Recharge flux to the Nubian Sandstone aquifer and its impact on the present development in southwest Egypt

•We collect the hydrological data of wells in the study area.•The water table of the Nubian aquifer is subject to continuous decline.•We carry out groundwater flow model using FEFLOW.•The results indicate that the length of the southwest flux boundary is about 170 km.•Implementation of 1600 proposed wells shows lowering of water table (5–15 m) in time period of 27 years.

The southwestern part of Egypt (East El Oweinat) is an arid area with no surface water and only one resource of useable groundwater in the well-known Nubian Sandstone aquifer. This resource has been heavily exploited since 1990, which has led to a continuous decline in the potentiometric surface of this aquifer. The groundwater recharge in the concerned area depends exclusively on the subsurface inflow across the Egyptian/Sudanese borders. A FEFLOW, finite element groundwater model, has been used to investigate the length of the recharge window and to predict the hydrodynamic impacts of different groundwater extractions on the potentiometry of this aquifer. A complete database of the hydrogeological and drilling information of about 600 water wells drilled in the period 1985–2010 was evaluated and used for the model parameter input as well as for its simulation. The results of steady-state simulation indicate that the length of the southwest flux boundary is about 170 km with angle flow direction about 52°NW with a groundwater flow rate about 0.018 m/day. A calibrated regional numerical model with refined grid on the pumping centres, hydraulic properties and flux boundary in the southwest is used to simulate the impacts of the present and planned groundwater extraction on the potentiometry of the aquifer. The results show a real danger of increasing the water depth to uneconomic lifting depth. Through implementation of 135 pumping wells in time 2002–2008, the lowering of water table ranges from 1 to 1.5 m in the reclamation areas. On the other hand, the distribution of 1600 proposed wells with distance between every two adjacent wells not less than 2700 m indicates that the lowering of water table ranges from 5 m away of the reclamation areas to 15 m in the reclamation areas in time period of 27 years (2008–2035). This result seems to be the better for the present irrigation project in East El Oweinat area.