Citation Vella et al. 2005

Notre article paru dans Marine Géology :

Evolution of the Rhône delta plain in the Holocene
Vella, C., Fleury, T.-J., Raccasi, G., Provansal, M., Sabatier, F., Bourcier, M.
Marine Geology
volume 222-223, issue 1-4, year 2005, pp. 235 - 265

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	Electrical methods (VES and ERT) for identifying, mapping and monitoring different saline domains in a coastal plain region (Alt Empordà, Northern Spain) Zarroca, M., Bach, J., Linares, R., Pellicer, X.M. Journal of Hydrology volume 409, issue 1-2, year 2011, pp. 407 - 422

Summary

 

The spatial variability through time of the degree of salinity of soils and groundwater is a major issue concerning the sustainable management of water resources. The problem is accentuated in coastal plain areas where saline bodies of different origin coexist.

We present an extensive geoelectrical resistivity dataset collected in the Alt Empordà clastic coastal aquifer system (NE Spain) integrating the results of field campaigns undertaken within a period of more than two decades. The dataset is unique in the literature and comprises highly valuable information for the investigation of saline domains. The joint application of Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT) methods allowed the identification of saline domains and monitoring their evolution through time.

Geophysical data gathered during field campaigns in 1982, 2002 and 2010 were calibrated and interpreted on the basis of soil and groundwater physico-chemical analyses and hydrogeological, stratigraphic and geomorphological data.

The results illustrate the potential of electrical resistivity methods at differentiating saline domains in coastal aquifer areas and at modelling their configuration and evolution. Although the VES data processing allows solving the one-dimensional resistivity structure of the subsurface, the inversion imposes a 1D layered model, thus interpretation of two-dimensional structures is subject to the interpolation between discrete measures. In contrast, ERT data offer a continuous 2D-image of the resistivity distribution, both laterally and in depth. Given that the bulk resistivity of the medium is extremely sensitive to salt content, the ERT profiles permitted identifying and determining the geometry of hyper-saline areas (characterized by resistivities of less than 5 Ω m).

The study demonstrates the efficiency of the electrical methods to map subsurface conductive zones and illustrates how the accurate knowledge of the hydrogeological pattern results critical to meet this objective.

Highlights

► Efficiency of electrical resistivity survey for identifying, mapping and monitoring saline zones. ► Geo-resistivity model based on a multidisciplinary approach and experimental data from lab tests. ► Two surveying campaigns separated by more than 20 years allow characterizing salinity variation.

Keywords: Salinity of soils and water; Vertical Electrical Sounding (VES) surveys; Electrical Resistivity Tomography (ERT); Geophysical mapping; Coastal plain

Article Outline

• 1. Introduction
• 2. Study area
• • 2.1. Geological setting
  • 2.2. Hydrogeology
• 3. Methods
• • 3.1. Soil and groundwater physico-chemical analyses
  • 3.2. Geophysical survey
  • • 3.2.1. Vertical Electrical Sounding (VES)
    • 3.2.2. Electrical Resistivity Tomography (ERT)
• 4. Results and discussion
• • 4.1. Relationship at sample scale between water conductivity, bulk resistivity, nature of sediments and salinity
  • 4.2. Salinity-resistivity of the Alt Empordà coastal plain
  • • 4.2.1. Geoelectrical sections, pseudo-cross-sections 1D and ERT 2D imaging
    • 4.2.2. Apparent resistivity maps
  • 4.3. Time lapse spatial evolution (1982–2002)
• 5. Conclusions
• Acknowledgements
• Appendix A. Supplementary material
• References