Contribution to the hydrogeology of Six Hills sandstone aquifer in East El-Oweinat area, south Western desert, Egypt

El-Oweinat area is located in southwestern Egypt and is considered to be one of the new land reclamation projects in the Western Desert. The Nubian Sandstone aquifer has high potentiality and good groundwater quality. The results of geologic and hydrogeologic studies reveal that the Six Hills sandstone aquifer represents the sole groundwater resource used for all purposes (agriculture, drinking, domestic, livestock and poultry) in East El-Oweinat area. The Six Hills sandstone aquifer overlies directly the Precambrian basement rocks. The concerned aquifer exists under unconfined conditions as it is exposed on the surface. The hydrogeological cross sections show that the fully saturated thickness of the Six Hills sandstone aquifer ranges between 150.2 m and 651 m and increases towards the west. The groundwater generally flows towards the northeast direction with an average hydraulic gradient of 0.6 ‰. The calculated groundwater volume of the Six Hills sandstone aquifer in East El-Oweinat area (4,340 km2) reaches 350 bcm of fresh water. The comparison of the depth to water in the same monitoring wells during 14 years (2003 and 2016) reveals that the head decline rate in groundwater depths were ranging between 5 cm/year and 80 cm/year. The pumping rate increased from 600,000 m3/day in year 2003 to 3,600,000 m3/day in 2016. The average transmissivity attains 2,060 m2/day reflecting the high potential of the Six Hills sandstone aquifer in East El-Oweinat area. The groundwater flow model (MODFLOW) has been used to investigate the impact of groundwater withdrawal on groundwater levels for sustainable groundwater management. Four scenarios were applied to predict the probable head changes in the Six Hills sandstone aquifer and their impact on the availability of groundwater. The fourth scenario is recommended in order to sustain the groundwater resources in the study area and keep the drawdown rates in the range of 0.66 m/year through reducing the present discharging rates (10,000 m3/day/well) by about 40%.