A Multi-Scale Approach in Hydraulic Characterization of a Metamorphic Aquifer: What Can Be Inferred about the Groundwater Abstraction Possibilities

Abstract

Hard-rock aquifers, which constitute a water supply source in many countries, are highly heterogeneous and defining a realistic model of an aquifer can be extremely complex. The objective of this study was to hydraulically characterize a metamorphic aquifer in a representative area of Italy and to identify the most appropriate approach for tapping of groundwater in this challenging environment. The results of surface fracture surveys, injection tests, pumping tests, and a simplified numerical model were compared. From the surface fracture survey, a model of the rock mass characterized by a well-developed discontinuity network and by a high frequency of discontinuities resulted. The injection tests showed the extreme heterogeneity and the lower hydraulic conductivity of the rock mass in comparison with the results of the pumping tests. The independent estimate of the hydraulic parameter resulting from numerical model highlighted a range of values higher than those resulting from the pumping tests. The study demonstrated that the continuum medium approach can be used in the case of hard-rock aquifers with a dense network of discontinuities. The multi-scale approach is recommended for investigating hydraulic heterogeneity and significantly helps to identify the most promising areas for well locations and their characteristics in relation to the style of fracturing. OPEN ACCESSWater 2015, 7 4639

Occurrence and flow of groundwater in crystalline rocks of Sardinia and Calabria (Italy): an overview of current knowledge

“…Several tens of wells drilled in the fissured layer Special Issue AQUA2015 -DOI: 10.7343/as-2016-195 of granitoid rocks (and in some cases also including their weathered mantle) show yields between 0.1 and 2 L/s, values of transmissivity between 10 -6 and 10 -4 m 2 /s and of storativity between 0.05 and 2 % (Barrocu 2003;2007). In Southern Sardinia, some wells drilled near a faulted zone in the fissured layer of low-grade metamorphic rocks show yields between 1 and 3 L/s, values of transmissivity between 10 -4 and 10 -3 m 2 /s and of storativity between 0.03 and 3 % (Baiocchi et al 2015). At present, only about thirty springs (Fig.…”

“…Current knowledge on the hydrogeology of the crystalline rocks of Sardinia and Calabria is scarce. General considerations on occurrence of groundwater flow and some studies limited to specific areas are reported in the scientific and technical literature (e.g., Celico et al 2000;Barrocu 2003;Allocca et al 2006;Regione Autonoma della Sardegna 2006a;2006b;Barrocu 2007;Regione Calabria 2008;Baiocchi et al 2014;Baiocchi et al 2015).…”

Technical Report Evaluation and study of radon occupational exposure levels in dams: a case study of the Gallery of Medau Zirimilis Dam (Sardinia, Italy)

“…1, the dam is located at the transition area where the Paleozoic basement is related to the Hercynian orogenic evolution outcrops. The Paleozoic basement consists of an originally sedimentary succession (Lower Cambrian to Early Carboniferous) that was deformed during the Carboniferous period under the low metamorphic to anchizonal setting (20,21). The Arburese Unit outcropping at the dam site consists of the Arenarie di San Vito Formation (Middle Cambrian to Lower Fig.…”

“…Ordovician), which is several hundred metres thick and is composed of decametric to metric alternations between micaceous metasandstones, quartzites and metasiltstones. Clastic, poorly cemented sediments, from gravels to sands and silts, of the Upper Pleistocene to the Holocene overlay the metamorphic basement (21).…”

“…The Hercynian tectonics favoured the thrust of the Arburese Unit over the Upper Ordovician to Lower Carboniferous succession and its deformation in large-scale folding with axes of folds E-W and N-S oriented. The Pliocene tectonics shallowly modified the structural setting through normal fault systems E-W and N-S to NNW-SSE oriented (20)(21)(22). In the case of hydrogeological properties of the Paleozoic basement, it is known that the metamorphic rocks form a low-permeability aquifer where groundwater circulation occurs in the fissured zones close to the surface (on average, the first tens of metres).…”