Hydrogeochemical characterization and recharge dynamics of aquifers for sustainable development: a case study from the Northwestern desert of Egypt

Rapid urbanization and land cover changes in Egypt’s northwestern desert, particularly near Wadi El-Natrun, have put a strain on environmental and freshwater resources. The aquifers in the region support irrigation for more than 4201.5 km2 in the New Delta project. This study integrates remote sensing, aeromagnetic data, land subsidence probability, hydrogeology, hydrogeochemistry, and isotope analysis to assess groundwater resources, their origins, recharge potential, and land-use/land-cover (LULC) changes, to promote sustainable development. Between 1984 and 2022, 36% of the study area was converted to urban and agricultural use. Groundwater levels have dropped by approximately 5 m in the past decade. Water composition shifts from Na-HCO₃ near the Nile Delta to Na-Cl towards the south, with isotopic analysis indicating interactions between recent Nile recharge and older pluvial sources. The Wadi El-Natrun Depression captures both runoff and groundwater from these recharge areas. Groundwater flows with a hydraulic gradient of 0.3 m/km from the Nile Delta, with an annual recharge rate of 98.55 million cubic meters (Mm³), while an older recharge source from the deeper Oligocene aquifer is confirmed in the southern regions. Heavy metals and salinity remain within acceptable limits. Current groundwater extraction reaches 300 Mm³ annually. Lowering groundwater levels may reduce waterlogged areas, minimize evaporation losses, and improve the recharge mechanism of the Nile Delta. Urban extensions and development should be carefully managed, especially in the south and southwestern areas, due to the risk of land subsidence. Sustainable groundwater management within safe yields could ensure long-term water availability. Balancing extraction and recharge, the region can support continued development while mitigating environmental risks.