Journal of Water Resource and Protection, 2013, 5, 715-722
http://dx.doi.org/10.4236/jwarp.2013.57072 Published Online July 2013 (http://www.scirp.org/journal/jwarp)
Assessment of the Groundwater Quality in Parts of
Imo River Basin, Southeastern Nigeria:
The Case of Imo Shale and Ameki Formations
Ikechukwu B. Ijeh, Ifiok E. Udoinyang
Department of Physics, Michael Okpara University of Agriculture, Umudike, Nigeria
Received April 16, 2013; revised May 16, 2013; accepted June 14, 2013
Copyright © 2013 Ikechukwu B. Ijeh, Ifiok E. Udoinyang. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is
properly cited.
ABSTRACT
Hydro-geochemical survey is undertaken in parts of Imo River Basin, Southeastern Nigeria, particularly in the geo-
logic formations of Imo Shale and Ameki, to assess the quality of groundwater. Eleven samples of groundwater are ob-
tained from various boreholes in the study area and subjected to physico-chemical analysis using standard laboratory
techniques. The study is aimed at the assessment of the groundwater quality indicators namely: pH, electrical conduc-
tivity (N), phosphate (PO4), sulphate (SO4), nitrate (3
NO

) and total dissolved solids (TDS). The result shows that the
water from boreholes in Umuahia has low pH, and is therefore acidic. The pH values range between 4.40 and 5.60,
which is below the acceptable range of 6.5 - 8.5. The acidity probably results from carbonic acid derived from the solu-
tion of CO2 from both the atmosphere and the decomposition of plant materials in the soil zone. The acidity of the
groundwater gives slight sour taste to drinking water, due to the mobilization of trace metals from the aquifer material
into the groundwater system, because of the corrosive effect of acidic water. Since borehole supply is rarely treated,
these trace metals end up in domestic supplies resulting in health implications and complaints. Acidic waters are typi-
cally low in buffering calcium minerals, but are high in dissolved carbon dioxide gas, which can cause the low pH or
acidity. Calcite neutralizer tanks with natural crushed and screened pure calcium carbonate easily neutralize acidic wa-
ter from 6.0 to 6.9. Below 6.0 a blend of calcite and Corosex is recommended. Common systems used to treat low pH:
Calcite Neutralizer, calcite & Corosex Blend Neutralizer, pflow Neutralizer, Soda Ash Feed Pump Injection System.
Keywords: Hydro-Geochemical; Imo River Basin; Physico-Chemical Analysis; Groundwater Quality; Acidity
1. Introduction
Water is essential for livelihood as well as socio-eco-
nomic development of any community. Many communi-
ties in Nigeria, especially in the Imo River Basin area
rely on surface and groundwater for both domestic and
agricultural water supplies. Groundwater pollution is a
growing environmental problem, especially in develop-
ing countries. Many major cities and small towns in Ni-
geria depend on groundwater for water supplies, mainly
because of its abundance, stable quality and also because
it is inexpensive to exploit. However, the urbanization
process threatens the groundwater quality because of the
impact of domestic and industrial waste disposal. This
results in aquifer deterioration, since some of these waste
products, including sewage and cesspool may be dis-
charged directly into the aquifer system. Water soluble
wastes and other materials that are dumped, spilled or
stored on the surface of the land or in sewage disposal
pits can be dissolved by precipitation, irrigation waters or
liquid wastes and eventually seep through the soil in the
unsaturated zone to pollute the groundwater. Once con-
taminated, it is difficult, if not impossible, for the water
quality to be restored. Thus constant monitoring of
groundwater quality is needed so as to record any altera-
tion in the quality and outbreak of health disorders.
Groundwater quality depends, to some extent, on its
chemical composition (Wadie and Abduljalil, 2010)
which may be modified by natural and anthropogenic
sources [1]. Rapid urbanization, especially in developing
countries like Nigeria, has affected the availability and
quality of groundwater due to waste disposal practice,
especially in urban areas. Once groundwater is contami-
C
opyright © 2013 SciRes. JWARP

I. B. IJEH, I. E. UDOINYANG 716
nated, its quality cannot be restored by stopping the pol-
lutants from source (Ramakrishnaiah et al., 2009) [2]. As
groundwater has a huge potential to ensure future de-
mand for water, it is important that human activities on
the surface do not negatively affect the precious resource
(Sarukkalige, 2009) [3]. Poor environmental manage-
ment creates havoc on the water supply, hygiene and
exacerbating public health (Okoro et al., 2009) [4]. Tay
and Kortatsi (2008) emphasize on the importance of
groundwater globally as a source for human consumption
and changes in quality with subsequent contamination
can, undoubtedly, affect human health [5]. Acidified
groundwater has been reported from many parts of the
world particularly in North America and Europe [6-8]
(Hultberg & Wenblad, 1980; Appelo et al., 1982; Grim-
vall et al., 1986). Groundwater in most hard-rock aqui-
fers are also known to be vulnerable to quality problems
that may have serious impact on human health [9]
(Smedley et al., 1995). The rocks are often carbonate-
defficient and give rise to poorly buffered groundwater
(acidic groundwaters) that encourage the dissolution of
elements such as Al, Mn, Be and Fe from most minerals
if they are present in the rock matrix into the groundwa-
ter and make the groundwater unsafe for drinking [10]
(Kortatsi, 2003). Acidity of groundwaters can cause cor-
rosion problems leading to high maintenance costs and
shortened life of hand pumps and accessories. It can also
lead to high metal concentrations in the borehole that
may cause aesthetic problems and, in extreme cases,
physiological problems.
Geology of the Study Area
The study area, shown in Figure 1, lies between latitudes
5˚42'N and 5˚45'N and longitudes 7˚15'E and 7˚30'E.
Two geologic formations are covered in the study area,
namely: Imo shale and Ameki formations respectively.
Imo shale consists of a thick sequence of blue and dark
grey shales with occasional bands of clay-ironstones and
subordinate sandstones [11] (Swardt and Casey, 1961). It
dips at angles 17˚ to 25˚ to the south-west and South [12]
(Uma, 1986). It includes three constituent sandstones: the
Igbabu, Ebenebe and Umuna Sandstones with the last
two outcropping in the Imo River Basin. The Umuna
sandstone is composed of thick sandstone units and mi-
nor shales and is generally less than 70 m thick. The
Ebenebe Sandstone occurs as a lens in the northwestern
extremity of the Imo River Basin. It is similar in lithol-
ogy to the Umuna sandstone but is relatively thicker with
a maximum thickness of 130 m (Uma, 1986). Ameki
Formation (Eocene) consists of sand and sandstones. The
lithologic units of the Ameki Formation fall into two
general groups [13-15] (Reyment, 1965; Whiteman, 1982
and Arua, 1986); an upper grey-green sandstones and
sandy clay and a lower unit with fine to coarse sand-
stones, and intercalations of calcareous shales and thin
shelly limestone. The Imo River Basin has a large
amount of recharge; estimated at 2.5 billion m3 per an-
num, coming mainly from direct infiltration of precipita-
tion. Average annual rainfall is about 2000 mm [16]
(Onwuegbuche, 1993).
2. Methodology
Investigations of the pollution status of groundwater in
the study area were conducted recently by collecting wa-
ter samples from boreholes in different locations in the
Figure 1. Map of the study area show ing Imo Shale and Bende Ameki Formations.

I. B. IJEH, I. E. UDOINYANG 717
study area. Water samples from 11 randomly selected bo-
reholes in the study area were analyzed for chemical
quality at the UNICEF Water Project, Owerri, and Imo
State Environmental Protection Agency, respectively.
The result was geo-processed to obtain groundwater qua-
lity maps showing the spatial variation of pH, electrical
conductivity, sulphate, phosphate, total dissolved solids
(TDS), salinity, nitrate respectively. The samples were
stored in a sterilized 250 ml bottles and then taken to the
laboratory for analysis. The electrical conductivity, total
dissolved solids, Nitrate, sulphate, phosphate and salinity
were determined using a HA-CH 44600-00 Condutivity/
TDS meter at a temperature of 20˚C. These samples were
refrigerated and analyzed within 24 hours. All plastics
and glass wares utilized were pre-washed with detergent
water solution, rinsed with tap water and soaked for 48
hours in 50% HNO3 then rinsed thoroughly with dis-
tilled-deionized water. They were then air-dried in a dust
free environment. The pH was determined using a HA-
CH sensor 3 pH meter. The turbidity was determined
using a spectrophotometer. The result is presented in Ta-
ble 1.
3. Results and Discussion
The specific parameter maps of groundwater quality in-
dicators were developed to facilitate the rapid assessment
of the extent of pollution of the various locations within
the study area in terms of their respective concentrations.
Contour maps of the spatial variation of electrical con-
ductivity, phosphate, sulphate, salinity, total dissolved
solid, nitrate, and turbity were also developed [17].
3.1. pH
Figure 2 shows the map of the spatial variation of pH in
the study area. It can be seen from the map that much of
the area around Umuahia have pH lower than 6.00. From
the chemical data shown in Table 1, the pH values vary
from 4.40 to 6.70. Areas within Umuahia metropolis
show pH of 4.40 - 5.60. This indicates that the water is
acidic. They are not within the acceptable WHO range
for portable water (6.5 - 8.5) [18]. Only three boreholes
within the study area fall within the acceptable range,
BH21, BH28 and BH54 with pH of 6.5 - 6.7. The acidity
probably results from carbonic acid derived from the
solution of CO2 from both the atmosphere and the de-
composition of plant materials in the soil zone. The acid-
ity of the groundwater gives slight sour taste to drinking
water and has also led to the mobilization of trace metals
particularly iron, manganese, aluminium and arsenic into
the groundwater system, because of the corrosive effect
of acidic water. It is the amount and type of dissolved
minerals that give the groundwater its distinctive taste.
Since borehole supply is rarely treated, these trace metals
end up in domestic supplies resulting in health implica-
tions and complaints. Acidic waters are typically low in
buffering calcium minerals, but are high in dissolved
carbon dioxide gas, which can cause the low pH or acid-
ity.
3.2. Electrical Conductivity
The map of the spatial variation of electrical conductivity
is shown in Figure 3. Electrical conductivity of water is
Table 1. Groundwater quality data: imo shale and ameki formations.
S/N
borehole
number location longitude latitude pH
Electrical
conductivity
(μs/cm)
tds (mg/l)nitrate
(mg/l)
sulphate
(mg/l)
phosphate
(mg/l) salinity turbidity (jtu)
FMENV/WHO’S STANDARD 6.5 - 8.5100 250 45 250 5 50 50
1 BH 1 UMUOSU 7.16002 5.676986.44 54 27 0.1000.00 0.24 0.5 2
2 BH2 EZIAMA OSUAMA 7.17038 5.708005.88 77 38 4.1002.00 0.38 0.3 1
3 BH3 UMUDURU 7.23028 5.710925.77 68 34 3.1001.00 0.56 0.2 2
4 BH8 WINNERS UMUAHIA 7.51816 5.519075.45 52 26 0.9002.00 0.10 3.4 121
5 BH9 OHOKOBE UMUAHIA 7.50943 5.515804.80 72 36 0.5001.00 0.12 6.7 3
6 BH10 WBHE, UMUAHIA 7.49876 5.514254.82 85 42 0.2000.00 0.20 1.2 9
7 BH11 AZIKIWE RD, UMUAHIA 7.49733 5.525884.40 53 27 1.9001.00 0.34 1.8 8
8 BH12 AFARA UMUAHIA 7.48837 5.517255.60 77 38 1.1002.00 0.28 1.1 6
9 BH21 AMAIGBO 7.10723 5.723226.50 41.1 22.1 41.0011.20 - 18.516
10 BH28 UMUEZEALA-AMA 7.24280 5.675506.50 86.3 43.0 0.0010.58 12.5 0.3
11 BH54 UMUARIAM OBOWO 7.33831 5.554916.70 14.5 7.3 1.02 0.02 - 2.470.0

I. B. IJEH, I. E. UDOINYANG 718
Figure 2. Spatial variation of pH in the study area.
Figure 3. Spatial variation of electrical conduc tivity in the study area.
used as an indicator of how salt-free, ion-free, or impu-
rity-free the sample is; the purer the water the lower the
conductivity (the higher the resitivity). The World Health
Organization standard for acceptable electrical conduc-
tivity is 100 μs/cm. Pure water has an electrical conduc-
tivity of 5.5 μs/cm, a measure of the total dissolved solid
(TDS), while rain water and ocean water have 5000 to
30,000 μs/cm and 45,000 to 60,000 μs/cm respectively.
Normal groundwater has a range of 100 to 2000 μs/cm
[19] (Offodile, 2002). All areas within the study area fall
within the WHO standard for electrical conductivity.
3.3. Phosphate
Figure 4 shows the map of phosphate concentration in
the study area. Phosphorus is one of the key elements
necessary for the growth of plants and animals. Phos-
phates are not toxic to people or animals unless they are
present in very high levels. Digestive problems could
occur from extremely high levels of phosphate. The
WHO standard for phosphate in drinking water is 5 mg/l.
This standard is exceeded only in Umuezeala-ama, BH28
(12.50 mg/l). This is probably because of the extensive
use of fertilizer for farming in the area. The rest of the
area have generally low concentration of phosphate (≤2
mg/l), perhaps, due to less farming in those urban cen-
ters.
3.4. Nitrate
Figure 5 shows the contour map of spatial variation of
nitrate concentration in the study area. Nitrate is an es-
sential ingredient of plant nutrition. It is, however re-
garded as an indicator of pollution in public water supply

I. B. IJEH, I. E. UDOINYANG 719
Figure 4. Spatial variation of phosohate in the study area.
Figure 5. Spatial variation of nitrate in the study area.
[18] (Offodile, 2002). The WHO standard for nitrate in
drinking water is 50 mg/l. This standard is not exceeded
in any part of the area.
3.5. Sulphate
Figure 6 shows the map of the spatial variation of sul-
phate concentration in the study area. Sulphate occurs
mostly as Calcium Sulphate (Gypsum). Sodium and
Magnesium Sulphate are readily soluble in water while
Calcium Sulphate is less so. Sulphur is useful to plants
(Offodile, 2002). High levels of sulphate in drinking wa-
ter can cause diarrhea. The WHO standard for Sulphate
in drinking water is 250 mg/l. From the study no bore-
hole was found to have excess sulphate. The map shows
that the northeast quadrant of the study area and a bit of
the southeast have generally less concentration of sul-
phate than the west, northwest and south of the study
area.
3.6. Total Dissolved Solids
Figure 7 shows the map of the spatial variation of the
total dissolved solids (TDS) in the study area. The total
dissolved solids (TDS) provide a rough indication of the
overall suitability of water for whatever purpose. The
WHO standard for TDS in drinking water is 250 mg/l.
No borehole location exceeded the required maximum
standard. The map indicates higher values around Umu-
ezela-ama, Umuduru, and Eziama Osuama. This may be
due to increased pollution arising from increased fertili-
zation and industrial waste.

I. B. IJEH, I. E. UDOINYANG 720
Figure 6. Spatial variation of sulphate in the study area.
Figure 7. Spatial variation of total dissolved solid in the study area.
3.7. Turbidity
Figure 8 shows the contour map of the turbidity in the
study area. Turbidity is the amount of cloudiness in the
water. This can vary from a river full of mud and silt
where it would be impossible to see through the water
(high turbidity), to a spring water which appears to be
completely clear (low turbidity).Turbidity can be caused
by silt, sand and mud, bacteria and other germs, and
chemical precipitates. It is very important to measure the
turbidity of domestic water supplies, as these supplies
often undergo some type of water treatment which can be
affected by turbidity. Turbidity was measured in nephew-
lometric turbidity units (NTU), using a turbidity meter
because of its accuracy. The map shows that most of the
areas investigated are within acceptable WHO standard.
4. Conclusion
From the groundwater quality analysis, most of the
groundwater quality parameters measured are within
acceptable portable standards, except for the acidity of
the groundwater around Umuahia area. Umuahia is the
most densely populated part of the study area. The at-
mospheric condition of the city, possibly affected by in-
dustrial and domestic waste, may be the probable cause
of acidification of the groundwater. Virtually all ground-
water comes from precipitation that soaks into the soil
and passes down to the aquifer. Rainwater has a slightly
acidic pH, therefore it tends to dissolve solid minerals in
the soil and in the aquifer. Different rocks, e.g., sand-
stone, limestone and basalt all have different minerals
and therefore, groundwater in contact with these materi-

I. B. IJEH, I. E. UDOINYANG 721
Figure 8. Spatial variation of turbidity in the study area.
als will have different compositions. Acidic waters are
typically low in buffering calcium minerals, but are high
in dissolved carbon dioxide gas, which can cause the low
pH or acidity. Calcite neutralizer tanks with natural
crushed and screened pure calcium carbonate easily neu-
tralize acidic water from 6.0 to 6.9. Below 6.0 a blend of
calcite and Corosex is recommended. Common systems
used to treat low pH include Calcite Neutralizer, calcite
and Corosex Blend Neutralizer, pflow Neutrilizer, Soda
Ash Feed Pump Injection System. In neutralizer filters,
acidic waters slowly dissolve the calcium and magne-
sium media on contact as the water flows through the
filter, raising the pH of the water and increasing the alka-
linity. This eliminates the effects of corrosive water
chemistries and can help to prevent corrosion of piping
and fixtures. Generally the lower the pH, the lower the
hardness and alkalinity, and the higher the total dissolved
solids will mean the water is more corrosive. Further
studies can be undertaken to determine the amount and
type of trace minerals present in the groundwater.
5. Acknowledgements
The authors are grateful to the Imo State Rural Water
Supply Agency and UNICEF Owerri for giving us access
to their information resources. Special thanks to Mr B. I.
Nwaonu and Mr. R. N. Ibe of the Ministry of Public
Utilities, Owerri for their assistance.
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