Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

Abstract

Low-frequency geoelectrical methods include mainly self-potential, resistivity, and induced polarization techniques, which have potential in many environmental and hydrogeological applications. They provide complementary information to each other and to in-situ measurements. The self-potential method is a passive measurement of the electrical response associated with the in-situ generation of electrical current due to the flow of pore water in porous media, a salinity gradient, and/or the concentration of redoxactive species. Under some conditions, this method can be used to visualize groundwater flow, to determine permeability, and to detect preferential flow paths. Electrical resistivity is dependent on the water content, the temperature, the salinity of the pore water, and the clay content and mineralogy. Time-lapse resistivity can be used to assess the permeability and dispersivity distributions and to monitor contaminant plumes. Induced polarization characterizes the ability of rocks to reversibly store electrical energy. It can be used to image permeability and to monitor chemistry of the pore water-minerals interface. These geophysical methods, reviewed in this paper, should always be used in concert with additional in-situ measurements (e.g. in-situ pumping tests, chemical measurements of the pore water), for instance through joint inversion schemes, which is an area of fertile on-going research.

Quantifying shallow subsurface water and heat dynamics using coupled hydrological-thermal-geophysical inversion

“…The bulk electrical conductivity (σ b ) includes contributions from the electrical conductivity of pore water and the surface conduction at the pore and water-mineral interface (Revil et al, 2012). We employed the model proposed by Linde et al (2006), which was extended from Archie's model (Archie, 1942), and is expressed below as…”

Using the Resistivity Imaging Method to Monitor the Dynamic Effects on the Vadose Zone During Pumping Tests at the Pengtsuo Site in Pingtung, Taiwan

“…The average of the inversion RMS (root mean square) is about 19.3%, which is due chiefly to the field noises from pumping activities and using the 2D inversion scheme for the 3D objects. Factors that can generate noisy measurements in pumping environments include induction in the ground associated with power lines, direct current injection associated with cathodic grounding (Corwin and Hoover 1979), and the metallic casing of a piezometer (Revil et al 2012). These factors are the possible sources that contribute to noisy measurements and higher RMS in the inversion.…”

Geophysical Methods for Monitoring Temperature Changes in Shallow Low Enthalpy Geothermal Systems

“…Electrical resistivity tomography (ERT) has proven its efficiency to image and/or monitor spatial phenomena [43] such as salt water intrusions [44,45], variations in moisture content (e.g., [46,47]), biodegradation of hydrocarbons (e.g., [48,49]) and salt tracer experiments (e.g., [50,51] and references therein). An in-depth review of electrical properties of rocks can be found in Schön [52] or Revil et al [53], whereas a description of electrical methods can be found in Binley and Kemna [54]. The panel seems slightly heterogeneous and reflects lithological changes.…”