Articles | Volume 21, issue 3
Hydrol. Earth Syst. Sci., 21, 1439–1454, 2017
Hydrol. Earth Syst. Sci., 21, 1439–1454, 2017

Research article 09 Mar 2017

Research article | 09 Mar 2017

Flow dynamics in hyper-saline aquifers: hydro-geophysical monitoring and modeling

Klaus Haaken1,a, Gian Piero Deidda2, Giorgio Cassiani3, Rita Deiana4, Mario Putti5, Claudio Paniconi6, Carlotta Scudeler5,6,b, and Andreas Kemna1 Klaus Haaken et al.
  • 1Department of Geophysics, Steinmann Institute, University of Bonn, Meckenheimer Allee 176, 53115 Bonn, Germany
  • 2Dipartimento di Ingegneria Civile, Ambientale e Architettura, Università di Cagliari, Via Marengo 2, 09123 Cagliari, Italy
  • 3Dipartimento di Geoscienze, Università di Padova, Via Gradenigo 6, 35131 Padova, Italy
  • 4Dipartimento di Beni Culturali, Università di Padova, Piazza Capitaniato 7, Palazzo Liviano, 35139 Padova, Italy
  • 5Dipartimento di Matematica, Università di Padova, Via Trieste 63, 35121 Padova, Italy
  • 6Institut national de la recherche scientifique, Centre Eau Terre Environnement, Université du Québec, Rue de la Couronne 490, G1K 9A9 Québec, Canada
  • anow at: Björnsen Consulting Engineers, Maria Trost 3, 56070 Koblenz, Germany
  • bnow at: Risk Management Solutions, Model Development, London, UK

Abstract. Saline–freshwater interaction in porous media is a phenomenon of practical interest particularly for the management of water resources in arid and semi-arid environments, where precious freshwater resources are threatened by seawater intrusion and where storage of freshwater in saline aquifers can be a viable option. Saline–freshwater interactions are controlled by physico-chemical processes that need to be accurately modeled. This in turn requires monitoring of these systems, a non-trivial task for which spatially extensive, high-resolution non-invasive techniques can provide key information. In this paper we present the field monitoring and numerical modeling components of an approach aimed at understanding complex saline–freshwater systems. The approach is applied to a freshwater injection experiment carried out in a hyper-saline aquifer near Cagliari (Sardinia, Italy). The experiment was monitored using time-lapse cross-hole electrical resistivity tomography (ERT). To investigate the flow dynamics, coupled numerical flow and transport modeling of the experiment was carried out using an advanced three-dimensional (3-D) density-driven flow-transport simulator. The simulation results were used to produce synthetic ERT inversion results to be compared against real field ERT results. This exercise demonstrates that the evolution of the freshwater bulb is strongly influenced by the system's (even mild) hydraulic heterogeneities. The example also highlights how the joint use of ERT imaging and gravity-dependent flow and transport modeling give fundamental information for this type of study.

Short summary
The paper presents a general methodology that will help understand how freshwater and saltwater may interact in natural porous media, with a particular view at practical applications such as the storage of freshwater underground in critical areas, e.g., semi-arid zones around the Mediterranean sea. The methodology is applied to a case study in Sardinia and shows how a mix of advanced monitoring and mathematical modeling tremendously advance our understanding of these systems.