Determination of the permeability of seepage flow paths in dams from self-potential measurements

Abstract

The flow of the pore water in porous media generates an electrical current known as the streaming current. This current is due to the drag of the excess of charge contained in the electrical diffuse layer coating the surface of the grains. This current is associated with an electric field called the streaming potential field. The fluctuations of this field can be remotely measured using a set of non-polarizable electrodes located at the ground surface or in wells and a sensitive voltmeter. The self-potential method (SP) aims at passively measuring the streaming potential anomalies associated with ground water flow. We present a stochastic numerical framework for inverting self-potential data in order to localize seepages in dams and characterize their permeability and Darcy velocity. Our approach is based on the use of Markov chains Monte Carlo (McMC) method for solving the inverse problem. We performed first a validation of the method on a synthetic case study and then on large-scale field surveys on three different dams. Our approach is successful in localizing seepages and determining their permeability. A sensitivity study is performed on each of these three dams to better define the hydraulic and electrical parameters influencing the self-potential signal and the uncertainties associated with the estimation of those parameters. Our results show that the self-potential method can provide quantitative hydrogeological information for the characterization of seepages in dams and dikes.

A monitoring system for spatiotemporal electrical self-potential measurements in cryospheric environments

“…Finally, the streaming potentials need to be analyzed with regard to not only time but also space, given the large surface and subsurface heterogeneities in mountainous areas. Here, methods ranging from simple to advanced could be used, correlating the orientation of specific dipoles to water flow (simple) or applying advanced tomographic algorithms to pro-duce 3D subsurface water flow patterns from measured SP signals (e.g., Jardani et al, 2007;Ahmed et al, 2013Ahmed et al, , 2020. Any inversion of the data would also enable further analysis with regard to a successful extraction of process signatures.…”

“…Fluid flow in porous media generates electrical potential gradients, so-called streaming potentials, commonly antiparallel to the fluid pressure gradient (e.g., Telford et al, 1990;Bernabé, 1998;Revil et al, 2012). The electrical charge separation, required to build up these potentials, happens at the shear plane of the so-called electrical double layer (EDL), which is a multilayered ion concentration gradient structure that forms at the interface of charged surfaces and bipolar liquids (e.g., Revil et al, 2012).…”

“…The HS equation was initially developed only for capillary flow but was later shown to also work for porous media with arbitrary pore space geometry, as long as the surface conductivity of the subsurface is small compared to the fluid conductivity (e.g., Morgan et al, 1989;Bernabé, 1998;Jougnot et al, 2019). In order to formulate the problem for a spatially variable flow (and thus electrical potential) field, a formulation based on transport equations for representative volumes of electrical and fluid flow is used (e.g., Jardani et al, 2007;Jougnot et al, 2020, and references therein).…”

“…Passive SP signatures have been used to assess a multitude of different research questions, such as the long-term investigation of unsaturated water flow in lysimeters (e.g., Doussan et al, 2002), characterizing pumping experiments (e.g., DesRoches and Butler, 2016;DesRoches et al, 2018, and references therein), assessing earthquake triggers (e.g., Bernabé, 1998;Guzmán-Vargas et al, 2009, and references therein), characterizing dams (e.g., Moore et al, 2011), and monitoring volcanoes (e.g., Maio et al, 1997;Friedel et al, 2004). Water flow in and around trees has also been investigated in some long-term experiments using the SP method (e.g., Gibert et al, 2006;Voytek et al, 2019).…”

Induced polarization as a tool to characterize shallow landslides

“…They have been applied to landslides and earthflows by various researchers (e.g., Schmutz et al, 2000Schmutz et al, , 2009Hibert et al, 2012;Malehmir et al, 2013). In the realm of hydrogeophysics, self-potential and induced polarization are two geophysical methods offering useful information to characterize ground water flow (e.g., Soueid Ahmed et al, 2020a), water and clay contents (Soueid Ahmed et al, 2020b), and permeability (Titov et al, 2010;Revil and Florsch, 2010;Soueid Ahmed et al, 2014;Weller et al, 2015), all essential ingredients to better understand and prevent landslides. Induced polarization refers to the study of both conductivity and low-frequency polarization properties of rocks.…”