Unusual behaviour of epikarst in the Acqua dei Faggi carbonate aquifer (Southern Italy)

Abstract

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.

Bacterial migration through low-permeability fault zones in compartmentalised aquifer systems: a case study in Southern Italy

“…Natural gradient tracer experiments yielded a porosity given by fissures of 2.3 x 10 -4 (Petrella et al, 2008). Lugeon tests indicated limestone hydraulic conductivity on the order of 10 -6 m s -1 (Petrella et al, 2007). The carbonate medium is laterally and vertically well connected in the subsurface, Fig.…”

“…For example, Drogue (1974) shows that the main high-permeability conduits are often developed along fault zones. In contrast, a number of papers (e.g., Celico et al, 2006;Petrella et al, 2007Petrella et al, , 2008Petrella et al, , 2009a) describes a different control of tectonic features on groundwater flow in some carbonate aquifers in Southern Italy. In the latter settings, the aquifer systems can be compartmentalized due to low-permeability fault zones that partially or completely impede groundwater flow (e.g., Celico et al, 2006;Mohamed & Worden, 2006).…”

“…The groundwater responds rapidly to recharge events due to fast and diffuse rainwater infiltration (Petrella et al, 2007). Measurements of the hydraulic head by means of pressure transducers in different wells drilled within the studied aquifer system indicated a time lag of less than a few days between a precipitation cataclastic zones (Chester & Logan, 1987), brecciated and geochemically altered zones (Sibson, 1977), or unconsolidated clay-rich gouge zones (Anderson et al, 1983).…”

“…The epikarst is widely distributed within the study site, with thickness ranging from a few tens of cm to approximately 10 m (Celico et al, 2010). However, the permeability contrast at the base of the epikarst is not large enough to cause water storage in temporary perched aquifers during rainwater infiltration (Petrella et al, 2007). Large karst conduits influence the functioning of the aquifer system locally in terms of groundwater flow and discharge (Petrella et al, 2009a).…”

“…Considering the hydrogeological and isotopic investigations and EC measurements, the results of biomolecular analyses demonstrate that, at the study site, compartments straddling the analyzed fault zones have microbial interconnections, despite the existence of low-permeability fault cores. bacterial communities; carbonate aquifer; groundwater protection; low-permeability fault zone; PCR-DGGE and the fracture spacing is sufficiently dense to allow the application of the continuum approach to describe groundwater flow at the metric scale (Petrella et al, 2007). Darcy's law can be applied in epikarstic horizons with some karstification, and groundwater flow is also expected to be laminar in the fissured bedrock (Petrella et al, 2008).…”