### 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.

### CAUSES OF WATER BOREHOLE FAILURES IN NIGERIA

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 stored and harvested when needed. The hole can be shallow (as in wells), o…

### GROUNDWATER POLLUTION (vis-à-vis Groundwater Quality) AND CAUSES

Groundwater in it’s natural state is made up of dissolved substances including gases. These contribute greatly to it’s quality. The surrounding environment (Formations), anthropological and bacterial activities influence it’s quality as well.

Below is a rundown of factors that determine the quality of any groundwater:

They can be categorised into:
1.Physical factors;
2.Bacterial factors;
3.Chemical factors;
4.Anthropological factors.

Physical factors can be easily seen with the eyes without first being analysed in the laboratory. They are apparent to the physical senses of sight, smell, taste and in some cases, touch. It can be known physically if a groundwater is polluted or not by Colour changes, Odour, presence of suspended materials. The presence of suspended materials make the water appear cloudy. Commonsensically, no sane person will like to consume anything, let alone, water that is not appealing to the eyes.

Chemical pollutants are determined by the mineral composition of the underly…