Dynamics of saltwater intrusion and submarine groundwater discharge in confined coastal aquifers: a case study in northern Israel

Many coastal areas around the world suffer severe water stresses due to improper management of water resources. In these areas, groundwater is typically the most important source for drinking water, and its overexploitation may lead to deterioration in water quality. In coastal confined aquifers, the dynamics of saltwater intrusion (SWI) and well salinization are the focus of many recent studies that commonly do not include a geological study of the subsurface structure of the aquifer. The goal of the present work is to study the effect of groundwater extraction on SWI, using the Judea Group Aquifer as a case study representing a coastal confined aquifer that suffers drawdown due to excess pumping. First, the offshore-onshore structure of the aquifer is described, and then a groundwater model is constructed based on the inferred structure. The resulting model shows that under realistic conditions, a water well situated 5 km inland from the shoreline is expected to undergo salinization after ~190 years since level drop. The SWI advances inland faster when the confinement is efficient, suggesting that semi-confined aquifers should be preferred for pumping compared with confined ones. Additionally, the model shows that under certain conditions, deep submarine groundwater discharge (SGD) occurs through the aquifer outcrop, ~15 km offshore and at depths of ~200 m. The SGD comprises brackish and warm water. The insights from this work are important both for studies on freshwater budgets in coastal areas and for the study of SGD and its implications for the ocean.