A Double Scale Methodology to Investigate Flow in Karst Fractured Media via Numerical Analysis: The Cassino Plain Case Study (Central Apennine, Italy)

Abstract

A methodology to evaluate the hydraulic conductivity of the karst media at a regional scale has been proposed, combining pumping tests and the hydrostructural approach, evaluating the hydraulic conductivity of fractured rocks at the block scale. Obtaining hydraulic conductivity values, calibrated at a regional scale, a numerical flow model of the Cassino area has been developed, to validate the methodology and investigate the ambiguity, related to a nonunique hydrogeological conceptual model. The Cassino plain is an intermontane basin with outstanding groundwater resources. The plain is surrounded by karst hydrostructures that feed the Gari Springs and Peccia Springs. Since the 1970s, the study area was the object of detailed investigations with an exceptional density of water-wells and piezometers, representing one of the most important karst study-sites in central-southern Italy. Application of the proposed methodology investigates the hydraulic conductivity tensor at local and regional scales, reawakening geological and hydrogeological issues of a crucial area and tackling the limits of the continuum modelling in karst media.

The geology and hydrogeology of the Cassino plain (central Apennines, Italy): redefining the regional groundwater balance

“…-The observed hydraulic loss along this NW-SE flowpath under the Cassino Plain would be sufficient to hinder significant flow between Gari and Peccia spring, in accordance with Celico (1978Celico ( , 1983 and Lancia et al (2018). Therefore, in terms of water management, Gari and Peccia springs must be considered independent to each other as well as their own recharge areas, respectively Simbruini-Ernici-Cairo Mts.…”

“…Collected data do not highlight the presence of Tortonian sandstone at depth, in accordance with Boni et al (1986). In addition, a doubling of the carbonate sequence cannot be excluded as well as a deep hydrogeological communication between Gari and Peccia springs; however, a numerical flow model from Lancia et al (2018), calibrated to support a groundwater communication between Gari and Peccia springs, does not satisfy the quantitative balance suggested by Boni et al (1986). Therefore, a deep flow communication in the carbonate bedrock is presumable, in accordance with the geological and hydrogeological models of Zalaffi (1964), Accordi et al (1967), Boni et al (1986), and Corda and Brandano (2003), but hydraulic head values are not sufficient to guarantee a significant groundwater flow from Gari towards Peccia springs.…”

“…Corda and Brandano (2003) added new data about the distribution of the Miocene carbonate deposits of the Cassino plain, considering a unique depositional system from a regional point of view, whereas Saroli et al (2014) analyzed the Cassino intermontane basin, evaluating the Quaternary evolution of a restricted sector. Recently, Lancia et al (2018) have performed a numerical model across the Cassino plain to verify the continuity model of Boni et al (1986) from a hydraulic point of view.…”

A macroscale hydrogeological numerical model of the Suio hydrothermal system (central Italy)

“…A c c e p t e d a r t i c l e  Simulation of the fluid flow inside the discrete fractures of the REV and calculation of the equivalent permeability [51];  Assignment of the estimated permeability to the CC complex of the large-scale numerical model in Figure 4. Geomechanical surveys allow analysing the fracturing state of a rock-mass by identifying one or more families of rock joints, constituted by planes parallel to each other, i.e., the joint set.…”

“…The orientation and the spacing of the fractures have been assumed equal to the observed average values, while the aperture has been varied between the observed maximum and minimum values, respectively ( Table 2). The macroscopic equivalent permeability of the REV is then calculated by assuming the simultaneous presence of the bedding and the joint-sets of Table 2 and simulating the flow numerically through the discrete fractures [37], according to the procedure proposed by Lancia et al [51]. The fluid flow inside the fractures obeys to the Darcy law (equations 5 and 6), while the flow through the porous matrix is neglected by assuming an arbitrarily low permeability.…”