Saltwater intrusion in coastal Lebanon: evolution of patterns, and database for groundwater quality monitoring and management

Half a century after the only national-scale report on saltwater intrusion (SWI) in Lebanon, the evolution of this hazard is re-examined. SWI proxies from 4000+ field measurements and chemical samplings are collected from a network of 276 sites. To interpret this dataset, the coast is divided into seven large coastal areas which are then sub-divided into 14 smaller coastal hydrogeological zones (CHZs) reflecting uniform hydrogeological conditions and properties. Hydrochemical analyses characterized the groundwater types of the coast. Fresh–brackish to brackish–salt NaCl or CaCl water types attaining elevated salt content are present in several zones, and ongoing salinization to variable extents affects four CHZs. Porous-unconsolidated aquifers suffered the largest salinization spread compared to fractured karstic aquifers. Over-pumping is the main SWI driver in many zones. Comparing to older results, fast-ascending SWI impacts most coastal groundwater resources. The database from this study is shared to serve urgently needed continuous monitoring of SWI proxies and groundwater resources management.