analyzed to obtain the Hydraulic parameters of the groundwater aquifer. In addition, the depths and levels of fourteen groundwater wells were measured to assess the water movement patterns and the distribution of the Hydraulic Heads in El-Kharga Oasis. The results show that the effective porosity of the NSAS varies from 21.7 to 28.3%, with an average of 24.7%. These values were used to estimate the Hydraulic Conductivity, which varies from 3.8 m/d to 16.1 m/d with an average of 8.07 m/d. Transmissivity values range from 75.6 to 1440 m 2 /d, and the Storativity range from 0.00000028 to 0.01125. The Transmissivity and Hydraulic Conductivity values in the study area show that sand is the main component of the groundwater layers. According to the Transmissivity values, the NSAS has moderate to high potential. The Hydraulic Head measurements vary from -22.5 m. in the center eastern part to 85.6 m. in the southwest. Groundwater flows from southwest to northeast, westward, and north to southwest in the southern, central, and northern parts. The results are beneficial for estimating groundwater aquifer potentials in El-Kharga Oasis.