Geoelectrical and Hydrochemical Assessment of Groundwater for Potability in Ebonyi North, Southeastern Nigeria

Geoelectrical and Hydrochemical Assessment of Groundwater for Potability in Ebonyi North, Southeastern Nigeria
Geoelectrical and Hydrochemical Assessment of Groundwater
for Potability in Ebonyi North, Southeastern Nigeria
1Onwe I. M, *2Otosigbo G. O., 3Eluwa N.N., 4Nkitnam E. E.
1,2,3,4Department of Physics/Geology/Geophysics, Alex Ekuweme Federal University, Ndufu-Alike, Ebonyi State, Nigeria
Geoelectrical and hydrochemical investigations were carried in order to determine the potentials
and quality of groundwater in Ebonyi North, Southeastern Nigeria. These methods were also
selected to determine their economy and accuracy compared to seismic method. Fifteen (15)
vertical electric sounding (VES) survey were conducted using the Schlumberger configuration in
order to evaluate the character of the aquifers in the studied locations while twelve (12)
groundwater samples were collected from boreholes for hydrochemical analysis. Geoelectric
sections derived from modelling of the VES data with the interpex IX1D software reveal 3 to 5
subsurface layers. The lithologic succession comprises of topsoil, lateritic clay, partially
weathered, weathered and fractured Asu River shale. The weathered and fractured layers
constituted the productive water bearing or aquiferous zones of good groundwater potentials.
Hydrochemical analysis of groundwater samples reveals that the pH range from 7.8 to 8.8,
electrical conductivity from 10.0 to 1754.00 μS/cm, total dissolved solid from 10.0 to 786.0 mg/l
and total hardness from 14.0 to 271.0 mg/l. The analytical results present the concentration of the
ions in the following order: Mg > Ca > Na > K and Cl > SO4 >HCO3> NO3 > CO3. Piper trilinear
diagram reveals only one water type, with Ca and Cl as the major dominant ions. The major ions
concentrations are within recommended standard for drinking, hence the groundwater from the
area is suitable for drinking and domestic purposes.
Keywords: Electrical resistivity, Groundwater potential, Drinking purpose, Hydrochemical assessment, water quality
INTRODUCTION
Water is very vital in many aspects of human life. Its
availability in the right quality and quantity is integral to
supporting socio-economic development and vital
ecosystems which depend upon it (Offodile, 2002;
UNESCO, 2006). Despite it being limited in quantity in
some parts of the earth, natural and anthropogenic
activities are further threatening its availability and
suitability for multiple uses (Pietersen et al., 2009). Surface
water has suffered most from both anthropogenic and
climate change (Zhang et al., 2010). As a result,
groundwater has become a more important and
dependable alternative of water supply (MacDonald et al.,
2012). According to Morris et al. (2003) more than 2 billion
people rely on groundwater for their basic water needs, the
study area not exempted with over 88 % of its population
depending on groundwater as source of water supply for
drinking and domestic purposes. Lack of potable water
posed serious challenges in the area which has result to
waterborne disease outbreaks that has led to lose of life of
inhabitant early March, 2017 (MOH, 2017).
Mineralogical composition of the underlying rock (s), and
the nature of the surface run-offs are factors that affect
quality of groundwater (Edet and Ekpo 2008; Amadi et al.,
2010). Olatunji et al., (2001) and Abimbola et al., (2002)
established that geology has a role to play in the chemistry
of subsurface water. Vertical electrical sounding (VES)
survey has been extensively employed in groundwater
investigation across the world, both in basement and
sedimentary terrains (Akaolisa, 2006; Tizro et al., 2010;
Arabi et al., 2010). Odoh and Onwuemesi (2009),
characterizing the anisotropic properties of the fractures of
the Abakaliki shales, showed that there is significant
anisotropy between 0 - 50 m depths, with fractures at
depths of 28.3, 40 and 50 m striking NE - SW, NW - SE
and N-S, respectively, and a better permeability and
*Corresponding Author: Otosigbo Gloria Ogochukwu,
Department of Geology, Federal University, Ndufu-Alike,
Ikiwo, Ebonyi State, Nigeria. E-mail:
gloriaotosigbo@gmail.com; Tel: +2348037137658
Research Article
Vol. 5(1), pp. 237-244, April, 2019. © www.premierpublishers.org. ISSN: 3019-8261
International Journal of Geology and Mining

Onwe et al. 238
porosity at the depth of 40 and 50 m. Odoh et al., (2012)
recommended an integrated geophysical approach in
investigating groundwater in the area in other to ensure
greater percentage of success in interpretation of field
results, since the groundwater in Abakaliki shales occur in
fractures, faults and/or weathered zones
It is imperative to evaluate the potentials of the underlying
formation and groundwater quality in the area as
dependable source of water alternative to surface water.
The study therefore, aimed at evaluate the geophysical
and hydrochemical data, and to assess the quality of the
groundwater with a view to determine the potability.
Location, Geology and Hydrogeology
The study area consists of Ngbo, Ezzangbo and Izzi parts
of the present Ebonyi north of Ebonyi State, Southeastern
Nigeria. The area is accessible through Enugu – Abakaliki
express road that lies between latitudes 6°301 N and 6°501
N, and longitudes 7°801 E and 8°001 E (Fig. 1). Geology of
the study area is predominantly shale facies of the
Abakaliki Shale (Agumanu 1989). The sediments have
been folded and fractured particularly following series of
tectonic episodes which have acted on them from the
Albian times; the fold axes stretch NW - SE (Benkhelil
1986). The lead - zinc mineralization in the Abakaliki -
Benue Trough occur in the fractures. Study area is
associated with lead - zinc mineralization. The evidence of
igneous/volcanic activities in the Abakaliki area (southern
Benue Trough) is represented by various intrusive
deposits and volcanoclastics in the study area.
Umeji (2000) has argued that the facture systems
originated from movement resulting from the rising and
cooling of magma, which intruded the sediments during
the Santonian epirogeny which created uplifts in the
Abakaliki and subsidence in both flanks of the Abakaliki
Anticlinorium which resulted in the formation of Anambra
and Afikpo Synclines. The high level of induration of the
shales, which has made some people use them for
construction works, have been interpreted as low grade
metamorphism (Obiora and Charan 2011).
Hydrogeologically, the major part of the study area is
underlain by aquiclude; except in locations where
secondary aquiferous conditions were made possible by
syn and post depositional circumstances. The syn-
depositional circumstance is the occurrence of lenses of
sandstone or siltstone beds, while the post depositional
circumstances include weathering, fracturing or shearing,
and volcanic intrusions.
Figure 1. Location and Geologic map of the study area (insert: maps of Nigeria and Ebonyi State)

Int. J. Geol. Min. 239
MATERIALS AND METHODS
Vertical electrical sounding and hydrochemical studies
were employed in this work.
Vertical electrical sounding (VES)
Vertical electrical sounding (VES) surveys, was performed
using the Schlumberger electrode configuration. This
procedure is known to generate reliable shallow
subsurface stratigraphic contrasts. This technique uses
two pairs of electrodes technically referred to as the
current and potential electrodes connected to a resistivity
meter. The resistivity meter used during the investigation
was Omega manufactured by Allied Associate
Geophysical Ltd (Fig. 2). Fifteen (15) vertical electrical
soundings (VES) were carried out within the study area.
The current electrode spacing ranges from a minimum of
1 m to a maximum of 100 m, while the potential electrode
spacing varies between 0.25 m and 10 m. These values
were chosen to enable optimal mapping of both shallow
and deeply seated structures, assuming that penetration is
about 1/6 of maximum current electrode spacing. The
location and distribution of the VES stations were based
on the available space and accessibility (See Fig. 1). The
apparent resistivity (ρa) for the Schlumberger array was
calculated using equation 1(Loke 1999).
2
1 1 1 1
MN
a
VV
K
I I
AM BN AM BN


   
= =        
− − + 
 
(1)
Where, ρa is the apparent resistivity (ohm-metre), ∆V is the
potential difference (volt) and I is the electric current
(ampere), where K, is the geometrical factor that depends
on the arrangement of the four electrodes A, B, M and N.
The geometrical factor was calculated as:
2 2
2 2
2
2
AB MN
K
MN

    
−    
     =
 
 
 
(2)
The apparent resistivity data was plotted against half the
current electrode spacing (AB/2) in order to generate the
relevant geoelectric curves. The processing of the data
was enhanced with the use of interpex IX1D software,
which enabled the generation of the sounding curves
(Nkitnam et al 2015). Geoelectric sections were drawn
using the information obtained from the sounding curves
while aquifer thickness was estimated from the geoelectric
sections. Corresponding lithologies for the geoelctric
section were inferred using the charts presented by (Loke
1999; Kearey et al., 2002).
Figure 2. Instrument used during VES survey
Hydrochemical Investigation
Groundwater samples were collected from 12 boreholes
(Table 1) for hydrochemical analyses using pre-washed 2
L polythene plastic bottles. Physical parameters like pH,
temperature and electrical conductivity were determined in
the field due to their transient nature. The pH of the water
sample was measured with a pH-meter (ASTM D1293-12).
The temperature was read using mercury in glass
thermometer. The electrical conductivity was measured
using a Mark electronic switchgear conductivity meter
(APHA 2510B). All analyses were carried out at the
Department of Biochemistry, Federal University Ndufu-
Alike, Ikwo, Nigeria, using standard procedures (Nnamonu
et al., 2018). The evaluation of groundwater quality was in
accordance with regulatory standard (WHO 2011). Cations
(Na
+
, k
+
, Mg
2+
, Ca
2+
) were analysed using ASTM D511-
09A. Anions (NO3
-
, SO4
2-
, Cl
-
and HCO3
-
) were analyzed.
Cl
-
and SO4
2-
were determined by ASTM D4327-03, NO3
-
was determined by ASTM D3867-90A and HCO3
- was
analyzed by titration with sulphuric acid.
Table 1. Groundwater sample locations
S/No Location CODE Source Depth (m) Coordinate Elevation. (m)
1 Oguduano BH1 Borehole 45 6047IN 7082IE 118
2 Ephutekwe BH2 Borehole 40 6043IN 7083IE 101
3 Odebor BH3 Borehole 50 6041IN 7082IE 108
4 Ndiagu Okwoeze BH4 Borehole 42 6033IN 7082IE 110
5 Ekweburu BH5 Borehole 50 6037IN 7088IE 86
6 Akpagu BH6 Borehole 45 6039IN 7086IE 90
7 Ndaburuebenyi BH7 Borehole 40 6043IN 7087IE 107
8 Umuoboke BH8 Borehole 38 6047IN 7087IE 117
9 Ikpomkpuma BH9 Borehole 43 6047IN 7093IE 118
10 Umuogudu BH10 Borehole 46 6045IN 7097IE 101
11 Umuegara BH11 Borehole 50 6042IN 7097IE 108
12 Ndulo BH12 Borehole 35 6035IN 7096IE 110

Onwe et al. 240
RESULTS AND DISCUSSION
Vertical Electrical Soundings
Interpreted curves from the VES data are shown in Figure
3. Results of the curve matching were studied in details to
estimated aquifer layer parameters (Table 2). The curve
type shows that the area is a multi-layer medium.
Results from the sounding curves reveals a succession of
three to five complete geoelectric layers. The curve types
obtained in the study area include; Q, H, QH, HA, HK and
KHK types reflecting lithological variation in the area. The
H- type curve is the predominant in the study area
constituting 34% of the total number of the VES curve. It
was observed in five points VES 6, 7, 9, 10 and 13. The H
- curve has an intermediate layer of low resistivity value,
which is weathered or fracture unit at particularly VES
locations. The extent to which the rocks have been
weathered or fractured determines the amount of water to
be found and these in turn govern the electrical resistivity
values (Nwankwo et al., 2004). This weathered or fracture
layer constitutes the hydrogeologically significant layers in
the area because of its water bearing capacity and
characterized by high porosity, relatively and high
permeability.
The HA- type curve is a four layer model of the subsurface
and was observed in VES 2, 3 and 14. The first layer is the
topsoil, followed by a dry shale formation and the
weathered layer in that order. The weathered layer in these
sequences is very favourable for groundwater abstraction.
Another curve type is KHK curve and it was observed only
in VES 4. The curve type is characterized by a steady
decrease in resistivity value. This curve type does not
guarantee the possibility of abstracting water in substantial
quantity from the VES point were the weathered layer is a
clayey formation which is an aquitard.
The geoelectric section was drawn across the fifteen (15)
VES stations in the direction that approximately N-E. The
litho-resistivity data of the area indicate that the first layer
across the VES locations has apparent resistivity values
that vary from 43.84 to 636.1 Ωm with mean value of
290.18 Ωm and thickness values that range from 1.02 to
5.49 m. The second layer has apparent resistivity values
that vary from 0.08 to 188.9 Ωm with mean value of 36.11
Ωm and thickness value that ranges from 0.02 to 81.23 m.
The third layer has apparent resistivity values that vary
from 1.82 to 2922.5 Ωm with mean value of 434.76 Ωm
and thickness value that ranges from 3.9 to 42.97 m. The
layer is partially weathered and is moderately convenient
for groundwater accumulation. The fourth layer has
apparent resistivity values that vary from 13.29 to 3216.3
Ωm with mean value of 555.23 Ωm and thickness value
that ranges from 4.16 to 33.06m. The fourth layer is very
favourable and productive for borehole construction. The
weathered/fracture zone gives rise to convenient flow
condition of water. The fifth layer has apparent resistivity
values that vary from 4.30 Ωm. This section indicates low
resistivity value and is a clayey formation, which is an
aquitard.
Hydrochemical analysis
The analytical results for groundwater samples from study
area are presented in Tables 3. Figure 4 shows a typical
Piper trilinear plot of hydrochemical parameters of
groundwater samples. Results indicated that temperature
varied from 27.00 to 29.00 0C with a mean value of 28.50
0C. Electrical conductivity observed to vary from 10.0 to
1754.00 μS/cm with an average value 712.5 μS/cm. The
value indicates that the borehole is in contact with more
dissolved inorganic constituents. The pH value varied from
7.8 to 8.8 with an average of 8.33, this suggests that the
groundwater quality is alkaline in nature.
Figure 3. Sounding curves from the study area

Table 2. Interpreted layer parameters of VES data of Ndaburuebenyi area
VES No Location Sequence of layers Curve type No of Layers
VES1 Ikpomkpuma 𝑝1 > 𝑝2 > 𝑝3 Q 3
VES2 Okwo 𝑝1 > 𝑝2 < 𝑝3 < 𝑝4 HA 4
VES3 St. Peter Catholic 𝑝1 > 𝑝2 < 𝑝3 < 𝑝4 HA 4
VES4 Ekweburu 𝑝1 < 𝑝2 > 𝑝3 < 𝑝4 > 𝑝5 KHK 5
VES5 Ndulo 𝑝1 > 𝑝2 < 𝑝3 > 𝑝4 HK 4
VES6 Ndiagu Onwe-eke 𝑝1 > 𝑝2 < 𝑝3 H 3
VES7 Umuoboke 𝑝1 > 𝑝2 < 𝑝3 H 3
VES8 Ndaburuebenyi 𝑝1 > 𝑝2 < 𝑝3 > 𝑝4 HK 4
VES9 Ogwuduano 𝑝1 > 𝑝2 < 𝑝3 H 3
VES10 Ephutekwe 𝑝1 > 𝑝2 < 𝑝3 H 3
VES11 Umuegara 𝑝1 > 𝑝2 > 𝑝3 < 𝑝4 QH 4
VES12 Umuogudu 𝑝1 > 𝑝2 > 𝑝3 < 𝑝4 QH 4
VES13 Akpegu 𝑝1 > 𝑝2 < 𝑝3 H 3
VES14 Ndiagu Okwoeze 𝑝1 > 𝑝2 < 𝑝3 < 𝑝4 HA 4
VES15 Odebor 𝑝1 > 𝑝2 > 𝑝3 Q 3
Table 3. Result of the hydrochemical analysis
Sample
No
Temp
(0
C)
pH TDS
(mg/l)
EC
(μS/cm)
TH
(mg/l)
TA
(mg/l)
Ca2+
(mg/l)
Mg2+
(mg/l)
Na+
(mg/l)
K+
(mg/l)
Fe2+
(mg/l)
Zn2+
(mg/l)
Mn2+
(mg/l)
HCO3
-
(mg/l)
SO4
2-
(mg/l)
Cl-
(mg/l)
NO3
-
(mg/l)
CO3
2-
(mg/l)
SAR
BH1 29.0 8.5 786 1754 172 640 31 141 6.0 0.60 0.42 0.01 0.13 20.8 48 167 0.62 0.14 0.647
BH2 29.0 8.2 188 432 89 164 35 55 27.0 0.51 2.89 0.17 0.33 6.5 27 82 0.74 0.07 4.025
BH3 29.0 8.0 10 10 171 380 50 222 6.4 1.80 0.45 0.01 0.17 7.5 26 105 0.75 0.13 0.549
BH4 29.0 8.2 388 753 102 310 21 181 11.6 1.50 0.36 0.01 0.03 7.5 21 112 0.76 0.12 1.154
BH5 29.0 8.5 415 754 36 384 8 28 6.2 0.40 0.44 ND ND 5.6 54 131 0.74 0.01 1.461
BH6 29.0 8.3 213 495 177 190 31 147 4.0 1.50 0.44 0.01 0.29 5.6 42 150 0.74 0.05 0.424
BH7 27.0 8.3 654 1240 41 476 25 16 8.4 5.00 0.46 0.01 ND 8.5 36 136 0.50 0.09 1.856
BH8 29.0 8.4 397 857 76 327 25 51 3.6 0.70 0.54 ND 0.03 5.5 63 70 0.47 0.06 0.584
BH9 29.0 8.3 282 644 164 274 56 108 9.0 0.90 1.77 0.26 0.12 5.2 50 160 0.62 0.05 0.994
BH10 27.0 8.7 338 922 140 294 30 110 2.0 0.20 0.55 0.01 0.22 7.3 63 147 0.73 0.05 0.239
BH11 28.0 7.8 35 42 14 15 35 10 2.4 0.80 0.40 0.01 0.10 2.5 21 42 0.62 0.04 0.506
BH12 28.0 8.3 386 647 105 365 24 126 3.0 1.50 0.46 ND ND 5.0 32 124 0.73 0.04 0.346
WHO(2011
)
- 6.5-
8.5
1200 1250 75 - 75 50 200 55 0.3 - 0.1 - 500 250 50 -
Minimum 27.0 7.80 10.0 10.0 14.0 15 8.0 10.0 2.0 0.2 0.40 0.01 0.03 2.5 21 42 0.47 0.01 0.239
Maximum 29.0 8.30 786.0 1754 177 640 56.0 222 27.0 5.0 2.89 0.26 0.33 20.8 63 167 0.76 0.14 4.025
Mean 28.5 8.30 341.0 712.5 125.6 318.4 30.9 99.6 7.5 1.3 0.79 0.05 0.13 7.29 40.25 118.8 0.67 0.07 1.065
Std. Dev. 0.83 0.28 224.7 477.6 96.0 157.7 12.7 68.1 6.8 1.3 0.80 0.09 0.12 4..53 15.34 38.3 0.1 0.04 1.051
TDS = total dissolved solids; EC = electrical conductivity; TH = total hardness; mg/L = milligram per litre. Dev. = Deviation;
Std. = Standard
Qualitative analysis of the groundwater samples shows
ionic concentrations in the following order: Mg > Ca > Na
> K and Cl > SO4 > HCO3 > NO3 > CO3. TDS result show
that groundwater in area is fresh water base on Hem
(1985). Total hardness value indicates that groundwater in
the area is hard (Table 4). Hardness in groundwater is
caused mostly by dissolved Ca2+ and Mg2+ ions which
primary results from dissolution of limestone or dolomite
from the soil and rock material (Yusuf 2007). TDS and total
hardness provide a rough indication of the overall
suitability of water for general purpose.
Chloride values ranges from 42.0 to 167.0 mg/l, with mean
value of 118.36 mg/l. Sulphate value ranges from 21.0 to
63.0 mg/l with mean of 40.25 mg/l, followed by bicarbonate
(2.5 - 20.8 mg/l), with the mean value of 7.29 mg/l; Nitrate
values ranges from 0.47 to 0.76 mg/l, with mean value of
0.67 mg/l. These values are much below the WHO (2011)
standard (50 mg/l) for NO3
- in domestic/public water
supply. Carbonate value ranged from 0.01 to 0.14 mg/l
with a mean value of 0.07 mg/l. Magnesium dominate the
cations with a mean value of 99.58 mg/l, followed by
calcium, with mean value of 30.92 mg/l. Next to calcium is
sodium with a mean value of 7.47 mg/l followed by
potassium with mean value of 1.28 mg/l. Trace metal
levels in the groundwater samples were in minor quantities
when compared to major cations and anions. Fe had the
highest mean concentration (0.792 mg/l). The noticeably
high concentration of Fe in the area can be attributed to
factors influencing iron solubility and concentration in
groundwater based on Okiongbo and Douglas (2013).
Quality of groundwater analysis and severity of the health
effects associated with water was classified according to
Richard’s (1969), sodium absorption ratio (SAR) scale. All
groundwater samples have SAR < 10 meq/L and on the
basis of Richard’s (1969) scale, presumed safe health
wise (Table 4).

Onwe et al. 242
Table 4. Rating of the studied groundwater samples using various scales
Water type rating Water hardness rating Health risk rating
Range of TDS
Values (mg/l)
Water typea Total hardness (CaCO3
in mg/l)
Water typeb SAR Values
(meq/l)
Effectc
0 - 1000 Fresh Water < 15 Very soft < 10 No problem
1000 - 10000 Brackish Water 15 - 60 Soft water 10 - 18 Increasing
problem
10000 -1000000 Saline Water 61 - 120 Medium-hard 18 - 26 Severe problem
> 1000000 Brine Water 121 - 180 Hard - -
- - > 180 Very hard - -
a
Hem’s (1985) TDS scale, b
Linsley et al.’s (1992) total hardness scale, c
Richard’s (1969) sodium absorption ratio (SAR) scale
Table 5. Ionic Ratios and CEV of Groundwater in the Area
S/No HCO3/Cl Cl/HCO3 Na/Ca Na/Cl Mg/Cl K/Cl Mg/Ca CEV
1 0.1245 8.0288 0.1935 0.0359 0.8443 0.0035 4.5483 0.9605
2 0.0792 12.6153 0.7714 0.3292 0.6707 0.0062 1.5714 0.6645
3 0.0714 14.0000 0.1280 0.0609 2.1142 0.0171 4.4400 0.9219
4 0.0669 14.9333 0.5523 0.1035 1.6160 0.0133 8.6190 0.8830
5 0.0427 23.3928 0.7750 0.0473 0.2137 0.0030 3.5000 0.9496
6 0.0373 26.7857 0.1290 0.0266 0.9800 0.0100 4.7419 0.9633
7 0.0625 16.0000 0.3360 0.0617 0.1176 0.0367 0.6400 0.9015
8 0.0785 12.7272 0.1440 0.0514 0.7285 0.0100 2.0400 0.9386
9 0.0325 30.7692 0.1607 0.0562 0.6750 0.0056 1.9285 0.9381
10 0.0496 20.1369 0.0666 0.0136 0.7482 0.0013 3.6666 0.9850
11 0.0595 16.8000 0.0685 0.0571 0.2380 0.0190 0.2857 0.9238
12 0.0403 24.8000 0.1250 0.0241 1.0161 0.0120 5.2500 0.9637
Minimum 0.0325 8.0288 0.0666 0.0241 0.1176 0.0013 0.2857 0.6645
Maximum 0.1245 30.7692 0.7750 0.3292 2.1142 0.0367 8.6190 0.9850
Mean 0.0621 18.4158 0.2875 0.0723 0.8302 0.0115 3.4359 0.9161
Ionic relationship was assessed to check the salinity and
origin of the groundwater in the area. Ionic relationship
assesses include: Na/Cl, Mg/Ca, Cl/HCO3, and the
Cationic Exchange Value (CEV = [Cl - (Na + K)]/Cl). The
molar ratio of Na/Cl ranges from 0.0241 to 0.3292, with
mean value of 0.0723. All the samples have Na/Cl molar
ratio less than 1, which indicates that ion exchange is the
major process. The Mg/Ca ratio ranges from 0.2857 to
8.6190, with mean value of 3.4359. All boreholes except
BH7 and BH11 are generally greater than 2, indicating the
transformation of fresh groundwater to saline in locations
of the study area. The Cl/HCO3 values range from 8.028
to 30.769. Values of this hydrogeochemical index given for
inland waters are between 0.1 and 5 and for seawater
between 20 and 50 (Custodio, 1987). In general, the CEV
for seawater ranges from +1.2 to +1.3 (Custodio, 1983),
where low-salt inland waters give values close to zero,
either positive or negative. The CEV values for
groundwater of the study area are generally below 1.0
(Table 5), ranging from 0.66 - 0.98, indicating that the
groundwater is inland in some locations with respect to
provenance.
The plot of HCO3/Cl versus TDS (Fig. 4) showed that the
regression slope was negative in the high (>500 mg/l) TDS
concentration range while the slope was positive in the low
(<500 mg/l) TDS concentration range indicating that
groundwater with high TDS concentration was enriched
with chloride and groundwater with low TDS concentration
was not. The variations of Ca/Na and Mg/Ca ratios with
TDS (Figs. 5 and 6) showed a similar trend and were
subsequently subject to a similar interpretation opposite to
plot of HCO3/Cl versus TDS. The shallow borehole of the
area was characterized by relatively low salinity and weak
concentrations of chloride compared to the deep borehole
water.
Information generated from the hydrochemical analysis of
the different groundwater samples were plotted on a Piper
trilinear diagram (Fig. 4). The Piper diagram has been
described as the most appropriate diagram for
interpretation of composite of groundwater parameters
(Freeze and Cherry 1979; Hounslow 1995). The dominant
ions (Na+, K+, Mg2+, HCO-
3, Cl-, SO2-
4 and NO-
3) were
plotted. The results show Ca-Cl type with Ca and Cl as the
major dominant ion. CaCl2 water type indicates water
mixing; mixing of the initial CaHCO3 with saline water and
it denotes water of paramount hardness.

Figure 4. A typical Piper trilinear plot of hydrochemical
parameters of water samples
CONCLUSIONS
Electrical resistivity survey was conducted in order to
delineate the subsurface structures that are favourable for
groundwater occurrence. Weathered and fractured
horizons have been identified in the area constitute the
aquifer zones. Good prospects therefore exist for
groundwater development in some area of the study where
the depth to aquifer zone is relatively thick and has
favourable low resistivity, while those with thin depth to
groundwater potential and high resistivity value have a
lower potential for an aquifer. The productive groundwater
zones are identified at the eastern part of the area.
Hydrochemical analysis revealed that the groundwater is
within moderately alkaline and mostly hard in nature. The
slightly high average electrical conductivity (712.50μS/cm)
of the water samples implies that some of the groundwater
samples are saline rather than fresh in nature. Majority of
chemical constituents are within the drinking limits.
Magnesium values were exceptionally high in some of the
groundwater samples studied. Piper trilinear plot revealed
that there is just one type of water (CaCl2) with Ca and Cl
as the major ions in the area.
The use of electrical resistivity and hydrochemical analysis
should be encouraged for its economy and accuracy
compared to other means of determining water portability
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Accepted 10 January 2019
Citation: Onwe IM, Otosigbo GO, Eluwa NN, Nkitnam EE
(2019). Geoelectrical and Hydrochemical Assessment of
Groundwater for Potability in Ebonyi North, Southeastern
Nigeria. International Journal Geology and Mining 5(1):
237-244.
Copyright: © 2019: Onwe et al. This is an open-access
article distributed under the terms of the Creative
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