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.

Hydrogeological and geophysical investigations demonstrated the existence of an epikarstic zone in a carbonate aquifer of Southern Italy, about 10 m thick. Nevertheless, the hydrogeological behaviour of the epikarst is different from that schematized by several authors. In the test site, the contrast in permeability at the bottom of the epikarst does not cause retention of percolation and storage of water in a perched temporary aquifer within the uppermost portion of the carbonate medium. Because of the high fracture density and good interconnection of openings within the underlying limestone, the percolation is diffuse also below the epikarstic zone, as well as the groundwater flow. The ‘funnelling’ effect into larger shafts does not play an important role on the hydrogeological behaviour of the aquifer.

Springs are biodiversity hotspots and unique habitats that are threatened, especially by water overdraft. Here we review knowledge on ambient-temperature (non-geothermal) freshwater springs that achieve sufficient oversaturation for CaCO3 -by physical CO2 degassing and activity of photoautotrophs- to deposit limestone, locally resulting in scenic carbonate structures: Limestone-Precipitating Springs (LPS). The most characteristic organisms in these springs are those that contribute to carbonate precipitation, e.g.: the mosses Palustriella and Eucladium, the crenophilous desmid Oocardium stratum, and cyanobacteria (e.g., Rivularia). These organisms appear to be sensitive to phosphorus pollution. Invertebrate diversity is modest, and highest in pools with an aquatic-terrestrial interface. Internationally, comprehensive legislation for spring protection is still relatively scarce. Where available, it covers all spring types. The situation in Europe is peculiar: the only widespread spring type included in the EU Habitat Directive is LPS, mainly because of landscape aesthetics. To support LPS inventorying and management to meet conservation-legislation requirements we developed a general conceptual model to predict where LPS are more likely to occur. The model is based on the pre-requisites for LPS: an aquifer lithology that enables build-up of high bicarbonate and Ca(2+) to sustain CaCO3 oversaturation after spring emergence, combined with intense groundwater percolation especially along structural discontinuities (e.g., fault zones, joints, schistosity), and a proper hydrogeological structure of the discharging area. We validated this model by means of the LPS information system for the Emilia-Romagna Region (northern Italy). The main threats to LPS are water diversion, nutrient enrichment, and lack of awareness by non-specialized persons and administrators. We discuss an emblematic case study to provide management suggestions. The present review is devoted to LPS but the output of intense ecological research in Central Europe during the past decades has clearly shown that effective conservation legislation should be urgently extended to comprise all types of spring habitats.

Limestone aquifers provide the main drinking water resources of southern Italy. The groundwater is often contaminated by fecal bacteria because of the interaction between rocks having high permeability and microbial pollutants introduced into the environment by grazing and/or manure spreading. The microbial contamination of springwater in picnic areas located in high mountains can cause gastrointestinal illness. This study was carried out in order to analyze the interaction between Enterococcus faecalis and the soil of a limestone aquifer and to verify the influence of this interaction on the time dependence of groundwater contamination. E. faecalis was chosen because, in the study area involved, it represents a better indicator than Escherichia coli. The research was carried out through field (springwater monitoring) and laboratory experiments (column tests with intact soil blocks). The transport of bacterial cells through soil samples was analyzed by simulating an infiltration event that was monitored in the study area. Comparison of laboratory results with data acquired in the field showed that discontinuous precipitation caused an intermittent migration of microorganisms through the soil and produced, together with dispersion in the fractured medium (unsaturated and saturated zones), an articulated breakthrough at the spring. The short distances of bacterial transport in the study area produced a significant daily variability of bacterial contamination at the field scale.

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