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The International Journal Of Engineering And Science (IJES)
|| Volume || 4 || Issue || 11 || Pages || PP -29-39|| 2015 ||
ISSN (e): 2319 – 1813 ISSN (p): 2319 – 1805
www.theijes.com The IJES Page 29
Geophysical Investigation for Groundwater Potential in Rufus Giwa
Polytechnic Owo, Southwestern Nigeria
1O.O. Falowo,
2A.O. Daramola ,
3O.O. Ojo
1,2,3Department of Civil Engineering, Faculty of Engineering Technology, Rufus Giwa Polytechnic,
Owo, Ondo State, Nigeria.
------------------------------------------------------------ABSTRACT---------------------------------------------------------------
Geophysical investigation was conducted at Rufus Giwa Polytechnic, Owo, Southwestern, Nigeria with the aim of
evaluating the groundwater potential in the area. The geophysical survey involved Very Low Frequency
Electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES). A total of twenty seven (27) traverses were
established along West – East and Southwest – Northeast direction in the studied area; covering a total distance of
8.45 km. The lengths of the traverses vary between 110 m and 920 m. Measurements were taken at 10 m spacing
along the traverses for the VLF-EM. The result of the VLF-EM was used to determine the data point for the VES.
The VLF-EM result reveals the presence of conductive zones. The geoelectric section revealed 3 to 5 major layers
comprising the topsoil, clay, laterite, weathered layer, partly weathered layer/fractured basement, and fresh
basement rock. The topsoil has resistivity that varies between 46 Ω-m and 1644 Ω-m, and depth that ranges from 0.3
m to 19.8 m. It is composed of clay/sandy clay, clayey sand, lateritic clay and laterite. The clay substratum has
resistivity that ranges from 20 to 95 Ω-m and depth that varies from 1.5 m and 9.3 m. Laterite is characterized by
resistivity that varies between 106 Ω-m and 1223 Ω-m with thickness that varies from 0.8 m to 11.4 m. The
weathered layer which constitutes the first aquiferous zone and is characterized by resistivity that ranges between
28 Ω-m and 823 Ω-m, while its thickness varies from 0.4 m to 144.2 m. The composition of the weathered layer is
predominantly clayey sand indicating an aquitard i.e. a subsurface geological formation that stores but fairly
transmit water. The partly weathered layer/Fractured aquifer is the second aquiferous zone; it has resistivity that is
between 16 Ω-m and 914 Ω-m with thickness in the range of 0.3 m to 148.6 m. The fresh basement has resistivity
values that vary from 327 Ω-m to 17578 Ω-m. The low resistivity values (< 500 Ω-m) are due to screening effect by
the overlying conductive material. The weathered layer and fractured basement aquifers correlate the suspected
water filled geologic formation observed by the VLF-EM. Therefore the area shows a very good prospect for
groundwater development.
Keywords – aquiferous zone, conductive material, geological formation, geophysical investigation, groundwater
------------------------------------------------------------------------------------------------------------- -------------------------------
Date of Submission: 14 November 2015 Date of Accepted: 30 November 2015
-------------------------------------------------------------------------------------------------------------------------- ------------------
I. INTRODUCTION Access to clean water is a human right and a basic requirement for economic development. The safest kind of water
supply is the use of groundwater. Groundwater accounts for about 98 % of the world‟s fresh water and is fairly
evenly distributed throughout the world. It provides a reasonable constant supply which is not completely
susceptible to drying up under natural condition unlike fresh water. Water from beneath the ground has been for
domestic use, irrigation and livestock. Lakes, swamps, reservoirs and rivers account for 3.5 % and soil moisture
accounts for only 1.5 % ([4]).
The works of ([1], [3]) revealed that it is necessary to monitor water quality on regular basis. Since groundwater
normally has a natural protection against pollution by the covering layers, only minor water treatment is required.
Detailed knowledge on the extent, hydraulic properties, and vulnerability of groundwater reservoirs is necessary to
enable a sustainable use of the resources. The total replenishable water resource in Nigeria is estimated at 319 billion
cubic metres, while the groundwater component is estimated at 52 billion cubic metres. Nigeria has adequate surface
and groundwater resources to meet its current water demands. However, in spite of the tremendous efforts put by the
various Governments to improve access to potable water supply to all Nigerians, estimates shows that only 58% of
the inhabitants of the urban and semi-urban areas and 39% of rural areas have access to portable water supply.
Geophysical Investigation for Groundwater Potential…
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Water shortages are acute in some major centres and in numerous rural communities due to a variety of factors
including variations in climatic conditions, drought increasing demands, distribution system losses, and breakdown
of works and facilities. Other challenges facing the sector include funding constraints for improving and
rehabilitating broken down schemes, competition between water users, pollution from point and non-point sources
and lack of competent and skilled human resources.
1.1 Description of the Project Environment
Rufus Giwa Polytechnic, Owo, Ondo State, is located in Owo “Fig. 1” which is within the south western part of
Nigeria. The institution “Fig. 2” is situated in Owo local Government of Ondo State “Fig. 3”. It lies within
longitudes 6 ̊ 00ˡ E and 5 ̊ 30ˡ E and latitudes 7 ̊ 30ˡ N and 7 ̊ 00ˡ N. The study area is easily accessible by roads like
Ikare – Owo highway, Benin – Ifon highway and Akure – Owo highway.
1.2 Geomorphology, Climate and Vegetation
Owo is relatively flat, as the terrain ranges from 940 ft to 1100 ft “Fig. 4”. The terrain slopes from Rugipo down to
Isuada town “Fig. 5”. Elevation is much higher at Ikare Junction and lower around Emure and Isuada towns. In
RUGIPO, the topography ranges from 311 m to 342 m above the sea level. The study area has a gently undulating
topography. The area lies geographically within the tropical rain forest belt of hot and wet equatorial climatic region
characterized by alternating wet and dry climate seasons ([6]), which is strongly controlled by seasonal fluctuation
in the rate of evaporation.
The available rain data shows that mean annual rainfall ranges from 1000 mm - 1500 mm and mean temperature
of 24 ̊ C to 27 ̊ C. There is rapid rainfall during the month of March and cessation during the month of November.
June and September are the critical month when rainfall is usually on the high side. The vegetation is of tropical
rainforest and is characterized by thick forest of broad-leaved trees that is ever green. The vegetation of the area
(especially in undeveloped areas) is dense and made up of palm trees, kolanut trees and cocoa trees. Part of this area
is also made the school farm.
1.3 Geology of the Studied Area
The area of study falls within the Southwestern basement rock “Fig. 6” which is part of Nigerian Basement
complex. The area is underlain mainly by rocks of the Migmatite - Gneiss Complex “Fig. 7”. RUGIPO is
predominantly underlain by quartzite, granite and granite gneiss “Fig. 8”.
Quartzite is the most dominant rock; which mineralogically contains quartz dominating mineral, other minerals
such as muscovite, tremolite, microcline and biotite are common as well. Quartzites which are prominent as ridge
vary in texture from massive to schistocity due to the presence of flaky minerals like mica.
II. METHODS OF STUDY Twenty seven traverses were established in W-E and SW-NE direction with length that varies between 110 m and
920 m “Fig. 9”. The total length of the traverses established is 8450 m (8.45 km).
Figure 1: Road/Administrative Map of Ondo State
IgbekeboIgbokoda
Ore
IreleOkitipupa
Okeluse
Ute
Ifon
Ipele
Sanusi
OkpeEmure
Sasere
AyereOke-Agbe
Auga
Ise
IbilloIsua
OkaIkare
Ikun
AfoIdoani
Akungba
IkunOgbagi
Arigidi
Oba
Uso
IjuIta ogbolu
Ijare
Akotogbo
OtuOmotosoKajola
Oniparaga
Ode-Aye
Igbotaku
LodaAyadi
Ondo
Ibagba
Asewele
OminiaOdigbo
Ofosu
Omifunfun
Jimgbe
Odole Ala-Ajagbusi
Oba-IleAkure
Onikoko
Araromi
Ile-Oluji
AladeIdanre
ESE-ODO
ILAJE
IRELE
OKITIPUPA
ODIGBO
ONDO-WEST
IDANRE
ILE-OLUJI
Bolorunduro
IFEDORE
AKURENORTH
OWOOSE
AKOKO SW
AKOKO NE
AKOKO NW
AKOKO SE
EDO STATE
EKITI STATE
OSUN STATE
OGUNSTATE
DELTA STATE
KOGISTATE
ATLANTIC OCEAN
MAIDUGURI
ENUGU
MAKURDI
ILORIN
SOKOTO
KANO
LAGOS
AKUREIBADAN
ABUJA
N
L. Gov't. Headquarters
Towns & Villages
Minor Road
Major Road
6 00o
5 30o
5 00o
4 30o
6 00 Eo
4 30 Eo
5 00o
5 30o
6 00 No
6 30o
7 00o
7 30 No
6 00 No
6 30 No
7 00o
7 30o
State Boundary
025 25 Km
Geophysical Investigation for Groundwater Potential…
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Figure 2: Land-Use Master Plan of RUGIPO
Figure 3: Map of Owo Local Government Area of Ondo State
O.S.P.O. CONSULT
ACTIVITY AREA
AREA FOR
FUTURE
AGRICULTURAL
DEVELOPMENT
GAMES RESERVE
RESERVATION
O.S.P.O. CONSULT ESTATE AREA
MANAGEMENT STAFF QUARTERS
NEW SPORTCOMPLEX
Ata
mopere
Strea
m
AGRICEXTENSION AREA
ARTIFICIAL LAKE
STAFFCLUB
HOSTEL
HO
ST
EL
SCHOOL OF BUSINESSSTUDIES
SCHOOL OFGENERALSTUDIES
SCHO
OL O
F
ENG
INEER
ING
TECHNO
LOG
Y
SENIOR STAFF
QUARTERS
EXPANSION
Ope
Stream
JUNIOR S
TAFF QUARTERS
COMMERCIAL SCHOOL OF FOODTECHNOLOGY
CENTRAL AUDITORIUM/ADMINISTRATIVE/CONFERENCE CENTRE
PLACE OFWORSHIP CENTRAL
POOL
OSPO. COMM. CEN.
RESEARCH/PRESS CENTRE
PART-TIME STUDENTS RESERVATION
DAM
ETFRESERVATION AREA
From Akure
To Oluku
C.S
REC
NC
STAFFCLUB
G.H.
MAINTENANCE DEPT.
O.S.P.O.GUESTHOUSE
PLACE OFWORSHIP
W.T.
SUB.
ALUMNICENTRE
344000E 345000 346000 347000 348000 349000 350000E
344000E 345000 346000 347000 348000 349000 350000E
356000N
357000
358000
359000
360000
361000
361250N
356000N
357000
358000
359000
360000
361000
361250N
Quarry
Aau
nke
Str
eam
Gate
560m0 560 1120 1680m
Existing Road
Boundary Pillar
Fence
Proposed Roads
Streams
Trees and Hedges
Commercial Centre
Faculties/ConferenceCentres
Administrative Blocks/Conference Centres
School Boundary
Hostel
Management Staff QuartersLecture Halls/Existing Buildings
New Sport Complex
Artificial Lake/Pond
StadiumGate
R.C. Recreation Ground
S.U.B. Student Union Building
C.S. Corner Shop
O.S.P.O. Ondo State Polytechnic, Owo
W.T. Waste Treatment
Ceded Land
LEGEND
MAIDUGURI
ENUGU
MAKURDI
ILORIN
SOKOTO
KANO
LAGOS
AKUREIBADAN
ABUJA
N
AK
UR
E N
OR
TH
L.G
.A.
IDA
NR
E L
.G.A
.
AKOKO SOUTH WEST L.G.A.
OS
E
L.G
.A.
EKITI STATE
Igbatoro
Alafiatayo
AraromiSanusi
Emaajomo
IseweOkififioko
Daji Camp
Sasere
Ago-Panu
Ipeme
Ipele
Iyere
Baga
Eporo
Obasoro
IlaleAlasa
IjegunmoOlefa
Igodi
Oluka
Odofin-Alaro
Alaga
EmureRUGIPO
Uso
Ago-Panu
Amurin
Ipele Junction
Isijogun
5 15 E
5 15 E
7 30 N 7 30 N
6 00 E
6 00 E
6 45 N6 45 N
Major Road
Minor Road
Main Paths
RUGIPO
Towns and Villages
Rivers and Streams
LEGEND
0 5 Km
SCALE
Geophysical Investigation for Groundwater Potential…
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Figure 4: Topographical map of Owo and Environs
Figure 5: 3-D Surface Elevation Map around the studied Area
Geophysical Investigation for Groundwater Potential…
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Figure 6: Geological sketch map of Nigeria showing the major geological component; Basement,
Younger Granites, and Sedimentary Basins ([5]).
Figure 7: Geological Map of Owo and Environs, showing the Study Area ([5]).
Owo
Study Area
Geophysical Investigation for Groundwater Potential…
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Figure 8: Geological Map of RUGIPO
Figure 9: Data Acquisition Map of the Study Area
N
OSPO CONSULTESTATE AREA
CEDED AREA
Management Quarters
AREA FOR FUTUREAGRICULTURALDEVELOPMENT
AGRIC EXTENSIONAREA
HOSTEL
GAMES RESERVE
RESERVATION
Atam
oper
eSt
ream
STAFFCLUB HO
STEL
SCHOOL OF BUSINESSSTUDIES
SENIOR STAFF
QUARTERS
EXPANSION
Ope
Stream
From Akure
To Oluku
344000E 345000 346000 347000 348000 349000 350000E
344000E 345000 346000 347000 348000 349000 350000E
356000N
357000
358000
359000
360000
361000
361250N
356000N
357000
358000
359000
360000
361000
361250N
Quarry
560m 0 560 m
Quartzite
Granite Gneiss / Granite
Dam Quarry
Ceded Area
Stream
LEGEND
SUB
S.S.
ST
AD
IUM
ADMINISTRATIVE BUILDING
HEALTH CENTRE
FACULTY OF GENERAL STUDIES/MASS COMMUNICATION DEPT
School F
arm
LOW RISE
MANAGEMENT QUARTERS
356000N 347000E
357000
357750
348000E
0
To Akure
To Ifon
Road
Grid Lines
Gate
Traverse Line(VLF & Magnetic)
200 m
GUESTHOUSEARTISAN
LIBRARY
ICT
Hoste
l
Ho
ste
l
Block-Five
POULTRY
Millenium Lecture Theatre
CE
DE
D A
RE
A
Minor Path
VES Point
SCALE:
LEGEND
Stream
Tr.1
Tr.19
Tr.2Tr.3
Tr.4
Tr.5
Tr.6Tr.7
Tr.8
Tr.9
Tr.10
Tr.11
Tr.12
Tr.13
Tr.14
Tr.15
Tr.16
Tr.
17
Tr.18
Tr.20
Tr.21
Tr.22
Tr.23
Tr.24
Tr.25
School F
arm
School F
arm
Tr.26
Tr.27
Borehole Location
Hand Dug Well Location
B.Tech.Est. Mgt
V1 V2V3
V4 V5
V6
V7
V8 V9 V10
V11
V12V13
V14
V15
V16
V17
V18
V19
V20
V21
V22
V23
V24
V25
V26
V27
V28
V29
V30V31
V32
V33
V34 V35
V36 V37
V38 V39 V40V41
V42
V43V44
V45
V46 V47
V48 V49 V50 V51V52
V53
V54
V55
V56 V57 V58
V59
V60 V61
V62
V63
V64 V65V66
V67
V68
V69 V70
V71
V72V73 V74 V75
Tr.1 Traverse Number
V8 VES Number
VLF & MagneticData Point
Geophysical Investigation for Groundwater Potential…
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2.1 VLF-EM Survey
The VLF - EM method utilized the inline profiling technique. The measurements were taken at 10 m intervals along
each traverse. The ABEM – WADI EM-VLF was used for the measurements. Although both real and quadrature
components of the VLF-EM field were measured, the real component data, which are usually more diagnostic of
linear features, were processed. The real and filtered real components were plotted against stations position using
„KHFFILT‟ software version 1.0 ([7]). The 2-D modeling of the filtered real component was carried out using the
same software. The profiles were interpreted qualitatively by visual inspection of anomalies (conductor) that are
diagnostic of possible geological structures in the bedrock while the 2-D modeling output was used for quantitative
interpretation.
2.2 Electrical Resistivity Survey
The electrical resistivity method utilized Vertical Electrical Sounding (VES) using the Schlumberger array. The
same traverses were used in each locality as in VLF method. Sounding stations were determined from conductive
zones delineated by the VLF – EM. The location of each sounding stations in both geographic and Universal
Traverse Mercator (UTM) coordinates was recorded with the aid of the GARMIN 12 channel personal navigator -
Geographic Positioning System (GPS) - unit. The instrument used for the resistivity data collection was the Omega.
The current electrode spacing (AB/2) was varied from 1 m to 225 m. The apparent resistivity(𝜌𝑎 ) resistivity
measurements at each station were plotted against electrode spacing (AB/2) on bilogarithmic graph sheets.
The resulting curves were then inspected visually to determine the nature of the subsurface layering. In each way,
each curve was characterized depending upon the number and nature of the subsurface layers.
Partial curve matching ([9]) was carried out for the quantitative interpretation of the curves. The results of the
curve matching (layer resistivities and thicknesses) were fed into the computer as starting model parameter in an
iterative forward modeling technique using RESIST version 1.0 ([10]). From the interpretation results, geoelectric
sections along the traverses were produced. The interpreted result was considered satisfactory since a good fit of
RMS between the field curves and computer generated curves.
III. RESULTS AND CONCLUSION 3.1 Field Curves
The number of layers varies between 3-layers and 6-layers. Nine curve types have been identified in the study area:
KH, HKH, H, KHKH, QH, HK, KQ, AK, and KAH. The most occurring curve types identified are KH and HKH
curve types “Fig. 10”. The root mean square (RMS) error of the generated curves ranges between 1.8 and 10.7; this
shows models of well smoothened, iterated curves ([2]).
3.2. 2-D VLF – EM Modeling and Geoelectric
Section
The 2-D structure of the real component of the VLF – EM along Traverse 2 is shown in “Fig. 11a”. The 2-D
structure reveals one strongly conductive zone located around 45 and 87 m. This structure has a depth greater than
20 m. This conductive is suspected to be a thick weathered zone or fractured zone. The geoelectric section along this
Traverse shows that VES 1, 2 and 3 have thick weathered layer indicating good aquiferous unit for groundwater
prospect. The most occurring resistivity range of 400 Ω-m – 700 Ω-m suggests a clayey sand/sand formation which
is an aquitard i.e. a subsurface geological formation that can store water but poorly transmits.
“Fig. 12” displays the 2-D modeling of the VLF-EM and the geoelectric section along Traverse 8. The 2-D
model identifies a highly resistive body suspected to be an outcropping basement at 25 m; and water filled
geological formation with a highly weathered/fractured zone between distances 48 and 75 m and 10 and 40 m
respectively. The depth of this strongly conductive target ranges between 0 and 35 m. The zone will be good for
groundwater development.
Figure 10: Bar-Chat of Curve Types obtained from the Study Area
Geophysical Investigation for Groundwater Potential…
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(a)
(b)
Figure 11: (a) 2-D modeling; (b) Geoelectric section along Traverse 2
(a)
(b)
Figure 12: (a) 2-D modeling; (b) Geoelectric section along Traverse 8
20 40 60 80
320
325
330
335
Dep
th (
m)
Distance (m)
VES 6 VES 7
W E
199
575
52
3061
10
0
5 m
10 m
LEGEND
Partly Weathered Layer/Fracture Basement
Top soil
Fresh Basement
Resistivity785
Laterite Weathered Layer
( -m )
1644
283
136
661
20 40 60 80 100 120 140 160 180
310
315
320
325
330
335
340
345
Dep
th (m
)
171
VES 22 VES 23
VES 24
SW NE
141
719
1406
40
376
60219
1474
562
84
327
270
64
522
5 m
LEGEND
Weathered Layer 64Top soil
Partly Weathered Layer/Fractured Basement
Fresh Basement
Resistivity ( -m )20 m
Existing Borehole Location 4
0
Geophysical Investigation for Groundwater Potential…
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The geoelectric section “Fig. 12b” along this Traverse revealed that weathered layer and the fractured basement
(unconfined) constitute the major aquifers as evidenced by the existing boreholes under VES 24 with resistivity that
ranges between 64 Ω-m and 562 Ω-m; and 40 Ω-m and 522 Ω-m respectively. The composition of the weathered
layer is predominantly clayey sand. The thickness of the weathered layer varies from 5 m to 50 m.
The 2-D structure of the real component of the VLF – EM along Traverse 10 is shown in “Fig.13a”. The 2-
D structure reveals a strongly conductive zone suspected to be water filled geological formation with a highly
weathered /fracture zone at distances between 70 and 115 m. The 2-D also identified a very poor conductive zone
typical of lateritic hard pan between distances 10 and 60 m. Both have a depth extent greater than 20 m. The 2-D
model corroborates the thickly weathered layer (with thickness greater than 20 m) under VES 29 but thin under VES
28. The resistivity of this weathered layer which constitutes the major aquifer unit along this Traverse varies from 28
Ω-m to 229 Ω-m
“Fig. 14” displays the 2-D structure of the real component of the VLF-EM and the geoelectric section along
Traverse 12. The top of the main conductive target (at distance 80 m) as indicated by the 2-D model correlates with
the geoelectric section “Fig. 14b” which identifies this target as a low resistivity (< 50 Ω-m) suspected to be a clayey
material.
The 2-D structure of the real component of the VLF – EM along Traverse 21 is shown in “Fig. 15a”. It
identifies a strongly conductive feature suspected to be water filled geological formation/weathered zone or
fractured zone at distances between 15 m and 45 m. This conductive target has a depth extent of 25 m. The
geoelectric section delineates this feature as a low resistivity geomaterial composed of clay weathered layer and
clayey sand as the topsoil. Therefore, the aquifer unit along this Traverse is clay with resistivity that is generally less
than 100 Ω-m.
“Fig. 16” displays the 2-D structure of the real component of the VLF-EM and the geoelectric section along
Traverse 25. The 2-D “Fig. 16a” model identifies a strongly conductive cross cutting linear feature at distance 400
m. This conductive target has a depth extent greater than 60 m. The presence of this cross cutting linear structure is
indicative of weak/incompetent geologic formation. However, on the geoelectric section beneath VES 66 where this
cross cutting feature occurred, it‟s revealed as fractured basement at a shallow depth (less than 10 m).
IV. CONCLUSIONS Geophysical investigation of Rufus Giwa of Rufus Giwa Polytechnic has been carried out, with the aim of
evaluating the groundwater potential of the institution. The 2-D modeling real component of the VLF-EM revealed
the presence of conductive zones which were used as data points for the vertical electrical soundings. The
geoelectric section revealed 3 to 5 major layers comprising the topsoil, clay, laterite, weathered layer, partly
weathered layer/fractured basement, and fresh basement rock. The weathered layer and fractured basement aquifers
correlate with the suspected water filled geologic formation as lineated by the VLF-EM. Therefore the area has a
good prospect for groundwater development.
REFERENCES [1] A.F. Abimbola, O.M Ajibade, A.A. Odewande, W.O. Okunola, T.A. Laniyan, and T.T. Kolawole, Hydrochemical Characterization of
Water Resources around the Semi-Urban Area of Ijebu-Igbo Southwestern, Nigeria. Journal of Water Resources Vol.20, 2008, 10-15.
[2] R. Barker, L. Blunt, and I. Smith, Geophysical consideration in the design of U.K. National Sounding Database. First Break, Vol. 14,
1996, No. 2, pp. 45-53. [3] A.E. Edet, and O.E. Offiong, Surface Water Quality Evaluation in Odukpani, Calabar Flank, Southwestern, Nigeria. Journal of
Environmental Geology, 36 (3/4), 1998b: 343–348.
[4] R.A. Freeze, and J.A. Cherry, Groundwater (Prentice-Hall, Englewood Cliffs, New Jersey, 1979), 604. [5] Geological Survey of Nigeria, Geological map of Akure Area, Sheet 61. Geological Survey Department, Ministry of Mines, Power
and Steel, Nigeria. 1966.
[6] N.P. Iloeje, A new geography of Nigeria (New Revised Edition) Longman Nig. Ltd., Lagos, 1981, 201pp. [7] KHFFILT, Karous-Hjelt and Frazer filtering of VLF measurements, Version 1.1a, Markku Pirttijarvi, 2004.
[8] Ondo State Surveys Akure, Nigeria. Administrative map of Ondo State, Ministry of works and Housing, Akure Ondo State, Nigeria,
1998. [9] E. Orellana, and H.M. Mooney, Master Tables and Curves for Vertical Electrical Sounding over Layered Structure, Geophy. Prospect
29, 1966: 932-955.
[10] B.P.A Vander Velper, Resist Version 1.0, M.Sc. research Project ITC Delf. Netherlands, 1988.
Geophysical Investigation for Groundwater Potential…
www.theijes.com The IJES Page 38
(a)
(b)
Figure 13: (a) 2-D modeling; (b) Geoelectric section along Traverse 10
(a)
(b)
Figure 14: (a) 2-D modeling; (b) Geoelectric section along Traverse 12
40 60 80 100
310
315
320
325
330
335
De
pth
(m
)
Distance (m)
VES 28 VES 29
SW NE
331
50
229
16
2498
82726
46
284
0
5 m Partly Weathered Layer/Fracture Basement
Fresh Basement
20 m Top soil Weathered Layer
58 Resistivity ( -m )
LEGEND
30 35 40 45 50 55 60 65 70 75 80 85 90
300
310
320
De
pth
(m
)
Distance (m)
VES 31VES 32
51683
14979
19
3941
651258
20
14478
LEGEND
Resistivity
Partly Weathered Layer/Fracture Basement
ClayTop soil
Fresh Basement
5 m
10 m
0
( -m)19
Geophysical Investigation for Groundwater Potential…
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(a)
(b)
Figure 15: (a) 2-D modeling; (b) Geoelectric section along Traverse 21
(a)
(b)
Figure 16: (a) 2-D modeling; (b) Geoelectric section along Traverse 25
20 40 60 80 100 120 140 160 180 200 220 240 260
290
300
310
320
330
Dept
h (m
)
VES 52
VES 53 VES 54369
251
93
17578
538305
38
105
278240
Distance (m)W E
Weathered Layer
Fresh Basement
20 m
10 m
0
105 Resistivity ( -m )
Top Soil
Partly Weathered Layer/Fracture Basement
50 100 150 200 250 300 350 400 450 500 550
280
300
320
340
Dep
th (m
)
VES 64VES 65
VES 66 VES 67
Distance (m)
229
247 302 627
936618501
901
207
163252
355
907 752
914
7581
Fresh Basement
50 m LEGEND
Weathered Layer
Resistivity
Partly Weathered Layer/Fracture Basement
20 m
Top soil Laterite
252 ( -m )
W E
0