Delimitação geofísica eletromagnética de detalhe da intrusão salina em aqüíferos da zona costeira de Caucaia e Pecém-Ce

The present study analyses the free aquifer of the Dunes / Barreiras Formation system, at the shoreline of Caucaia and Pecém-Ce, near to the estuaries of Ceará, Juá and Cauípe rivers to the northwest of Fortaleza. This is coastal district characterized by intense tourist influx besides a considerable real state expansion. At this place there are uncontrolled focuses of salt-water intrusions, and incidences of salinizacion in saturated zone. Excessive water pumping from wells that go into salt-water wedge,<br>associated with other residual contaminations, resulted in number of abandoned wells. The coastal geomorphology has also been analyzed in order to help in the location of the saline front. Four aquifer systems were recognized: (i) dunes / paleodunes; (ii) alluvia, and (iii) sediments of the Barreiras Formation; and (iiii) Barreiras / Crystalline. Based on topography, distance, and vulnerability, these systems are contaminated at different intensities by salt-water intrusion and marine spray. The geophysical surveys (EM34-3XL and SEV) provided information about the apparent conductivity, which has been translated into water quality data, through the STD hydro chemical factor, obtained from electrical conductivities measured in wells. In addition, the isoconductivity redictive map reveals the behavior of the salt-water intrusion in respect of the distance from the salt-water front and of the preferential flow paths. All the presently achieved data, including (i) analyses of geophysical data grids of vertical and horizontal dipoles measurements (1800 records), and (ii) reinterpretation of published geophysical data, have been integrated on a Georeferential Information System (GIS). The obtained results have also contributed to the development of a methodology, which permits a precise<br>aquifer modeling. The final model allows us a permanent monitoring, even do physical or sequential changes will be occurred, either provoked by the salt-water intrusion or by leakages and waste of not determined sources.