ABSTRACT
Box 5.3 Saltwater intrusion The groundwater is fresh at the landward side and salty at the seaward side. The freshwater/seawater interface is quite abrupt and is usually close to the shore. Its position depends on the rate at which the freshwater can drain towards the sea. The seaward flow of freshwater prevents the landward flow of saltwater and there is an equilibrium position, which has slight variations due to tides and season. If water is pumped out of the freshwater side, the interface shifts and the result is saline water encroachment into the aquifer. This can reverse the flow, bringing salty water up into the wells, as shown in Figure 5.8. Alterations to the freshwater regime, through dam construction and land-use or climate change (e.g. more or less moisture) may change the position of the interface.
