seawater intrusion
In coastal aquifers, the less dense fresh water lies above a wedge of salt water, and is separated from it by a mobile transition zone. Small changes in the fresh water level can bring about large changes in the transition zone; a 1 m drop in the fresh water-table typically results in a 40 m rise in the transition zone. Thus, when groundwater is extracted more rapidly than it can be recharged, there can be a significant seawater incursion, so that well water often becomes saline. This is a major problem, in, for example, north-east Crete, as an effect of the rapid development of package tourism in a semi-arid environment.
