Behind The Scenes Of Groundwater Exploration With Electrical Resistivity

Early Methods Of Groundwater Exploration

To best understand how electrical resistivity surveys for groundwater exploration work today, it’s important to understand where resistivity testing began. 

Brothers Conrad and Marcel Schlumberger performed the very first investigation of how electrical current moves through the ground and what you can detect using an electrical resistivity survey in the early 1900s. From their research came what is now one of the most common methods of groundwater exploration, vertical electrical sounding (VES).

An Overview Of The IEEE Standard 81 Fall-Of-Potential Grounding Test

The Institute of Electrical and Electronics Engineers (IEEE) Standard 81-2012 “Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System”, suggests the fall-of-potential grounding test to be used to evaluate the capacity of an electrical grounding system—it is often used by subcontractors to power engineers. 

The 7 Most Common Signs Of Sinkholes & How To Test For Them

One way that sinkholes form is when water in the atmosphere reacts with carbon dioxide and forms a weak carbonic acid. As the slightly acidic rainwater moves through fissures in the limestone, it begins to dissolve and widens the fissures—which eventually creates air or water filled pockets. When those pockets become expansive, they’re called “caves” or “voids.” This is a common natural phenomenon in limestone or dolomite known as karstification—but it can be dangerous, expensive, and life-threatening when the ceiling of a void weakens and caves in. This is known as a “sinkhole.” 

Electrical Resistivity: Everything You Need To Know

At the most basic level, electrical resistivity (ER) (as used in geophysics) is the measurement of ground variations gathered by applying a small and highly controlled electric current across an array of electrodes.

Electrical resistivity imaging (ERI)—also known as electrical resistivity tomography (ERT)—is a geophysical technique used to create an image of a specific portion of the Earth’s subsurface. It is created through the use of automated geophysical instruments that gather thousands of resistivity measurements via an electrode cable and multiple electrodes.

Suggested Reading

Resistivity and IP (Induced Polarization) Inversion Processing

Constable, S., Parker, R.L., and Constable, C.G., 1987, Occam’s inversion: A practical algorithm for generating smooth models from electromagnetic sounding data, Geophysics, 52, 289-300.

DeGroot-Hedlin, D. and Constable, S., 1990, Occam’s inversion to generate smooth, two-dimensional models from magnetotelluric data, Geophysics, 55, 1613-1624.

English

Pages