ABSTRACT
In a bid to determine the groundwater potential of some parts Orsu and environs, which lies within latitude N5º53.858΄ to N5º47.572΄ and longitude E7º0.847΄ to E6º56.988΄, a total of ten (10) vertical electrical soundings were carried out. The study area belongs to the Anambra basin which is one of Nigeria’s most important hydrological basins. It is overlain by the Miocene to recent Benin formation and Eocene Ameki formation.Equipment such as ABEM terrameter SAS 4000, 12volts battery, global positioning system (GPS), four electrodes, reel of cables, clip, hammer etc were used during the data acquisition process and were processed using FORTRAN 2D Resistivity inversionSoftware. Moreso, Surfer 14 program was used to provide the transmissivity, hydraulicconductivity, diffusivity, and storativity maps, as the imaging pictures of the subsurfacein the form of contour maps. Results from the processed data revealed that the study areaconsist of top soil, sand, clayey sand and clay. Out of a total of 10 Vertical electricalsoundings obtained from selected locations in the study area, All VES points indicated a5-layer curve except VES 3 and VES 5 which have shown a 7-layer lithology. VES 2 and6 has shown KH curve type (i.e. ρ1< ρ2> ρ3> ρ4< ρ5 characteristic), VES 4, VES 7 andVES 8 has also shown HA (i.e. ρ1> ρ2< ρ3< ρ4< ρ5 characteristic). VES 1, VES 9 and VES10 have shown KA, AK & HK curves respectively. However, from analyses made,greater part of the region is prolific (that is, high groundwater potential). The depth towater from VES 1 to VES 10 were estimated as 92.8m, 87.0m, 91.0m, 104.0m, 139.0m,139.93m, 214.0m, 137.0m, 67.0m, 37.0m respectively. Shallow aquifer systems wereencountered at areas such as: Akwakuma Okporo, Okwuruokwuo Amannachi, UmualumIsiafor Ofeahia, Umuoka Asaa, and Amaruru , while deep aquifer systems were seen atareas such as: Afor-Iduu Amaebu Ebenator, St. peters, Umuezeala Amaebu, Umuhu-Okabia, Umucheke Omuokabia Awo-Idemili, Uda Orsu-Ihiteukwa. Areas such asAmannachi, Ebenator, Amaebu and Isiafor ofeahia are highly prolific and have shownhigh level of transmissivity of about 3000 to 4000m2/day and high storativity rangingfrom 0.0004 to 0.00058. These areas have also shown high rate of diffusivity with valueranging from 5500000 to 8500000, except Amaebu which have shown very low level ofdiffusivity.Keywords: Groundwater, Vertical Electrical Sounding, Transmissivity, HydraulicConductivity, Diffusivity, and Storativity
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Abstract vi
Table
of Contents vii
List of Figures x
List of Plates xi
List of Tables xii
CHAPTER ONE: INTRODUCTION
1.1 Background Information 1
1.2 Aim and Objectives 2
1.2.1 Aim 2
1.2.2 Objectives 2
1.3 Location and Accessibility 2
1.4 Justification of Study 5
1.5 Climate
and Vegetation 5
1.6 Geological
settings of the study area 6
1.6.1 Regional
Geology 6
1.6.2 Local Geology of the study area 6
1.6.2.1 Benin formation 6
1.6.2.2 Ameki formation 7
1.7 Groundwater
9
1.8 Porosity
and Permeability 10
1.8.1 Porosity 10
1.8.2 Permeability
11
1.9 Aquifer and Aquiclude 12
1.10 Scope
and Limitations of the study 13
1.11 Relief 14
CHAPTER TWO: LITERATURE REVIEW
2.1 Previous
works 15
2.2 Review of Geoelectric techniques 16
CHAPTER
THREE: MATERIALS AND METHOD
3.1 Desk
study 18
3.2 Reconnaissance survey 18
3.3 Detailed study 18
3.4.1 Global
positioning system (GPS) 19
3.4.2 ABEM
Terrameter (SAS 4000) 19
3.4.3 Electrodes 20
3.4.4 Cables 20
3.4.5 Clips 20
3.4.6 Hammer 21
3.4.7 Rollers 21
3.4.8 Protective
wears 21
3.4.9
Matchet 21
3.4.10
Compass 21
3.5 Field
Procedures 21
3.6 Data
Presentation 23
3.7 Principles
of Electrical Resistivity Method 24
3.8 Theory
of Electrical Resistivity in rocks 25
3.9 Apparent
resistivity 27
3.10 Observed
Precautions 30
CHAPTER
FOUR: RESULT PRESENTATION AND
INTERPRETATION
4.1 Data processing 32
4.2 Qualitative interpretation 36
4.2.1 Description
of the various curve types 36
4.3 Quantitative interpretation 36
4.4 Profiles 37
4.4.1 Profile One (A-B) 37
4.4.2 Profile
Two (C-D) 39
4.4.3 Profile
Three (E-F) 41
4.5 Groundwater
Potential evaluation 43
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 48
5.2 Recommendation 50
References 51
Appendix I 56
Appendix II 66
LIST
OF FIGURES
Figure 1.1 Location map of the study area showing VES
locations 4
Figure
1.2 Geologic map of the study area 8
Figure 3.1 General four electrodes configuration for
resistivity
measurement, consisting of a pair of current
electrodes (A, B)
and a pair of potential electrodes (M, N) (Adapted
from
Lowrie, 1997). 28
Figure 4.1 Correlated Geoelectric section along profile
A-B 38
Figure 4.2 Correlated Geoelectric section along profile
C-D 40
Figure 4.3 Correlated Geoelectric section along profile
E-F 42
Figure 4.4 Aquifer thickness of the VES points in the study area 43
Figure
4.5 3D Contour map of the study area
showing
transmissivity
variations 44
Figure
4.6 3D Contour map of the study area
showing
Hydraulic
conductivity variations 45
Figure
4.7 3D Contour map of the study area
showing
Diffusivity
variations 46
Figure
4.8 3D Contour map of the study area
showing
storativity
variations 47
LIST
OF PLATES
Plate 3.1 ABEM Terrameter SAS 4000 20
Plate 3.2 Researcher
and some crew members during data
collection
at one of the VES points. 22
Plate 3.2 Data
acquisition process at VES 2
(Okwurukwuo
Amannachi, Orsu) 23
LIST
OF TABLES
Table 1.1 Geologic
Formation Outcropping at the study area 9
Table 1.2 Porosity and permeability of some geologic
materials
(after Montgomery, 1990). 12
Table 4.1 Vertical Electrical Sounding (VES) Summary 33
Table 4.2 Hydrogeophysical parameters of the study
area 34
Table 4.3 Layer resistivities at different 35
Table 4.4 Aquifer hydraulic parameters 35
Table 4.5 Qualitative interpretation of the data
obtained from the
study area 36
Wisdom, O (2019). Geo Electrical Assessment of Groundwater Potentials of Some Parts of Orsu and Environs, South Eastern Nigeria. Afribary.com: Retrieved January 23, 2021, from https://afribary.com/works/geoelectrical-assessment-of-groundwater-potentials-of-some-parts-of-orsu-and-environs-southeastern-nigeria
Obodo, Wisdom. "Geo Electrical Assessment of Groundwater Potentials of Some Parts of Orsu and Environs, South Eastern Nigeria" Afribary.com. Afribary.com, 07 Sep. 2019, https://afribary.com/works/geoelectrical-assessment-of-groundwater-potentials-of-some-parts-of-orsu-and-environs-southeastern-nigeria . Accessed 23 Jan. 2021.
Obodo, Wisdom. "Geo Electrical Assessment of Groundwater Potentials of Some Parts of Orsu and Environs, South Eastern Nigeria". Afribary.com, Afribary.com, 07 Sep. 2019. Web. 23 Jan. 2021. < https://afribary.com/works/geoelectrical-assessment-of-groundwater-potentials-of-some-parts-of-orsu-and-environs-southeastern-nigeria >.
Obodo, Wisdom. "Geo Electrical Assessment of Groundwater Potentials of Some Parts of Orsu and Environs, South Eastern Nigeria" Afribary.com (2019). Accessed January 23, 2021. https://afribary.com/works/geoelectrical-assessment-of-groundwater-potentials-of-some-parts-of-orsu-and-environs-southeastern-nigeria