ABSTRACT
Geo-electrical survey using
Vertical Electrical Sounding (VES) was carried out in the Sports Complex of Federal
University of Petroleum Resources, Effurun Delta State (FUPRE) in order to
determine the groundwater potential of the area and the aquifer distribution.
The Schlumberger electrode configuration was used with a maximum current
electrode separation of 120m. A total of three (3) VES points were used where
at VES1we had 23 measurements, 14 at VES2 and 22 at VES3. The data were
analysed by computer aided iteration techniques using the resistivity modelling
software (IPI2Win+IP). The geo-electric model parameters and curves were
obtained from the software. The result of the analysis shows six geo-electric
layers. The result of the survey has allowed the delineation of ground water
potential in the study area and it is recommended sinking of a reliable borehole
for good portable water be sited at locations VES1 and VES3 at recommended
drill depth of 40.8m respectively.
TABLE OF CONTENT
Certification……………………………………………………………………………...i
Dedication……………………………………………………………………………….ii
Acknowledgements……………………………………………………………………..iii
Abstract………………………………………………………………………………….iv
Table of Content…………………………………………………………………………v
List of Figure…………………………………………………………………………...vii
List of Tables…………………………………………………………………………..viii
Chapter
One…………………………………………………………………………...…1
1.1 Background
of Study……………………………………………………...……....1
1.2 Statement
of Problem………………………………………………………...…...3
1.2.1 Basic Terms in
Groundwater Study………………………………………..3
1.3 Aim and
Objective of Study…..……………………………………...…..……….6
1.4 Significant
of Study…………………………………………………………….....7
1.5 Scope of
Study……………………………………………………………………7
Chapter
Two………………………………………….……………………………..…..8
2.1 Literature
Review……………………………….………………………………..8
2.1.1 Local
Geology……………………………………………………………..8
2.1.2 Local Hydrogeology……………………………………………………….8
2.1.3 Regional
Hydrogeology……………………………………………………8
2.1.4 Regional
Geology…………………………………………………….……9
2.1.5 Description of Study
Area………………………………………………...10
2.2 Theoretical/Conceptual
Framework……………..…………………………12
2.3 Review of Previous
Work………………………………………………….13
Chapter
Three……………….……………………………………………………….....14
3.1 Methods………………………………………………………………………….14
3.1.1 Vertical Electrical
Sounding (VES)……………………………………....15
3.1.2 Schlumberger Array
Configuration……………………………………....15
3.2 Nature of
Data…………………………………….……………………………..17
3.2.1 Instrumentation…………………………………………………………...18
3.3 Method of
Analysis……………………………………………..……………….20
Chapter
Four……………………………………………………………….……….......22
4.1 Data
Analysis….………………………………………………….………..........22
4.2 Interpretation…………………………………………………………...............26
4.3 Discussion of
Result……………………………………………………………..31
Chapter
Five……………………………………………………………………………32
5.1 Conclusion……………………………………………………………………….32
5.2 Recommendation………………………………………………………………..32
5.3 Contribution to
Knowledge……………………………………………………...32
References……………………………………………………………………………...33
LIST OF FIGURES
Fig.1.1:
Schematic Cross-sections of Aquifer Types (Modified after Hartan et al, 1989)….5
Fig.2.1: Map
of Effurun-Warri Metropolitan Area (Odemerho, 1986)………………...11
Fig.2.2:
FUPRE Base Map……………………………………………………………..11
Fig.3.1:
Geometric arrangement of the Schlumberger array configuration……………16
Fig 3.2:
Instruments Set-up (Cables, Ranging Poles and Ohmega Terrameter)………..19
Fig. 3.3:
GPS, Hammer, Cutlass………………………………………………………..19
Fig.3.4:
Measuring Tape………………………………………………………………..19
Fig.3.5:
Electrodes……………………………………………………………………...19
Fig.3.6:
Curve Types…………………………………………………………………...21
Fig.4.1:
Curve Type of VES1…………………………………………...……………...27
Fig.4.2:
Curve Type of VES2…...……………………..……………………………….27
Fig.4.3:
curve type of VES3……………………………………………………..…......28
Fig.4.4:
pseudo cross section merging VES1 and VES2…………………………….....28
Fig.4.5:
pseudo cross section merging VES2 and VES3…………………………….....29
Fig.4.6:
pseudo cross section merging VES3and VES1………………………………..29
LIST OF TABLES
Table 4.1:
Schlumberger Data for VES1…………………………………………….…23
Table4.2:
Schlumberger Data for VES2………………………………………………..24
Table4.3:
Schlumberger Data for VES3………………………………………………..25
Table4.4:
Summary of iteration result and Lithology of the Area……………………..30
CHAPTER
ONE
1.0 INTRODUCTION
1.1 BACKGROUND
OF STUDY
Hidden beneath the varied landscapes of the Niger Delta is a treasured
and important natural resource. It is neither petroleum nor natural gas, which
are the natural resources that are certainly important and have brought wealth
to many people. This hidden treasure is water, and to be more specific,
groundwater. Groundwater occurs everywhere but sometimes its availability in
economic quantity depends solely on the distribution of the subsurface geologic
units that are referred to as the aquifers. This implies that where groundwater
is not potentially endowed enough, there may be either complete lack or
inadequacy due to increasing industrial and domestic needs (Akpan, 2006 and
George, 2010). Although groundwater is a renewable resource, fear is being
nursed about its imagined danger in case of inadequacy or lack. The
universality of its utility heightens the degree of fear as no other fluid can
replace the uncountable roles played by water in our communities. However, when
many people think of a water source, they think of lakes, rivers and streams;
in other words, surface water. Of all the usable freshwater in the world,
approximately 97 percent of it is groundwater. According to the United Nations,
10 million cubic kilometres of water are stored underground. The United States
Geological Survey states that there is about 4.2 million cubic kilometres of
water within 0.8 kilometre of the earth’s surface.
Groundwater
is the water that lies beneath the ground surface, filling the pore space
between grains in bodies of sediment and elastic sedimentary rocks and filling
cracks and cavity in all types of rocks (Plummer et al, 1999). Observations
have shown that a good deal of surplus rainfall runs-off over the surface of
the ground while the other part of it infiltrates underground and becomes the
groundwater responsible for the springs, lakes and wells (Oseji et al., 2006).
Groundwater is often withdrawn for agricultural, municipal and industrial use
by constructing and operating extraction wells. Groundwater is also widely used
as a source for drinking supply and irrigation (UNESCO, 2004). Although
groundwater cannot be seen above the earth, a scope of techniques can be used
in determining its availability in the subsurface. Surface investigation allows
us in deciding the information about type, porosity, water content and density
of subsurface condition. This is usually done with the help of electrical and
seismic methods and without any drilling on the ground. The data supplied by
these techniques are partly reliable and it is less expensive. It gives only
indirect signs of groundwater so that the underground hydrologic record must be
inferred from the subsurface investigations. Of all the surface geophysical
methods, electrical resistivity has been employed most for groundwater
exploration (Egbai, 2011). This is because the equipment is portable, simple,
field logistics are easy and straightforward and the analysis of data is
economical and less tedious than other methods (Zhody et al, 1993; Egbai,
2011).
As time goes on the demand for
water for various purposes will be increasing day by day due to increasing
population within Federal University of Petroleum Resources Effurun.
This work is aimed at delineating
the depth to groundwater using Vertical Electrical Sounding (VES) with the
Schlumberger electrode configuration in the Sports Complex of FUPRE to be able
to infer suitable locations where prolific boreholes can be sited.
1.2 STATEMENT
OF PROBLEM
Here this study focuses mainly on
the delineating of good groundwater aquifer in the Sports Complex of FUPRE and
how it can be evaluated using resistivity method. But first I will like to
discuss briefly about the basic terms in groundwater study.
1.2.1 BASIC TERMS IN GROUNDWATER STUDY.
AQUIFER: An aquifer is a ground-water reservoir composed of
geologic units that are saturated with water and sufficiently permeable to
yield water in a usable quantity to wells and springs. Sand and gravel
deposits, sandstone, limestone, and fractured crystalline rocks are examples of
geological units that form aquifers. Aquifers provide two important
functions:
(1) They transmit ground water from areas
of recharge to areas of discharge.
(2) They provide a storage medium for useable
quantities of groundwater.
The amount of water a material can hold depends upon its porosity. The
size and degree of interconnection of pore spaces (permeability) determine the
materials’ ability to transmit fluid.
UNCONFINED AQUIFERS: An unconfined aquifer is one in which a water
table varies in undulating form and in slope, depending on areas of recharge
and discharge, pump rate from wells, and permeability. Rises and falls in the
water table correspond to changes in the volume of water in storage within an
aquifer.
Fig.1.1 shows an idealized section
through an unconfined aquifer; the upper aquifer is also unconfined. Contour
maps and profiles of the water table can be prepared from elevations of water
in wells that tap the aquifer to determine the quantities of water available
and their distribution and movement. A special case of an unconfined aquifer
involves perched water bodies (Fig.1.1). This occurs wherever a groundwater
body is separated from the main groundwater by a relatively impermeable stratum
of small areal extent and by the zone of aeration above the main body of
groundwater. Clay lenses in sedimentary deposits often have shallow perched
water bodies overlying them. Wells tapping these sources yield only temporary
or small quantities of water.
CONFINED AQUIFERS: Confined aquifers also known as artesian or
pressure aquifers. Occur where groundwater is confined under pressure greater
than atmospheric by overlying relatively impermeable strata. In a well
penetrating such an aquifer, the water level will rise above the bottom of the
confining bed, as shown by the artesian and flowing wells. Water enters a
confined aquifer in an area where the confining bed rises to the surface; where
the confining bed ends underground, the aquifer becomes unconfined. A region
supplying water to a confined area is known as a recharge area; water may also
enter by leakage through a confining bed. Rises and falls of water in wells
penetrating confined aquifers result primarily from changes in pressure rather
than changes in storage volumes. Hence, confined aquifers display only small
changes in storage and serve primarily as conduits for conveying water from
recharge areas to locations of natural or artificial discharge.
Fig.1.1: Schematic Cross-sections of
Aquifer Types (Modified after Hartan et al, 1989)
LEAKY AQUIFER: Aquifers that
are completely confined or unconfined occur less frequently than do leaky, or
semi-confined, aquifers. These are a common feature in alluvial valleys,
plains, or former lake basins where a permeable stratum is overlain or
underlain by a semi-pervious aquitard or semi-confining layer. Pumping from a
well in a leaky aquifer removes water in two ways: by horizontal flow within
the aquifer and by vertical flow through the aquitard into the aquifer.
AQUITARD: An aquitard is a partly permeable geologic formation. It
transmits water at such a slow rate that the yield is insufficient. Pumping by
wells is not possible. For example, sand lenses in a clay formation will form
an aquitard.
AQUICLUDE: An aquiclude is composed of rock or sediment that acts
as a barrier to groundwater flow. Aquiclude are made up of low porosity and low
permeability rock/sediment such as shale or clay. Aquiclude have normally good
storage capacity but low transmitting capacity.
AQUIFUGE: These are a geologic unit that does not have
interconnecting pores, it is neither porous nor permeable thus can’t store or
give out water e.g. igneous rocks.
1.3 AIM
AND OBJECTIVES OF STUDY
This project
is aimed at delineating the depth to groundwater using vertical electrical
sounding (VES) with the Schlumberger electrode configuration in the Sports
Complex
Federal University of Petroleum
Resources Effurun, Delta state.
The Objectives of Study are:
1.
To detect subsurface layering and its resistivity
2.
To investigate the hydrological conditions of the area
with the view of delineating the potential area for groundwater development.
1.4 SIGNIFICANCE
OF STUDY
The Significance of the Study is important in following ways:
• It
will provide useful information on the ground water potential of the subsurface
in the area of study, to aid the site for productive boreholes.
• Geo-electric
details of the subsurface gotten from this study will give sound knowledge of
the subsurface geology such as the subsurface layering and its resistivity,
hydrological conditions and the structural geology.
1.5 SCOPE
OF STUDY
The scope of study was directed
towards data acquisition through Vertical Electrical Sounding (VES) carried out
in the study area alongside data interpretation to investigate the subsurface
geologic characteristics for delineating a good aquifer.
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