Integrated Geophysical and Hydrochemical Assessment of Groundwater Salinization in the Western Nile Delta, Egypt

ali abdalsalam

A total of integrated geophysical and hydrochemical investigations were conducted to characterize groundwater salinization in the western Nile Delta, Egypt. Twenty-five time-domain electromagnetic (TDEM) soundings and 30 water samples (depths 5–167 m) were used together with borehole logs and temporal comparison to 2012 datasets. One-dimensional TDEM inversion and 3-D resistivity modeling delineate six geoelectric units: a thin weathered layer (2–20 m), a shallow clayey-sand aquifer (10–40 m), a main sand aquifer (30–120 m), confining clay layers, sandy-clay horizons, and a deep conductive body interpreted as seawater intrusion. Spatial hydrochemical mapping shows TDS ranging from 388 to 9,610 mg·L⁻¹ in the shallow aquifer and 553 to 9,150 mg·L⁻¹ in the main aquifer, with nitrate hotspots (up to 948 mg·L⁻¹) associated with agricultural recharge. Temporal comparison (2012–2023) reveals intensification of salinity in the north (deep saline plume, Cl⁻ up to 3,000 mg·L⁻¹) and progressive northward encroachment. Integration of resistivity and chemistry confirms an inverse resistivity-TDS relationship, though low resistivity in some areas reflects clay rather than salinity. This study recommends targeted reductions in pumping in the northern sector, artificial recharge and hydraulic barriers where feasible, regulation of fertilizer use in the central sectors, denser geophysical surveys, and a continuous chemical monitoring program. These findings provide a replicable framework to assess salinization in deltaic, semi-arid aquifers and to guide local water-resource management.