HR: 10:35h
AN: H42B-02    [Abstracts]
TI: Characterization of saltwater intrusion using electrical imaging: numerical simulation and field study
AU: Nguyen, F
EM: f.nguyen@ulg.Ac.Be
AF: Research Center Juelich, Juelich Germany,
AU: Nguyen, F
EM: f.nguyen@ulg.Ac.Be
AF: University of Liege, Liege Belgium,
AU: * Kemna, A
EM: a.kemna@fz-juelich.de
AF: Research Center Juelich, Juelich Germany,
AU: Antonsson, A
EM: arni@geol.ku.dk
AF: University of Copenhagen, Copenhagen Denmark,
AU: Engesgaard, P
EM: PE@geol.ku.dk
AF: University of Copenhagen, Copenhagen Denmark,
AU: Kuras, O
EM: oku@bgs.ac.uk
AF: British geological survey, Nothingham UK,
AU: Ogilvy, R
EM: rdo@bgs.ac.uk
AF: British geological survey, Nothingham UK,
AB: The understanding of subsurface seawater intrusion dynamics is an important requirement for the sustainable management of water resources in coastal areas. Such dynamics is strongly dependent on the given hydrogeological and geochemical conditions and often involves high spatio-temporal variability which may be difficult to characterize using local monitoring wells. In this context, geophysical imaging can help unveiling the dynamics of such systems continuously on a larger scale. In particular electrical imaging has proven to be an efficient non- to minimally invasive tool to characterize subsurface hydrogeological structures as well as to monitor water salinity changes with relatively high spatial resolution. We here investigate the potential of electrical imaging for the characterization of saltwater intrusion in a numerical (two-dimensional) simulation study, where density-dependent flow and transport is modelled for a typical hydrogeological setting. Tomographic acquisition of electrical data is simulated employing surface and borehole electrode arrays, and assuming petrophysical relations between water salinity and electrical conductivity for different lithological units. In a first step, the ability of electrical imaging is studied to reconstruct the spatial electrical conductivity variations associated with both lithology and the salinity distribution corresponding to a steady state scenario for a given set of boundary and initial hydrological conditions. The different investigated scenarios demonstrate the potential of the method for saltwater intrusion characterization, but also show its limitations, for example regarding resolution at depth and for given uncertainty in the underlying petrophysical models or regarding the overlapping effects due to variations in lithology and salinity. Preliminary field results from the site of Almeria, SE Spain, further demonstrates the approach by identifying a saltwater intrusion. Surface and surface to borehole field electrical imaging are compared and highlights inherent limitations of electrical tomography. However, it seems practical that electrical imaging results can be used to constrain seawater intrusion models. This is of importance for improved model predictions for a sustainable management of coastal regions. This work is part of the EU project ALERT (GOCE-CT-2004-505329).
DE: 1835 Hydrogeophysics
DE: 1859 Rocks: physical properties
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Joint Assembly