Assessment of seawater intrusion and groundwater mineralization in coastal aquifers of north-eastern Algeria

Seawater intrusion into freshwater aquifers occurs mainly in coastal areas due to the excessive groundwater extraction, lowering the water table. In north-eastern Algeria, seawater intrusion exerts a significant influence on the coastal aquifers of Annaba and Guerbes, leading to highly variable and generally elevated salinity levels. Electrical conductivity in inspected regions ranges from 0.2 to 15 mS·cm−1, with an average of 1.9 mS·cm−1. Annaba aquifers have the highest conductivities in the plain areas near the Mediterranean Sea and along the rivers draining the plain. Conversely, the Guerbes aquifer displays a different pattern, with lower conductivities in the inner zones that increase along the streams toward the coast. Chemical analyses of water samples indicate that sodium chloride and calcium chloride facies are predominant. The concentrations of chemical trace elements (Sr2+, Li+, Br−) and major ions were analyzed to elucidate the salinity behavior of these coastal aquifers. The findings suggest that the mineralization of groundwater in the Annaba and Guerbes aquifers is influenced by four primary sources: dissolution–precipitation processes of aquifer rocks, the upward movement of saline deep water in fault zones, infiltration of irrigation water, and marine influences, including seawater intrusion, aerosols, and sea spray.