Preface: Saltwater and freshwater interactions in coastal aquifers

Abstract

The study of coastal aquifers, i.e., aquifers that have a hydraulic connection with a saline surface-water body, forms a somewhat separate discipline in groundwater science. This type of aquifer is typically characterized by variations of groundwater salinity in space and time, which warrants special treatment of groundwater flow, groundwater chemistry and water resource management problems. The interest in the study of this type of aquifer arose both from its strategic importance for the water supply of highly populated coastal areas and its suscept- ibility to salinization problems. Saltwater intrusion, i.e., the displacement of fresh groundwater by groundwater with a higher salinity, has become an accepted scientific term in the research field. Coastal aquifers and the interactions between fresh and saline groundwaters are the topic of this theme issue of Hydrogeology Journal. We decided to give this issue a twofold objective. On one hand, it is meant to present a series of papers that together demonstrate the state of the art of the research in coastal hydrogeology. On the other hand, the aim is to present a review of the extent of saltwater-intrusion problems around the world.