ABSTRACT
The study was carried out to investigate the aquifer potentials and subsurface lithology in Akwa Ibom State Polytechnic Campus Ikot Osurua. The Study area lies between latitude 5ᴼ091 and 5ᴼ401N and longitude 7ᴼ181 and 7º201E. It is underlaid by sedimentary formation of late tertiary and holocence ages. A total of twelve (12) vertical electrical soundings (VES) were conducted using the integrated Geo-instrument Service (IGIS) resistivity meter to generate the field data. The schlumberger sounding was carried out with current electrode spacing (AB) ranging from 1-300 m. The distance used for the potential electrode spacing (MN) ranged from 0.25 -10 m. The field data obtained were subjected to interpretation by partial curve marching and then by computer iteration using IP12WIN software. The interpreted results were constrained by lithologic log to produce the geo-electric sections of the subsurface. The geoelectric section showed three(3) to five (5) layered subsurface of top soil, Lateritic sand, Consolidated Sand, Clay sand and aquifer layer with different curve types which were Q, KA, K, KK and HQ. Aquifer characterization of the area showed the aquifer resistivity and depths ranging from 30.6 to 6489 Ωm and 50 to 100 m respectively although it varies in some location, this is an indication of the presence of fresh groundwater.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table of Contents vi
List of Tables viii
List of figures ix
Abstract x
CHAPTER 1:
INTRODUCTION
1.1 Overview 1
1.2 Aim and
Objectives 2
1.3 Justification 3
1.4 Scope
of Study 3
1.5 Location
of the Survey Area 4
1.6 Geology
of the Study Area 8
1.7 Statement
of the Problem 8
CHAPTER 2:
LITERATURE REVIEW
2.1
Components of Vertical Electrical
Sounding (VES) 9
2.2
Electrode Arrangement in Resistivity
Survey 10
2.2.1
Schlumberger array configuration 10
2.2.2 Wenner configuration 13
2.2.3 Dipole –dipole configuration 15
2.3 Concept of Real and Apparent Resistivity 17
2.4 Assumption in Vertical
Electrical Sounding 17
2.5 Physical Properties of Rocks 19
2.5.1
Quantitative description of mechanical properties of rock 20
2.5.2 Thermal property 20
2.5.3 Electrical properties 21
2.6 Size of Rock Particles 21
2.6.1 Grain sorting 24
2.7 Electrical Resistivity Method 29
2.7.1 Resistivity of rock 29
2.8 Current and Potential Distribution in
the Earth 32
2.9 Resistivity Curves 33
CHAPTER 3: MATERIALS AND METHODS
3.1 Instrumentation 35
3.2 Reconnaissance Visits 35
3.3
Organization of The Field
Crew 36
3.4
Field Measuring
Procedures 39
3.5
Measurements and their
Resolution at the Field 40
3.6
Data Acquisition 41
3.7
Geoelectric Sections 41
CHAPTER 4: RESULT AND DISCUSSION
4.1 Presentation
of Results 48
4.2 Discussion 48
CHAPTER 5:
SUMMARY, CONCLUSION AND RECOMMENDATION
5.1 Summary 64
5.2 Conclusion 64
5.3 Recommendations 65
References
LIST
OF TABLES
2.1 Grain Size range of some
sedimentary particles 26
2.2 Mineral stability 27
2.3 Mineral composition 28
2.4 Resistivity of rocks 31
3.1 Summary of the VES location 38
4.1 Mean
resistivity values for the 12 VES points 51
LIST OF FIGURES
1.1a Map
of Nigeria showing the State of study area 5
1.1b Map of Akwa Ibom State showing LGA of survey
area 6
1.1c Map of Ikot Ekpene LGA showing the study
area 7
2.1 Schlumberger
Array 12
2.2 Wenner
Configuration 14
2.3 Dipole-dipole
configuration 16
2.4 Grain
Sizes 23
2.5 Basic
curve types 34
3.1 Map
showing the VES points, traverses in Akwa Ibom State Polytechnic 37
3.2 Geoelectric
section for VES points 2, 3, 11, 4, 1, 10. 43
3.3 Borehole
Lithology showing VES 3 AA1 44
3.4 Geoelectric
section for VES points 6, 9, 7, 12, 5, 8.
46
3.5 Borehole
Lithology log showing VES 6 of BB1 47
4.1 Model
Layer Curve for VES1 52
4.2 Model
Layer Curve for VES2 53
4.3 Model
Layer Curve for VES3 54
4.4 Model
Layer Curve for VES4 55
4.5 Model Layer Curve for VES5 56
4.6 Model Layer Curve for VES6 57
4.7 Model
Layer Curve for VES7 58
4.8 Model
Layer Curve for VES8 59
4.9 Model
Layer Curve for VES9 60
4.10 Model
Layer Curve for VES10 61
4.11 Model
Layer Curve for VES11 62
4.12 Model
Layer Curve for VES12 63
CHAPTER 1
INTRODUCTION
1.1 OVERVIEW
Quality and clean water resources
availability and affordability are among the key concerns in every part of the
world ranging from developed through developing to third world societies. Anomoharan
(2011), in describing groundwater submitted that it is water located below the
Earth surface in buried aquifer and streams. Life existence on Earth is largely dependent
on water, a natural resource. Clean and fresh water is a basic essentiality for
the continued existence, preservation and necessary for human development in
addition to environmental conservation. Often times, ground water is
pollution-free and the need may not arise for purification before deploying for
use (Lawrence and Ojo., 2012). As an
essential need for humans and animals, drinking is the principal purpose it
serves in addition to usage domestically. Its availability and non availability
suggests the quality of environmental nature which is a yardstick for measuring
life and economic programs (Akankpo et al.,
2008). In view of this, the yearning for quality water has picked up
tremendously worldwide owing to the growth in population, change in climate and
development in socio-economy.
Attention is place
on the exploration of groundwater resource, which is the largest available
source of quality fresh water held in the subsurface within the zone of
saturation under hydrostatic pressure below water (Ariyo and Banjo, 2008).
As a result of
modern technological advancement, its use has gained preferable choice
domestically and industrially with the need for a comprehensive knowledge of
formation and the characteristics of aquifer (Zohdy et al., 1974). Within this zone, it is of the essence to
verify if the aquifer is either subject to contamination or not. Hydrological
and geophysical studies are essential in such area of study in a bid to
accomplish this. Geological entity beneath the water table is enough store-house
capable of supplying adequate quantity of water at fast rates to wells. Aquifer
is the name given to such geological entity (Fetter, 1980). A salient non
permeable rock devoid of connectivity of pore, hence it is neither water
absorber nor transmitter which is known as aquifuge. Furthermore, there exists
an aquiclude which is a porous but non permeable formation that has the
capability to absorb water gradually but not transmitting it in ample quantity
to well or a spring. Nevertheless, it necessarily partakes in groundwater
movement regionally (Ward, 1975).
Different
researchers have successfully adopted various exploration methods for this
all-important natural resource. Gabr et
al., (2012) for example successfully employed a method known as seismic
refraction to probe the level of groundwater in Wadi Al-ain area, United Arab
Emirate. Geophysical surveys have been most widely used because of the basic
advantages of providing more accurate results than other methods. Areas of
clearly defined contrast in electrical conductivity between formation water
bearer and adjoining rocks can effectively be mapped using method of electrical
resistivity (Nejad, 2009). It entails
electric current sent into the subsurface that produces electrical potential,
which is measured in a bid to determine the resistivity of the subsurface.
1.2
AIM AND OBJECTIVES
This research work is aimed at:
1.
Investigating the aquifer
potentials and subsurface lithology in Akwa Ibom State Polytechnic Campus at Ikot Osurua.
This survey was
undertaken to achieve the following objectives.
1.
Thickness of the sediments and
subsurface lithology in Akwa Ibom State Polytechnic
Ikot Osurua Campus will be estimated
using vertical electrical sounding
(VES).
2.
Adequate information on the
hydrogeology system of the aquifer will also be provided.
1.3 JUSTIFICATION
The vertical electrical sounding
(VES), using the Schlumberger array has gain wider applications owing to its
easy cost effectiveness and easy data acquisition and interpretation among
numerous advantages as compared to other resistivity measurements. This method
has being veritable tool to mapping aquifer in all geologic terrains in the
country and beyond, (Ayolabi et al., 2003).
This study has
really help to identify through Geophysics the possible depth through which
groundwater could be tap and also the different lithology as we move from top
to bottom between maximum current electrode separations. It has contributed
tremendously towards understanding the terrains of Akwa Ibom State Polytechnic,
Ikot Asurua campus. Therefore a compressive evaluation of groundwater potential
and subsurface lithology of the area becomes necessary in order to make the
study area independent in its quest to provide a portable, reliable and
consistent water supply for the increasing population.
1.4
SCOPE OF STUDY
The study is on geoelectrical
investigation of aquifer potentials and subsurface lithology in Akwa Ibom State
Polytechnic Ikot Osurua campus (Akwapoly) in Akwa Ibom State. Vertical
electrical sounding (VES) method will be used for this research work. The study
will be limited to Schlumberger configuration only.
1.5 LOCATION OF THE SURVEY AREA
Ikot Osurua is one of the villages in
Ikot Ekpene L.G.A in Akwa Ibom State. The village is located in the southern
part of Nigeria between latitudes 50091 and 50 401N and longitudes 70181 and 70201E.
The town has an undulating nature and it is among the thick forest area but the
town is not flooded because of it relatively high elevation with respect to
nearby villages, towns and flowing streams of permeable topsoil.
The town is
accessible through a network of roads and bordered in the north by Atan Ikot
Okoro, south by Abiakpo Ntak Inyang, west by Uwa and east by Ikot Akpan Abia. The
map of Nigeria, Akwa Ibom State and Ikot Ekpene L.G.A which shows the location
of the study area in fig. 1.1a, 1.1b and 1.1c.
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