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

THE AGE OF THE EARTH - THE OLDEST MAN ON EARTH IS THE EARTH

THE AGE OF THE EARTH Hey … Just as we celebrate our birthdays to commemorate the day we were born, has it ever occurred to you to ponder on the age of the earth? Don’t you think that there was a day (way back) when the earth was formed? Don’t get it twisted!!! This is no myth. It is a reality. It is REAL!!! The Earth is approximately 4.6 billion years old!!! Sounds absurd??? Well, this figure did not come as a result of fiction or imagination – but by radiometric dating in the early 20 th century. Lead in uranium-rich minerals when dated by early scientists,  were able to discover that they were billions of years old. Another pointer to this is that small crystals of Zircon obtained from Jack Hills, Western Australia when dated, was around 4.4 billion years old. One may ask: “How is this possible”? Rocks are aggregate of minerals. Some of these minerals have radioactive elements like Uranium and Thorium. In the process of their decay (radioac...
11 comments
Read more

CAUSES OF WATER BOREHOLE FAILURES IN NIGERIA

HAVE YOU HEARD ABOUT OIL SHALES BEFORE?? Water is one of the most (if not the most) essential requirements for life existence on earth. It is a well known fact that the human body is made up of about 75% water. Apart from water for drinking, it is relied on for industrial and domestic chores. It is available in the surface and sub-surface. But the surface water is usually not enough and in most cases not available all year round due to seasonal variations namely: Rainy and Dry Seasons . During the Rainy Season, the Surface water becomes readily available (though may or may not be enough depending on the need) but the contrast is the case during Dry Season. Hence the resort to Boreholes . Let’s start by defining a Borehole. In the simplest term, as the name implies: Bore Hole.  It means to ‘ bore a hole’ ; or simply put: ‘to drill a hole’, ‘to sink a hole’, ‘to punch a hole’ on the ground to create a cavity inside the ground where water can accumulate, be sto...
Post a Comment
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