Skip to main content

The Importance Of Geophysics In Groundwater Investigation



Before we delve into this, we need to first of all define some terms.

What is Geophysics?      It is the use of Physics to solve Geology problems.

What then is Geology?  Simply the study of the Earth. This includes the structure and the rocks.

Geophysics is usually employed when it involves probing the subsurface. In physical Geology, you are dealing with the surface geology, i.e. the structures, forms, and the lithofacies that are visible on the surface.

To solve environmental issues, mining, archeological, engineering (Geotechnical) and geological (hydrogeological) problems, geophysics is employed. It is achieved by passing an electric current via two current electrodes and the potential drop between the two current electrodes is measured by a voltmeter. From this, the resistance is deduced. Here, the current (I) is already known and the potential drop (V) is known as well.
Given the formula:          
V=I×R                                                                           ------- (1)
Making R the Subject:    R=V/I                                    ------- (2) {where R is measured in Ohms}

The essence of carrying out this is to determine the intrinsic properties of the geologic materials present in that environment. What the geophysicist is interested in per see is the Apparent Resistivity. This is usually affected by the presence minerals, groundwater, and porosity.


For groundwater investigation, Electrical Method is used. It involves the introduction of current via wires to the electrodes i.e. Vertical Electrical Sounding (VES). There are two main arrays for this: The Schlumberger array and Wenner array. Although each array has its own limitation, it will help you infer how the subsurface looks like.


There are however some factors that determine the accuracy of your results and are:

  1. The accuracy of the equipment (terrameter) used.
  2. The competency of the geophysicist.
BELOW IS A DISPLAY OF THE ASSEMBLAGE OF THE EQUIPMENT


Fig 1: ASSEMBLAGE OF THE EQUIPMENT(Terrameter) for Geophysical Investigation.


From the readings gotten and interpretation made, the rock-bearing-water is ascertained and the depth of penetration is known.

Comments

Post a Comment

COMMENT

Popular posts from this blog

COMPARISON BETWEEN SCHLUMBERGER ARRAY OVER WENNER ARRAY

COMPARISON   BETWEEN SCHLUMBERGER ARRAY OVER WENNER ARRAY Find below the pros and cons of Schlumberger Array over Wenner Array and vice versa Are you a young geologist? Click HERE NOW!!! Advantages of using Schlumberger Array over Wenner                 It requires less manpower and time than Wenner soundings.                 It is less sensitive to lateral variations in resistivity. The potential electrodes are moved only occasionally; In a Wenner sounding the potential and the current electrodes are always moved after each measurement. It is faster in field operation. Types of VES Curves Requires less physical movement of electrodes than the normal Wenner array because only the current electrodes must be moved between readings. The effects of near surface, lateral inhomoge...
2 comments
Read more

Vasquez Rocks

Have you heard of Vasquez Rock? Credit: The above picture will be alien except to those within the vicinity of Aqua Dulce, California or perhaps, those that have visited here at one time or the other. Just watch the arcs and the angles formed by this deposit!! In case you do not know, the image you are seeing is Vasquez Rocks. Am fascinated about the arcs and the acute angles formed by this deposit.. Your groundwater may be polluted!!! Nature is indeed wonderful!!!! For emphasis sake, this is in Aqua Dulce, California, north of Los Angeles. Research has it that the ‘arcs’ formed (i.e. tilting was as a result of the North American Plate collision with the Pacific Plate) along the San Andreas fault. We can see that the collision resulted in the uplift.
2 comments
Read more

Principles and limitations geophysical method of exploration

Geophysics simply means the application of principles of physics in the study of the earth. The application of geophysics is vast. It can be used to study the entire Earth (Global geophysics), or for localized survey of the crust e.g for Engineering purposes. Geophysical survey is broadly classified into two based on the source of energy. 1.        Natural field: This uses the electric, magnetic,  electromagnetic and gravitational fields of the Earth 2.        Artificial source: Involves the generation of artificial electrical or electromagnetic fields into the earth by a means of a D.C. Magnetic method is applied when searching for buried magnetite ores because of their high magnetic susceptibility. Electrical method is used when exploring for ground water because rocks resistances differ according to their water saturation levels. Seismic method is used for hydrocarbon exploration. It is worth noti...
2 comments
Read more