From the hydrogeological and geochemical conceptualisation to the groundwater management: the Gioia Tauro Plain (Southern Italy)

The Gioia Tauro plain (GTP) is an industrialized and agricultural coastal area of about 500 km² in the Tyrrhenian side of Calabria. Its harbour is one of the most important container traffic hubs in the Mediterranean basin. The GTP groundwater resources are constantly at risk of depletion and quality degradation due to anthropic activities.

GTP is a half-graben bounded by two massifs. The boundaries are marked by three main fault systems: the Nicotera-Gioiosa fault zone, NW-SE striking and right lateral kinematics along the north boundary; the NNE-SSW Cittanova Fault, a high-angle normal and active fault along the eastern border; the Palmi-Locri fault zone with NW-SE trend and a mainly strike-slip kinematics along the south boundary. The GTP sedimentary infill is made by an upper Miocene siliciclastic and carbonate succession overlays by Pliocene marly-limestone rhytmites and Piacenzian-Calabrian sandstones and calcarenites with interbedded 20m thick volcaniclastic deposits. Upward, the sedimentary infill continues with alluvial (in eastern and middle sector) and coastal (in the western sector) deposits.

Six geochemical facies of groundwater were distinguished, with different salinities and temperatures (Italiano et al., 2010). The majority of samples is of cold shallow groundwater and shows Ca-HCO₃, Ca(Mg-Na)-HCO₃(Cl-SO₄) and Na-HCO₃ composition and overall low salinities (TDS <1g / L). Only few samples, with Na-SO₄ and Na-Cl composition, show high salinity (TDS <3.5g / L) and temperature (above 20 ° C). These latter occur in the northern portion of the plain, near the intersection of the Palmi-Gioia Tauro and Nicotera-Gioiosa faults systems, and in the southern sector, near Palmi town.

It was created a geodatabase using data of hundreds of boreholes, geotechnical and geophysical investigations. Furthermore, it is carrying out a geological and geophysical survey along the plain boundaries using passive seismic technique to infer the deep of discontinuities among the main geological units described above. The acquired data allowed to identify: i) the shallow aquifer, made by Pleistocene-Holocene deposits characterized by complex lateral variations; ii) at the bottom, the aquitard, represented by Pliocene marls; iii) the deep aquifer, consisting of the upper Miocene succession. The highest thickness of shallow aquifer (more than 200 m) is observed in the middle GTP sector. The thickness variation is strictly related to the NE-SW high angle normal faults which cross the GTP. The ongoing geological, geochemical, and geophysical surveys will allow: i) to identify the geometry of the hydrogeological units; ii) to define the hydrogeological features of the groundwater systems useful for modelling purposes, and iii) to improve the knowledge of water rock interactions processes (e.g., relations between deep and shallow waters, anthropogenic effects, seawater intrusion) for management purposes.

Italiano, F. et al. 2010. Geochemistry of fluids discharged over the seismic area of the Southern Apennines (Calabria region, Southern Italy): Implications for fluid-fault relationships. Appl. Geochem. 25, 540–554.