PHENOMENA RELATED TO THE VARIATION OF EOUILIBRIA BETWEEN FRESH AND SALT WATER IN THE COASTAL KARST-CARBONATE AQUIFER OF THE SALENTO PENINSULA

The state of saline intrusion brought about by uncontrolled abstraction from the coastal carbonate-karst aquifer in the Salento Peninsula is monitored by means of a series of observation wells scattered throughout the territory and drilled at different times during the last 20 years. One of the methods of determining the state of non-equilibrium between fresh and salt water is based on the observation of the actual hydraulic head compared with the theoretical head that the groundwater should have, taking into account the real position of the transition zone; in this way a non- equilibrium index can be determined. Moreover, by means of the plots of salinity against depth, it is possible to calculate the theoretical position of the salt water interface and if this is supposed to be sharp instead of a gradual transition. The relationship between the level of the theoretical sharp interface and the actual head of fresh groundwater seems to be related to the value of the non- equilibrium index.