Estimation of hydraulic conductivity and water table map in a large‐scale laboratory model by means of the self‐potential method

Abstract

[1] The goal of this paper is to estimate the position of the water table and hydraulic conductivity of a homogeneous porous medium by means of the self-potential method. The hydrogeophysical experiments were carried out at the Hydrogeosite Laboratory of the Istituto di Metodologie per l'Analisi Ambientale, Consiglio Nazionale delle Ricerche (Marsico Nuovo, Italy); the laboratory is a large-scale model sized 10 × 7 × 3 m 3 that is filled with a homogeneous medium made up of quartz-rich sand with a medium-high hydraulic conductivity in the order of 10 −5 m s −1 . Self-potential signals generated by the groundwater flow, during a pumping test, were measured on the ground surface, on both the pumping and the recovery phases. A novel methodology to estimate the hydraulic conductivity from self-potential measurements is proposed. Hydraulic conductivity very close to that calculated from hydraulic data, by means of Neuman-type curves, has been obtained by solving the electrical flow equation through a linear least squares method. Moreover, a kriging with external drift geostatistical methodology has been proposed to estimate the hydraulic head distribution. The advantages given by this geostatistical method are that (1) hydraulic head distribution can be estimated without any previous electrokinetic coupling coefficient calculation and (2) the method is valid for either linear or nonlinear relationships between self-potential and hydraulic head gradients. An original finding of this work is that the relationship between self-potential signals and drawdown, around a pumping well, is not always linear: linearity applies only when the groundwater velocity is low, but high nonlinearity occurs when hydraulic head gradient rises up. Kriging with the external drift method could be used for the inversion of the hydraulic conductivity distribution, in a real heterogeneous aquifer, by means of an appropriate conditioning technique.Citation: Straface, S., E. Rizzo, and F. Chidichimo (2010), Estimation of hydraulic conductivity and water table map in a largescale laboratory model by means of the self-potential method,

Hydraulic conductivity field characterization from the joint inversion of hydraulic heads and self‐potential data

“…Note that the self-potential data that need to be considered in the inversion are the difference between the values measured prior the pumping tests and the values in steady state condition of flow. This point has been discussed in several papers, for instance, Rizzo et al [2004], Suski et al [2006], and Straface et al [2010].…”

“…[] and Straface et al . [] but these works ignored the complications associated with the flow in the vadose zone. Recent modeling of the streaming current generated in unsaturated media [ Linde et al ., ; Vinogradov and Jackson , ; Jougnot et al ., ; Revil and Mahardika , ] makes it possible to simulate the effect of flow in the vadose zone under transient conditions.…”

“…A general theory of the streaming current in poroelastic and unsaturated porous rocks and soils can be found in Revil and Mahardika []. Due to its sensitivity to the water motion in the porous medium, the self‐potential method has been used to monitor hydraulic head changes associated with pumping tests [for instance, Semenov , ; Rizzo et al ., ; Titov et al ., ; Maineult et al ., ; Jardani et al ., ; Straface et al ., ]. These works have been mostly focused on showing the existence of recordable signals, in performing forward modeling of the self‐potential response, and in developing simple interpretation schemes, mostly based on the linear relationship between the changes in the self‐potential signals and the concomitant changes in hydraulic heads.…”

The self potential method

“…Mapping SP near the radial arms of a collector well can help demarcate the effective part of the radial arms in capturing groundwater (Muralidharan et al, 2005). SP profiles provide information on variations in depth to water table in an area (Birch, 1998;Suski et al, 2006;Jardini et al, 2009) and can be used to estimate hydraulic conductivity also (Straface et al, 2010). Fagerlund and Heinson (2003) carried out SP surveys during pumping tests and indicate the possibility of obtaining hydrogeological parameters.…”

Theory of transient streaming potentials in coupled unconfined aquifer‐unsaturated zone flow to a well

“…[], Straface et al . [], and Malama []. In this work, we follow this pattern of laboratory experiments.…”