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Coastal plain environments constantly adapt to change as a result of natural processes and increasing anthropogenic pressure, as in the case of the low relief Sibari coastal plain (Calabria, southern Italy). In order to reconstruct the hydrostratigraphic framework and explain the spatial distribution of groundwater salinization of the Sibari coastal plain, an integrated hydrogeological and geochemical approach was applied to support an accurate conceptualisation and modelling of the whole plain groundwater system. Litho-hydro-stratigraphic relationships were constructed from lithologic logs obtained from exploratory boreholes whereas, the groundwater flow system has been studied using conventional hydrogeological field investigations, hydrochemistry, and isotope hydrology. Three distinct Hydrological units (HU3-shallow aquifer, HU2 aquitard and HU1-lower aquifer) were identified showing distinct geometrical, hydrochemical and isotopic signatures. With the aim of explain the origin of Na-Cl, Ca-Cl and Na-HCO 3 waters were considered the role of ion exchange processes. The results demonstrate that values of Na + , Mg 2+ , Cl and SO 4 can be attributed to seawater intrusion, where K + is probably the major pollutant of the shallow aquifer. The adopted multidisciplinary approach provides an effective tool for accurately determination of groundwater processes and can be useful for a sustainable management of water resources in coastal plain. The physically based model of the pail groundwater system was able to explain the observed groundwater salinity variations and to support a detailed long-lasting numerical simulation of variations in the quantity and quality of groundwater resources.

Este artigo apresenta o estudo hidrogeológico e hidroquímico dos aquíferos fraturados que formam o Sistema Aquífero Serra Geral (SASG) e que estão associados a rochas vulcânicas ácidas. A região de estudo compreende parte da área do município de Carlos Barbosa, localizado na região nordeste do estado do Rio Grande do Sul. O estudo foi desenvolvido a partir do inventário e cadastramento de poços tubulares existentes na região, do levantamento e interpretação de dados geológicos e hidrogeológicos, além da coleta e análise de amostras de água de poços tubulares que estão em funcionamento e são utilizados pela companhia de abastecimento CORSAN. Os resultados obtidos permitiram evidenciar que a maioria dos poços apresenta profundidade de até 150 metros com vazões médias que variam de 5 a 20m³ h-1, localizados em zonas de média e alta densidade de fraturas, as quais possuem orientação preferencial para noroeste. Quanto à hidroquímica, as águas que circulam por esses aquíferos são do tipo bicarbonatadas cálcicas ou magnesianas, predominando as águas bicarbonatadas mistas e cálcicas, apresentando pequenas variações quanto à concentração dos íons e suas razões iônicas. Essas características hidroquímicas são típicas de águas que circulam por estruturas de rochas vulcânicas ácidas e indicam um baixo tempo de residência, sendo as concentrações variáveis com as profundidades das entradas da água. This paper presents the hydro-geological and hydro-chemical study of fractured aquifers that form the Serra Geral Aquifer System (SASG) associated with acid volcanic rocks. The study area comprises part of the city of Carlos Barbosa, located in the northeast region of Rio Grande do Sul State. The study was developed based on the inventory and registration of existing wells in the region, the survey and interpretation of geological and hydro-geological data, in addition to the collection and analysis of samples from wells that are in operation and used by the CORSAN water supply company. The results highlighted that most wells have depth up to 150 meters with flow rates average ranging from 5 to 20 m³ h-1, located in areas with medium and high density of fractures, which have preferential orientation to the northwest. As for hydro-chemistry, water circulating through these aquifers is the calcic or magnesium bicarbonate type, predominantly mixed and calcic bicarbonate waters, with minor variations in the concentration of ions and their ionic reasons. These hydro-chemical characteristics are typical of waters that circulate within structures and acid volcanic rocks indicate a low residence, with concentrations varying with water input depths.