Saline intrusion and refreshening in a multilayer coastal aquifer in the Catania Plain (Sicily, Southern Italy): dynamics of degradation processes according to the hydrochemical characteristics of groundwaters

none4The Catania Plain is a large alluvial depression which represents one of the most important hydrogeological units in eastern Sicily. A detailed hydrochemical and hydrogeological investigation focussed on its north-eastern corner has provided new insights into the past and present relationship between freshwater and seawater in shallow and deep aquifers. According to hydrochemical data, over the last centuries the area has been affected by local variations of the sea level, giving rise to sequential processes of re-equilibration of the exchangeable complex, involving freshwater and seawater in both surficial and deep aquifers. These ongoing processes consist in the refreshening of both deep aquifers O500 m from the shoreline and, to a lesser extent due to lower freshwater influx, shallow aquifers. In the former case, there is a shift of the groundwater compositions towards the Na–HCO3 type and a significant drop in the salt contents, while in the latter case, the salt contents do not drop significantly. At a distance!500 m from the shoreline the exchangeable complex of deep aquifers is presently subject to salinization. According to the temporal variabilities in the hydrochemical data over the period 1995/96, the apparent dualism can be attributed to a general worsening of the current freshwater/seawater relationship in deep aquifers. This new tendency appears to be related to a sharp increase in water consumption by the local industrial plant, which has reversed the natural refreshening tendency, giving rise to a new saline intrusion that is particularly severe close to the shoreline.noneB. Capaccioni;; M. Didero; C. Paletta; L. DideroB. Capaccioni;; M. Didero; C. Paletta; L. Dider