Complex flow circulation patterns are likely to be present in fault‐controlled groundwater flow systems, such as carbonate aquifers. Nevertheless, not much information is available for faults in carbonates, and their hydrogeological behaviour is often neglected in conceptual and numerical models. The understanding of this aspect of subsurface fluid flow has been improved in a carbonate aquifer, where hydrogeological investigations at site scale demonstrated the existence of fault zones that act as barriers. The hydraulic conductivity of the fault core is as low as that of siliciclastic rocks that represent the regional aquitard of the carbonate aquifer. Despite the lower permeability, the fault zones allow a significant groundwater flowthrough and a good interdependence of piezometric heads upgradient and downgradient of the faults. Because of this discontinuous heterogeneity, the aquifer looks like a basins‐in‐series system, where seasonal springs can be detected along some fault zones, as a function of groundwater level fluctuations.

Epikarst formation in the southern Apennines (Italy) was hypothesized to be significantly influenced by diffuse rainwater infiltration through soil of pyroclastic origin. Multidisciplinary investigations were carried out at an experimental field site to test this hypothesis. At this site, other factors influencing epikarst formation can be assumed invariant. A direct relationship was observed between soil thickness and epikarst thickness. This relationship supports the hypothesis that the pyroclastic soil plays a significant role in governing epikarst evolution and thickening. The sandy loam texture and the high hydraulic conductivity of the soil allow easy rainwater infiltration, therefore causing a diffuse interaction between percolation water and the soil medium, and spatially homogeneous recharge within the aquifer system. The soil contains a large accumulation of organic carbon and considerable CO2 production results from the activity of autochthonous microorganisms belonging to different genera

Abstract:The Ischia hydrothermal system was analysed through hydrogeological and microbial community investigations. Mesophilic communities were detected in two cold springs, suggesting a negligible influence of thermal circuits in freshwater sub-systems which are mainly or only fed by local precipitations. Thermophilic and extremely thermophilic bacteria were detected in two wells, according to higher water temperatures (61 and 85°C), even if the two communities show significant differences. In one well, thermophilic and extremely thermophilic bacteria are associated with strains belonging to ε-Proteobacteria isolated in different sulphur-rich carbonate environments. This association suggests a greater influence on ascending hot fluids that interact with the carbonate basement of volcanic rocks. In the other well, thermophilic and extremely thermophilic bacteria are associated with strains isolated in cold hypersaline environments or in aquatic habitats where terrestrial and marine components are coupled. This association supports the fact that seawater intrusion can affect this part of Ischia, according to results of hydrogeological and geochemical surveys. Differences in groundwater temperature and bacterial communities are probably mainly due to differences in permeability between volcanic rocks and differences in hydrogeologic behaviour between faults in the upper carbonate basement, above the deep magma chamber, that influence relationships between ascending hot fluids and local recharge. This study contributes to discussion of the reliability of the actual behaviour models of the Ischia system, based on the results of geochemical and isotopic investigations, and, in a wider context, it shows that microbial community investigations may be a valuable supplementary tool for analysing hydrothermal system behaviour.

This paper summarizes the results of a study focused on the hydrogeological characterization and recognition of groundwater resources in continental southern Italy, developed under the European INTERREG IIC Programme. The study reconstructed up-to-date scientific knowledge regarding aquifers, groundwater circulation schemes and groundwater resources exploitation in the administrative regions of southern Italy included in the Objective I (Molise, Campania, Basilicata, Puglia and Calabria). In this paper, the methodological approaches applied to synthesize and homogenize bibliographic data collected from the hydrogeological literature and to set a regional hydrogeological mapping are described. Results presented are three hydrogeological maps, 1:300,000 scale, showing hydrogeological units and groundwater flow schemes that are relevant in the regional hydrogeological context, and a brief description of principal types of aquifer and groundwater resources of continental southern Italy. ARTICLE HISTORY

Abstract:The sedimentary sequences containing lithologic units with low permeability represent hydrogeologic systems which, as of now, have been little studied despite their diffusion worldwide. A hydrogeologic study, aimed to assess the main factors controlling the groundwater flow dynamics in such systems and their hydraulic interactions with nearby carbonate aquifers, has been carried out in Longano (Isernia, Southern Italy).The analysis of the hydraulic heads, combined with the regimes of the springs and the electric conductivity of the groundwater, mainly reflect vertical and lateral heterogeneities of the media in terms of hydraulic properties. In particular, the flow system is controlled by lateral heterogeneities, which characterize a surficial horizon made up of clayey colluviums and talus deposits, separated from the deeper saturated, fissured bedrock. One-to-ten relationships in hydraulic heads, monitored in piezometers crossing the fissured media, further uphold the crucial role played by the lateral contrasts of permeability in controlling the flow dynamics. On the whole, significant interactions with the nearby carbonate hydrostructure take place. Nevertheless, the heterogeneities of the siliciclastic succession and surficial horizon, coupled with the compartmentalization of the carbonate system, leads to a complex hydrogeological scenario.In a wider perspective, this study gives information of utmost importance in order to improve the implementation of mathematical models and configuration of tapping works within these heterogeneous and complex settings.