AN UNDERGRADUATE SEMINAR

ON

GROUND WATER EXPLORATION IN IGARRA

AREA

BY

JOSEPH IDODIA EDE

PSC2003846

TO

THE DEPARTMENT OF GEOLOGY,

FACULTY OF PHYSICAL SCIENCES,
UNIVERSITY OF BENIN,
BENIN CITY.

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OUTLINE
 INTRODUCTION
 AIM AND OBJECTIVES
 GEOLOGIC SETTINGS
 LITERATURE REVIEW
 METHODS OF GROUNDWATER EXPLORATION
 TRADITIONAL METHOD
 WHY TRANDITIONAL METHOD FAILED
 MODERN METHOD
 BENEFIT OF MODERN EXPLORATION
 RISK ASSESSMENT
 CONCLUSION
 REFERENCES

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 INTRODUCTION
 The consideration of the various sources of
water has revealed the qualitative advantage of
groundwater over surface water, because of the
deeper aquifer body layer occurrence of the
groundwater which makes the earth layer a
protective material or filter against easy
exposure to contamination process from human
activities thereby making it an important
renewable resource.
 For this reason, the importance of groundwater
has been well known to be useful for several
domestic and industrial activities.
 An essential component of groundwater
development ‘‘which has been a major concern’’
is the identification of potential areas/regions in
basement areas such3 as Igarra, where its
INTRODUCTION CONT’D
 In the search for safe and reliable groundwater
sources in basment terrian like Igarra,
geologists pay close attention to the underlying
geology of the area. Because areas with
fractured basement and thick regolith are more
promising for groundwater exploration

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AIM AND OBJECTIVES
AIM
To understand the geology of the area of study
as concerning exploration of water

OBJECTIVES
To articulate the exploration of groundwater in
basement area

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GEOLOGICAL SETTINGS
 The Igarra basement complex lies within the
pan african mobile belt.
 The basement area consist of both
metamorphic and igneous rocks.
 The area consist of regional metamorphic rock
namely; the Schist belt, Metaconglomerate,
schistose Quartzite, Calc-Silicate-Gneiss, etc.
And dynamic rock namely; fault Breccia.
 The Igarra crystalline rocks are generally
believed to be formed during the pan African
orogeny (650 Ma ± 150), which is known as
the older granite, the rock types are leuco
granite, pegmatite, biotite granite etc.
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GEOLOGICAL SETTINGS CONT’D
 The basement rock of this area has
undergone multiple phases of deformation,
metamorphism, and weathering, resulting in
a complex structural and hydrogeological
framework.
 The rock has low primary permeability, but
secondary permeability is enhanced through
fractures, faults, and weathered zones.
 The area has a mix of shallow and deep
aquifers with varying levels of productivity
and water quality, recharged primarily
through rainfall and surface water runoff.

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Fig 2: A geological map of
southwestern Nigeria

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LITERATURE REVIEW
 In 2015 Amigun et al., combined Landsat imagery
and geophysical survey to evaluate groundwater
potential in okenene and its environs.
 Similarly in 2020 Amigun et al., used geographic
information system(GIS) and remote sensing to
identify lineaments and fractures that could serve
as conduits for groundwater flow.
 Also in 2013 Abdullahi et al., conducted electrical
resistivity tomography (ERT) and ground-pentrating
radar (GPR) surveys to delineate aquiferous zones
in igarra area.
 In 2014 Agunleti et al., used vertical electrical
soundings (VES) and satellite imagery to identify
lineaments and fractures that could indicate
groundwater presence.
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 METHODS OF GROUNDWATER
EXPLORATION
Historically, different method has been employed
in exploring for ground water in basement terrain
like the Igarra area.
We are introduced to two sets of method which are;

TRADITONAL METHOD
 Dowsing (divining rod)
 Suface feature

MODERN METHOD
 Electrical Resistivity Tomography (ERT)
 Remote Sensing
 Ground Penetrating Radar (GPR)

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TRADITIONAL METHOD
Dowsing (Divining Rods): This method
involves using a Y-shaped rod believed to
point towards underground water sources.
However, it lacks scientific basis and is
considered a pseudoscience.
Surface Features: Observing surface
features like vegetation patterns or
presence of springs can be an indicator of
potential water sources. However, in
complex geological environments like
basement complex areas, these features
can be misleading and unreliable.
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Fig 3: dowsing rod

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 WHY TRADITIONAL METHOD
FAILED
Focus on Superficial Signs:
Traditional methods often focus on
surface indications, which may not
accurately represent the deeper
groundwater situation in basement
complex areas with limited fractures
and low porosity.
Lack of Scientific Basis: Methods
like dowsing lack scientific foundation
and have no proven effectiveness in
locating groundwater.
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MODERN METHOD
 Electrical Resistivity Tomography (ERT):
Electrical Resistivity Tomography (ERT) is a
geophysical technique that measures the
electrical resistivity of the subsurface to identify
areas with high conductivity, indicating potential
groundwater bearing zones
 Remote Sensing: Satellite imagery can be used
to identify areas with higher groundwater potential
based on land cover and vegetation patterns.
 Ground Penetrating Radar (GPR): It is a non-
invasive technique that uses radar pulses to
image the subsurface, which helps in identifying
subsurface structures and potential groundwater
bearing zones.
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Fig 4: Remote sensing field readings

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BENEFIT OF MODERN EXPLORATION
 Using combination of multiple datasets and
advanced analytics allows more accurate
identification of potential targets, reducing
exploration risk and cost.
 Modern exploration can identify potential
hazards like faults, fractures, or topography
ensuring safer exploration and extraction
operations.
 Modern method also help in analyzing and
producing detailed images of the subsurface,
helping to identify structures and potential
resource locations. Such methods involves
techniques like electrical resistivity, remote
sensing, ground penetrating radar etc.
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RISK ASSESSMENT
 Basement complex rocks are typically less
porous and permeable than sedimentary rocks,
this can lead to low groundwater yields.
• Groundwater in basement complex areas can be
unevenly distributed, concentrated in fractures
and weathered zones within the rock. This
uneven distribution can make it difficult to
locate productive groundwater zones and can
lead to dry holes.
• Basement complex rocks can contain
contaminant which can be human or natural
contaminant (fluoride, arsenic), which pose
serious health risks if consumed without proper
treatment.
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Fig 5: contamination process of ground water

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Fig 6: A model of boreholes drilled in contaminated and
uncontaminated zone

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CASE STUDY
 In2021 Adediran O.A et Al ., conducted a
groundwater investigation using an electrical resistivity
method at Igarra comprehensive high school.

MATERIALS
 Ohmega resistivity meter
 - 4 metallic electrodes (2 current, 2 potential)
 - 4 connecting cable reels
 - Measuring tape
 - Hammers
 - Compass
 - Cutlass
 - Data sheet
 - GPS

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Methodology:
Vertical Electrical Sounding (VES) technique;
 Schlumberger array with maximum half spread length (AB/2)
of 100m
 18 VES acquired across the study area
 Field data used to derive sounding curves and geo-electric
parameters

Results:
Sounding curves, tables, charts, maps, and geo-electric sections
are various ways of presenting the data;
 Curve types: H, QH, KH, KQH, KHA, and HA showing different
shapes of the sounding curves, indicating different geological
structures and materials.
 Predominant curve type: H (44.4%) the most common curve
type, indicating a high resistivity material is prevalent in the
area
 Geo-electric parameters derived from each VES has specific
values of resistivity and thickness for each layer at each VES
station.
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Fig: A table showing the 18 VES derived
parameters

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Fig: Pie chart showing percentage frequency of curve types within
the study area.

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CLASSIFICATION
The geo-electric sections showed four layers;
topsoil, weathered layer, weathered basement,
and fresh basement rock. The thickness and
resistivity of these layers varied across the area.
The study found;

 Topsoil: 0.5-1.5m thick, resistivity 129.1-956.4

Ωm
 Weathered layer: 0.6-22.0m thick, resistivity
6.8-1491.1 Ωm
 Weathered basement: 0.5-11.7m thick,
resistivity 261.3-776.6 Ωm
 Fresh basement: resistivity 1515.6-2653.5 Ωm
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CLASSIFICATION CONT’D
The study area was classified into three zones based on
groundwater potential:

 High potential area (center of the study area): thick

overburden (>22.0m) and low weathered basement
resistivity (338.0-526.6 Ωm)
 Medium potential area (85% of the total area):
moderate overburden thickness and resistivity values
 Low potential area (remaining 15%): thin overburden
and high weathered basement resistivity.

The study identified the central area as having high

groundwater potential, making it a suitable location for
drilling boreholes

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Fig : Geo-electric section along W
–E

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Fig : Geo-electric section along SW –
NE

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CONCLUSION
The igarra basement area presents a complex
hydrogeological environment with ground water
occurrence largely controlled by the fractured and
weathered basement rocks.
The integration of remote sensing, GIS, and
geophysical techniques has proven to be effective in
identifying potential groundwater-bearing structures
and defining aquiferous boundaries/zones. The results
of this study highlight the methods used in
groundwater exploration and demonstrate the
potentials for sustainable groundwater development
in this region.
However further investigation is needed to fully
understand the hydrogeological dynamics and to
optimize groundwater exploitation.
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 REFERENCES
Abdullahi, A. K.; Olorunfemi, M.O.; and Ojo, J.S. (2013).
Electrical resistivity tomography and ground-penetrating radar
surveys for groundwater exploration in the Igarra a Ojoawo,
A.O., and Oladapo, M.I. (2018). Groundwater exploration in
Aaba residential area of Akure, Nigeria. Hydrosphere.

Adeoti, L.O.; Oyedele, K.F. and Ojo, J.S. (2020). GIS and
re Ojoawo, A.O., and Oladapo, M.I. (2018). Groundwater
exploration in Aaba residential area of Akure, Nigeria.
Hydrosphere.

Agunleti, Y. S.; Adesina, A.K.; and Ojo, J.S. (2014).

Structural analysis of digitized lineament from satellite
imagery and vertical electrical soundings (VES) studies for
groundwater exploration in part of Nasarawa state, Nigeria.
Journal of Hydrogeology.
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 REFERENCES
Aluko, O.E., and Igwe, O. (2018). Automated geological
lineaments mapping for groundwater exploration in the
basement complex terrain of akoko-edo, Nigeria area, using
remote sensing techniques. In ground water exploration and
management .mote sensing techniques for identifying
groundwater potential zones in the Igarra area, Nigeria. Journal
of Geology and Mining Research.

Amigun, J. O.; Ojo. J.S.; Adebayo, S.O.; And Adesina,

A.K. (2015). Integrated Landsat imagery and geophysical
exploration for groundwater potential evaluation of Okene and
its environs, Southwestern Nigeria. Journal of Hydrogeology.

Ojoawo, A.O., and Oladapo, M.I. (2018). Groundwater

exploration in Aaba residential area of Akure, Nigeria.
Hydrosphere.
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THANKS FOR
LISTENING

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