Controlling Seawater Intrusion Beneath Coastal Cities

Coastal plains are found on all continents, and are regional features bounded on the continental side by highlands and on the seaward side by a coastline. Many urban settlements are located on coastal plains, and many of these rely on underlying groundwater for water supplies. Saltwater intrusion (the invasion of freshwater by saltwater from the sea or from marine deposits due to groundwater withdrawal) threatens groundwater supplies in many such areas. The encroachment of saltwater into freshwater supplies has become a cause for concern over the last century as populations in coastal areas have risen sharply and placed greater demands on fresh groundwater reserves. Saltwater intrusion causes many problems in these areas, perhaps the most severe being the limitation of potable drinking water. This critical problem requires appropriate management solutions. Four basic components are necessary: investigation, monitoring, modelling, and control and prevention. These four tasks must be integrated within a cost-effective framework. Such an approach should facilitate the sustainable utilisation of groundwater resources in coastal urban areas.