i
HYDROCHEMICAL CHARACTERISTICS AND QUALITY
ASSESSMENT OF GROUNDWATER IN WARRI,
SOUTH SOUTH NIGERIA
BY
ISRAEL GODWIN OMANUDHOWHO
PG/M.SC/07/43369
A RESEARCH PROJECT SUBMITTED TO THE
DEPARTMENT OF GEOLOGY, FACULTY OF PHYSICAL
SCIENCES
UNIVERSITY OF NIGERIA, NSUKKA
IN PARTIAL FULLFILMENT OF THE REQUIREMENT
FOR THE AWARD OF A MASTER OF SCIENCE IN
GEOLOGY (HYDROGEOLOGY)
NOVEMBER, 2012.
ii
CERTIFICATION
Israel, Godwin Omanudhowho is a postgraduate student in the Department of Geology with
the registration number PG/M.SC/07/43369 has satisfactorily completed the requirements for
the course and research work for the degree of Master of Science in Hydreogeology.
The work embodied in this project report is original and has not been submitted in part or full
for any degree or diploma of this or any other university.
…………………… ……………………..
Prof. C. O. Okogbue Date
Project Supervisor
Prof. O.P. Umeji ……………………….
Head of Department Date
External Examiner ………………………….
Date
iii
DEDICATION
This paper is dedicated to God Almighty who gave me the direction.
iv
ACKNOWLEDGEMENT
I would like to thank my supervisor, Prof. C.O. Okogbue for taking out some time out of his
busy schedule to read through this thesis. The quality of this work is consequent upon his
criticisms, corrections and suggestions.
I will not forget the efforts of my former supervisor, Prof H.I Ezeigbo, who has gone to meet
with the Lord, may his gentle soul rest in peace.
I am particularly grateful to Mr. S.O. Onwuka for his immense contribution the success of
this project.
My profound gratitude goes to all members of staff of the Department of Geology, University
of Nigeria, Nsukka, for providing a good working environment.
I am grateful to my beloved wife, Mrs. Blessing Israel and children, Ujiro, Ewomazino and
Iruo-Oghene Israel for their support and understanding while this write up lasted.
I will not fail to appreciate the efforts of Dr S.O Olobaniyi of the Department of Geology,
Delta State University Abraka for critical review and discussion on the paper.
I am grateful to Engineer P. Awala of Delta State Water Board for providing some useful
materials for this write up.
I equally recognize the contributions of my fellow researchers, Mr. Victor Omonona, Mr.
Rufai Ayuba, Mr. Ezekiel Agberen and Miss Joseph Mary. You are all wonderful.
Finally to my spiritual fathers, Bishop Chris Okoh and Reverend Emmanuel Afor who have
been praying for the successful completion of this project, I say thank you.
.
v
ABSTRACT
The physicochemical characteristics and quality of the shallow groundwater of the Warri
coastal aquifer were studied by means of chemical composition (groundwater chemistry) and
ionic ratios. Twenty groundwater samples were collected from hand dug wells and analyzed
for major cations like Ca2+
, Mg2+
, K+ and Na
+, anions like SO
2-4, HCO
-3 NO
-3 and Cl
-; heavy
metals like Pb2+
Ni2+
and Cd2+
. Results of the analysis revealed that rock weathering and
anthropogenic processes are the major contributors to the chemical compositions of the
groundwater. They also showed that groundwater is affected by seawater intrusion as it
featured high levels of chloride (Cl) and total dissolved solids (TDS) which are common
indicators of seawater influence. The groundwater classified into three water types namely,
Ca(HCO3)2, CaCl2 and NaCl water types. Among the physiochemical parameters measured
(pH, EC, TDS, TH, fecal coliform, total bacterial, SO4, Cl, HCO3, NO3, Ca, Mg, Na, K, Pb,
Ni, Cd) only nitrate (NO3), sulphate (SO4) and total bacteria (Bac.) have concentrations
below the stipulated WHO (1993) guideline values, indicating that the groundwater of the
area is not suitable as drinking water. It was demonstrated that ionic ratios such as HCO3/Cl,
Ca/Mg, Ca/Cl and Ca/SO4 are useful indices to identify seawater intrusion in the area.
vi
TABLE OF CONTENT
TITLE PAGE i
CERTIFICATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
TABLE OF CONTENT vi
LIST OF TABLES vii
LIST OF FIGURES viii
LIST OF APPENDICES x
CHAPTER ONE: INTRODUCTION
1:1 Background of the study 1
1.2. Aims of Study 1
1.3. Location and Accessibility 2
1.4 Relief and Drainage 2
1.5 Climate and Vegetation 2
1.6 Literature Review. 6
CHAPTER TWO: GEOLOGY AND HYDROGEOLOGY
2.1 The Geology of the Niger Delta 8
2.2 Local Geology 10
2.3 Hydrogeology of Warri 11
CHAPTER THREE: RESEARCH METHODOLOGY
3.1 Hydro-geological Investigation 13
3.2 Hydro geochemical Investigation 13
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 Groundwater Chemistry 14
vii
4.2 Groundwater Type 14
4.3 Sources of Ions 26
4.4 Groundwater Quality for Drinking Purposes 26
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATIONS
5.1 Conclusions 31
5.2 Recommendation 31
REFERENCES 32
APPENDICES 37
viii
LIST OF TABLES
Table 1 Physico-chemical and bacteriological content values of the shallow
groundwater in Warri coastal area 17
Table 2: Groundwater classification based on total hardness (TH) 18
Table 3: Ionic ratios and ionic strength of the shallow groundwater in
Warri coastal area 21
Table 4: Ground water indexes and WHO (1993) Stipulated guideline values 30
ix
LIST OF FIGURES
Figure 1: Satellite image of Warri 3
Figure 2: Location Map of Warri City showing Groundwater Samples Point 4
Figure 3: Map of the Niger Delta Showing the Drainage system 5
Figure4: Geological map of parts of the western Niger Delta 9
Figure 5: Piper Diagram showing the water types and mixing line 19
Figure 6: Spatial Distributions of Groundwater Types 20
Figure 7:Cumulative Frequency Percentage Plots 22
Figure 8: Bivariate plot of Cl and TDS concentrations 23
Figure 9: Ionic ratios of some chemical parameters of groundwater samples, dotted
lines represent ionic ratio of chemical parameters of seawater samples 24
Figure 10: Gibbs Diagram (A-anionic and B-cationic) showing the groundwater
chemical composition controlling processes 27
Figure\11: Stiff Pattern Diagram of groundwater samples showing variation
in chemical compositions in various groundwater samples 28
x
APPENDICES
1. WELL DATA OF WARRI CITY 37
2. LITHOLOGICAL LOGS OF PARTS OF WARRI CITY 38
1
CHAPTER ONE
GENERAL INTRODUCTION
1.1 Background of the study
Water is perhaps the most essential of all natural resources because it is fundamental to all
vital processes of mankind. The quantitative supply of water can be a local issue, but in many
regions the most serious problem hindering the utilization of water resources is the
deterioration of water caused by pollution, which leads to an estimated 25,000 deaths daily
because of water – related sicknesses (United Nations Population Information Network,
Popin1994). Deficient water supplies and sanitation therefore pose the most serious
environmental problems that face developing countries today. Ayoade and Oyebande (1973)
noted that less than 30% of Nigerian cities are served by public water schemes. This fact
remains true and is evident in Warri and its environs where private wells and boreholes
ownership are common.
Warri is a coastal town located strategically in the Niger Delta area of Nigeria and it is an
operational base for many of the oil producing and servicing companies. Its population is
estimated to be over a million people. Potable water supply in the town both from the
government agency (State public water utilities board), parastatals and individuals is
predominantly from groundwater. In Warri town and its environs, rapid urbanization and
industrialization are ongoing, which implies an increase in the generation of domestic and
industrial wastes, preponderance of individual septic tanks, indiscriminate drilling of
boreholes with its attendant over–abstraction problems that enhance pollutant concentrations
and saline water intrusion of the groundwater resources. Therefore, periodic examination to
ascertain the quality of the groundwater is indispensable. The fact that most of the water
consumed does not undergo treatment by the state public water utilities makes it pertinent to
regularly conduct and monitor physical, chemical and biological analysis.
1.2 Aims of Study
The aims of this study include:
I. To examine the physio-chemical and biological attributes of groundwater from the Deltaic
Plain Sands aquifer underlying Warri town and its environs.
II. To determine the suitability of the groundwater resources for drinking and domestic uses.
2
1.3 Location and Accessibility
Warri is located between latitudes 50 30′ and 5
035′ N `and longitudes 5
0 29′ and 5
0 48′ E. It is
within the oil rich province of Nigeria, some 50 km away from the shores of the Atlantic
Ocean. It occupies a low- lying area with a mean height of 6m above sea level. It is a flat land
with very gentle slope towards River Warri and its tributaries that empty their water into the
Atlantic Ocean as shown by Warri satellite image (Fig 1).Warri town has two main entry
points; one from Benin in Edo State and the other from Port Harcourt in Rivers State. Also,
the numerous networks of roads from Effurun area to Warri- Sapele road through
NPA/NNPC express way (Fig.2) make the town easily accessible for groundwater sampling.
1.4 Relief and Drainage
The study area is low-lying with mean height of 6m above sea level. The area is drained by
River Warri and its network of tributaries and creeks, which empty into the sea (Fig. 3). River
Warri has an extensive flood plain and a dendritic drainage pattern with tributaries branching
without a preferred orientation. This signifies a homogenous underlying material where
structural control is lacking. The River is perennial partly because of high precipitation
resulting from the humid tropical climate and it is also tide influenced. As a result of
freshwater-saltwater mixture, a brackish environment is created at the banks of the river and
associated creeks. Consequently, vegetation along the river banks is made up of mangrove
plants of different species (Olobaniyi and Owoyemi, 2006).
1.5 Climate and Vegetation
The climate of the area is the tropical equatorial type dominated by two seasons, a long wet
season (April to October) and a shot dry season (November to March), in response to the
interplay between the southwest and the northeast trade winds that blow over Nigeria. Annual
rainfall is usually in excess of 3000mm, as no month of the year is entirely devoid of rainfall.
Temperature is above 280C and humidity is about 80% (Iloeje 1981). The vegetation is
dominated by mangrove swamp forest, although further inland, it becomes rainforest. This
natural vegetation setting has been extensively altered by human activities such as farming
and lumbering and in many cases, has been replaced by grassland.
3
Figure 1: Satellite image of Warri (source: Google Imagery, 2011)
4
Figure 2: Location Map of Warri City showing Groundwater Samples Point
5
Figure 3: Map of the Niger Delta Showing the Drainage system (Inger, et at., 2005)
6
1.6 Literature Review.
A good number of hydrogeophysical and hydrogeochemical works have been carried out in
the Niger Delta region, of which the study area belongs. Netherlands Engineering Consultant,
(1961) reported average salinity at sea and land boundary gradient to range from 5000 to
10,000ppm in the Niger Delta. Etu – Efeotor, (1981) showed the saline /freshwater interface
to be up to 60 to 80km inland far north of PortHarcourt. Oteri, (1983) carried out electric log
to determine the various depths to fresh water in the western Niger Delta and reported that the
area experiences varying degrees of saltwater intrusion. Amajor, (1986) detailed the
geochemical characteristics of groundwater in Port Harcourt and its environs and found that
the groundwater in the area is enriched with Na+, Ca
2+ ,Mg
2+,Cl
-, HC03 and S04
2-. Amajor
and Ofoegbu, (1988) found fluoride concentrations of 0.2mg/l in groundwater from the
eastern Niger Delta. Oteri, (1988) evaluated saltwater intrusion in the eastern Niger Delta.
Amadi, et al, (1989) found total iron concentration up to 6.2mg/l in the groundwater from the
Niger Delta. Edet, (1993) carried out a detailed groundwater quality assessment in parts of
the eastern Niger Delta and found an increase in Cl- and decrease in HC03
- content towards
the coast indicating saltwater encroachment. Akpokodje, (1999) noted that a staggering
amount of solid waste is generated in the Port Harcourt metropolis each year. Udom et al.
(1999) studied the hydrogeochemical evaluation of groundwater in parts of Port Harcourt and
Tai Eleme Local Government Areas and discovered that the groundwater in the Benin
Formation is soft and low in dissolved constituents except pH and iron with mean values of
6.01 and 0.36 mg/l respectively Akpoborie, et al, (2000) examined the quality of groundwater
from dug wells in Ughelli, Warri, and Okurekpo all in Delta State and reported low values of
pH and high amount of coliform bacterial in wells of the area. Efe, (2000) did an appraisal of
rain and groundwater resources in Warri and found that groundwater has higher values of pH,
TDS, EC, Ca2+
, Mg2+
, HC03- and Cl- while rain water is higher in Pb
2+, S04
2- and N03-.Edet
and Okereke, (2001) found groundwater with total dissolved solids (TDS) concentrations up
to 1250mg/l in the coastal part of the Niger Delta. Orisakwe, et al., (2001) documented the
distribution, migration and fate of micro pollutants in potable water of Warri and its environs.
Aremu, et al., (2002) linked high concentrations of iron, lead and nickel in dug-well water
from the Warri area to contamination from petroleum chemicals. Ogunkoya and Efi, (2003)
examined rainfall quality and sources of rainwater acidity in Warri area of the Niger Delta
and reported that the enormous gas flared into the atmosphere by the oil industries precipitate
acid rain in the area. Olobaniyi and Owoyemi, (2004) found a high coliform count in the
bacteriological determination of groundwater from the Deltaic Plain Sands aquifer underlying
Warri. Spiff and Horsfall, (2004) reported trace metal contamination of the intertidal flats of
7
the Upper New Calabar River in the Niger Delta. Udom and Esu, (2004) carried out a
preliminary assessment of the impact of solid wastes on soil and groundwater in Port
Harcourt city and it’s environ and concluded that the groundwater of that area is
contaminated. Efe et al., (2005) investigated the influence of seasons on the physico-
chemical characteristics of water in the western horn of the Niger Delta and observed fast
deteriorating levels of groundwater quality in the area due to human activity. Emoyan, et al.,
(2006) confirmed high levels of heavy metal contamination of River Ijana – an effluent
receiving stream that flows by Warri refinery. Olobaniyi and Owoyemi, (2006) discovered
that saltwater concentrations in the aquifer underlying Warri decrease away from the tidal
influenced Warri River. Olobaniyi and Efe, (2007) showed elevated levels of lead (0.56mg/l)
and low pH values ranging from 5.10 – 6.35 in rain water collected in Warri and environs.
John, et al., (2008) advocated for the monitoring of physico-chemical parameters of potable
water in Warri to ensure quality water supply to human health.
8
CHAPTER TWO
GEOLOGY AND HYDROGEOLOGY
2.1 The Geology of the Niger Delta
The Niger Delta Basin covers most areas of Rivers, Bayelsa, Edo and Delta States of Nigeria.
Its areal extent is about 75,000km2
and consists predominantly of Cretaceous to Recent
clastic sediment piles of about 8000m thick that rest unconformably on the sialic basement
complex. The Delta consists of broad riverine areas through which the River Niger enters the
Atlantic Ocean, dividing into numerous rivulets, which fan out into the sea. It also includes a
number of tidal creeks separating small islands of less than 10m above sea level (Offodile,
2002).
The geological sedimentary sequence of the Niger Delta is made up as follows:
The Ameki Formation, the Ogwash- Asaba Formation, the Benin Formation, and the
Somebreiro Deltaic Plains Sands (Fig 4).
9
Figure 4: Geological map of parts of the western Niger Delta (Modified from
Akpoborie, et al., 2011).
10
The Ameki Formation was deposited during the regression of the sea in early Eocene. Its
lower unit consists of fine to coarse sandstone with intercalations of calcareous shale and thin
limestone, while the upper unit consists of coarse cross-bedded sandstones and sandy clay
(Reyment, 1965).The Ogwashi-Asaba Formation (Miocene) overlies the Ameki Formation
and extends from just west of the Siluko River on the eastern flank in the Okitipupa area with
a steady widening outcrop towards Onitsha. The formation consists dominantly of clays,
sands, grits and seams of lignite alternating with gritty clays. Within the Ogwashi-Asaba
Formation, the lignites are confined to a narrow belt of about 16 km wide 241 km long
trending northwest-southeast from the Niger in the west of the Nigeria-Cameroun frontiers,
east of Calabar.The Benin Formation is Oligocene to Pleistocene in age. This formation
outcrops in the north east of the coastal belt in the Niger Delta and dips at a low angle in the
southwest. The sediments consist, generally, of lenticular unconsolidated, dominantly sandy
formations. Lenticular clays and shales occur particularly in the eastern areas where they
confine small but moderately high yielding aquifers. The 90-150m confining clay beds
encountered in the Niger Delta area, (Brass, Bonny and Opobo) disappear in the regions,
north of the area, and adjacent to the Benin Formation area (Bodo, Okrika and Port Harcourt)
(Offodile, 2002). The thickness of the Benin Formation is variable, but generally exceeds
2000m.The Somebreiro Deltaic Plains Sands is late Pleistocene to Holocene in age. It
occupies most of the area of the present delta and stretches narrowly eastwards along the
coastline. The sediments consist of medium to coarse –grained unconsolidated sands forming
lenticular beds with intercalation of peaty matter and lenses of soft silty clay and shale. These
beds dip at varying angles towards the sea, forming units, which represent series of old deltas
(Offodile, 2002). The gravelly beds of the formation could be up to 9m thick.
2.2 Local Geology
Warri town is underlain by a sequence of sedimentary formations with a thickness of about
8000metres, which include from bottom to top, the Akata Formation, the Agbada Formation,
the Benin Formation and the Somebreiro Warri Deltaic Plain Sands (Allen, 1965; Reyment,
1965; Short and Stauble, 1967).
The Akata Formation rests unconformably on the migmatite-gneiss basement complex and
forms the basal unit of the Niger Delta stratigraphic pile .This formation consists of an open
marine facies unit dominated by high-pressured carbonaceous shales. The formation ranges in
age from Paleocene to Eocene and its thickness could exceed 1000 meters. The Agbada
Formation consists of a sequence of alternating deltaic sands and shales. It is Eocene to
11
Oligocene in age and exceeds 3000 meters in thickness. This formation is the oil –reservoir in
the Niger Delta basin. The Benin Formation which is Oligocene to Pleistocene in age consists
essentially of massive and highly porous sands and gravels with a few thin clay
intercalations. Its uppermost section is the quaternary deposit which is about 40-150m thick
and comprises rapidly alternating sequences of sand and silt / clay with the later becoming
increasingly more prominent seawards (Etu – Efeotor and Akpokodje, 1990).The Benin
Formation houses the most productive and hence most tapped aquifer in the Niger Delta
region, especially in areas north of Warri where it is shallow. The thickness of the formation
is variable, but generally exceeds 2000m.
The Somebreiro-Warri Deltaic Plain Sand is Quaternary to Recent in age and directly
underlies the study area. It consists of fine to medium unconsolidated sands that are often
feldspathic (with 30-40 % wt feldspars) and occasionally gravely (Wigwe, 1975). The
sequence is locally stratified with peat and lenses of soft and plastic clay that could be sandy
and shally. It generally does not exceed 120m in thickness and is predominantly unconfined.
2.3 Hydrogeology of Warri
The hydrogeology of an area is usually controlled by such factors as geology and climate of
that area. This is because geological formations underlying an area and the structure
contained in them determine the types of aquifer to be encountered and how the aquifers are
recharged, while the climate determines the amount and the rate of recharge the aquifer
receives (Ariyo and Adeyemi, 2005). The study area is drained by River Warri, a major
navigable channel in the Niger Delta southern Nigeria. It takes its source from around Utagba
Uno and flows through zones of fresh water swamp, mangrove swamps and coastal ridges.
The river stretches within latitude 502
1N-6
000
1N and longitude 5
024
1E-6
021
1E, covering a
surface area of about 255 sq. km with a length of about 150km (Netherlands Engineering
Consultants, 1961). It drains various tributaries and empties into the brackish Forcados River
and in turn into the Atlantic Ocean.
Local hydrogeological setting indicates that Warri is underlain by the Somebreiro-Warri
Plain Sands aquifer which consists of fine to medium and coarse grained unconsolidated
sands, gravels and. shales. The aquifer in most cases unconfined, has thickness that ranges
from 60 to 95m and hydraulic conductivity that varies from 8.82 x 10-3
to 9.0 x 10-2
cm/s.
Specific capacities recorded from different locations outside Warri city where the unit has
been penetrated vary from 6700 lit/hr/m to 13500 lit/hr/m, (Ofodile, 2002).The water table is
very close to the ground surface and varies in depth from 2 to 4m. Low groundwater
12
fluctuation is reflection of the high amount of precipitation often recorded in the Warri area
over a greater part of the year.
13
CHAPTER THREE
RESEARCH METHODOLOGY
3.1 Hydro-geological Investigation
The hydrogeological investigation involved measurement of well diameters, static water level in
wells and depth to water table using tape meter. Topographic elevations of well locations above
mean sea level and geographical co-ordinates were measured with the GPS. Lithology logs
covering parts of the area and obtained from Delta State Water Board were examined to
authenticate the claims of other researchers about the nature and types of the aquifer.
3.2 Hydro geochemical Investigation
A total of twenty (20) groundwater samples from hand-dug wells within Warri city were
collected in two-liter plastic containers during the month of February. The depths of wells
measured ranged from 4.1m to 5.4m below ground level. Physical parameters (pH, temperature,
total dissolved solid (TDS) and electrical conductivity) were measured in the field by EC/TDS
meter, (Wissencheflich Technische Werkstetten (WTW) LF 91 model) while colour and turbidity
were determined with Hach DR/2000 spectrophotometer. Other parameters were determined in
the laboratory and included total hardness (TH) which was determined with Hach digital titrator,
sodium (Na+), calcium (Ca
2+), magnesium ( Mg
2+), potassium (K
+) and iron (Fe
2+) which were
analyzed using atomic absorption spectrophotometer (Perkin – Elemer AAS 3110), bicarbonate
(HCO-3), Chloride (Cl
-), nitrate (NO
-3) and sulphate (SO4
2-) which were analyzed using the
colorimetric method with UV spectrophotometer (WPAS110). Lead (Pb), Nickel (Ni), and
Cadmium (Cd) were determined with digital bulk 205 atomic absorption spectrophotometer
(AAS) while biological analyses (total bacteria and fecal coliform) were determined by multiple
tube fermentation technique.
14
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Groundwater Chemistry
The results of the physiochemical and biological analyses of the groundwater samples are
presented in Table 1. The pH value varies from 6.45 to 7.80 with an average of 7.03 which
reveals that the groundwater is slightly acidic to slightly alkaline. Total dissolved solids (TDS)
values ranged from 328mg/l to 857mg/l with a mean value of 492mg/l indicating that the
groundwater of the area is all of the fresh water type (Hem, 1970). Total hardness measured
ranged from 74mg/l to 328mg/l with an average of 198mg/l. Hardness classification of
groundwater (after Sawyer and McMcartly, 1967) reveals that the Warri groundwater falls into
the four categories, namely soft, moderately hard, hard and very hard with 5% of the samples
being soft, 15% moderately hard, 70% hard and 10% very hard (see Table 2). The relative
abundance of cations and anions is in the order; Ca2+
> Na+ > Mg
2+ > K
+ and Cl
- > HCO
-3 >.
SO42+
respectively. Calcium and chloride are the most dominant ions with average concentration
values of 3.063meq/l and 3.852meq/l respectively while potassium and sulphate have the least
average concentrations of 0.819 and 0.124meq/l respectively among the major ions.
4.2 Groundwater Type
The 20 groundwater samples analyzed were classified using the Piper diagram (Fig. 5). The ions
classified by the diagram are Ca2+
, Mg2+
, Na+, K
+, HCO3
-, Cl
- and SO4
-. Three groups of
groundwater types were observed namely: calcium bicarbonate (Ca(HCO3)2) water type, calcium
chloride (CaCl2) water type and sodium chloride (NaCl) water type. The Ca(HCO3)2 water type
reflects groundwater of recharge zone area that is characterized with low EC and TDS, while the
NaCl water type reflects groundwater of the discharge zone area that is generally characterized
with high EC and TDS. The CaCl2 water type is the transition zone between the two types. The
spatial distribution of the groundwater types is presented in figure 6 and reveals that the NaCl
water type is closer to the low lying sea shore while the CaHCO3 water type is confined to the
upland area. The presence of sodium chloride (NaCl) water type in the Warri area suggests
possible salinization of groundwater in the area. The possible sources of salinization were
investigated using the concentrations of the major ions and ionic ratios (see Table 3). Pulido-
15
Bosch, et al.,(1999), Sanchez-Martos, et al., (2000), Kim, et al., (2003b), Park, et al., (2005), El
Moujabber, et al., (2006), Lee and Song, (2007), and Nwankwoala and Udom, (2011) have all
shown that concentrations of major ions and ionic ratios can be used to decipher the contributing
sources of saline water in coastal aquifers. Figure 7 is the cumulative frequency percentage plots
of the major chemical constituents ( SO2-
4, Cl-, Ca
2+, Na
+, Mg
2+ and TDS) of the Warri city
groundwater. Only two threshold values those of ( Cl- and TDS) could be determined from the
figure as the mean value for the two groundwater threshold values for SO2-
4, Ca2+
, Mg2+
and Na+
could not be determined because of the difficulty in establishing a singular break in their plots
(see also Fig. 7). The threshold values for TDS and Cl (parameter indicators of salinization) are
724.44mg/l and 5.07meq/l respectively. Groundwater sample 6 that lies above the TDS threshold
line/value (724.4mg/l) and groundwater samples 1, 2, 3, 4, 5, 6 and 7 which lie above the Cl
threshold line/value (5.07meq/l) can be said to be salinitized by salt water intrusion. water
samples closest or nearest to the major break in the plots (see plots for TDS and Cl- in Fig. 7).
Threshold values for SO2-
4, Ca2+
, Mg2+
and Na+ could not be determined because of the
difficulty in establishing a singular break in their plots (see also fig. 7). The threshold values for
TDS and Cl (parameter indicators of salinization) are 724.44mg/l and 5.07meq/l respectively.
Groundwater sample 6 that lies above the TDS threshold line/value (724.4mg/l) and groundwater
samples 1, 2, 3, 4, 5, 6 and 7 which lie above the Cl threshold line/value (5.07meq/l) can be said
to be salinitized by salt water intrusion. However, bivariate plot of TDS and Cl concentrations
(Fig. 8) suggests that only groundwater sample 6 is affected by seawater intrusion implying that
cumulative frequency plots and bivariate plot are not enough to establish salinization of the
groundwater. Figure 9 is a plot of ionic ratios of Ca/Cl, Ca/Mg, HCO3/Cl and Ca/SO4 (ionic
ratios of the major ions) against TDS for groundwater samples that have correlation coefficients
greater 0.40 (correlation coefficient considered to be significant; values varied from 0.2 to 0.6)
and plotted very close to the seawater ratio line (see Fig.9). Only groundwater sample 6 which
has high TDS, Cl and SO4 (as revealed by low Ca/SO4 and Ca/Cl values) in all the four ionic
ratios plotted close to the sea water ratio line, implying that only this sample was influenced by
sea water intrusion. As groundwater of the NaHCO3 type does not exist in the study area, the
results imply that salinitization in the study area is caused mainly by recent sea water intrusion.
Mercado, (1985) and Sung-Work Jean, et al., (2000) had established that NaHCO3 water type
16
represents the partly flushed remains of an ancient entrapped saline water body. Its absence in
the study area implies that the sea water intrusion confirmed in sample 6 is a recent intrusion
17
Table 1: Physico-chemical and bacteriological content values of the shallow groundwater in
Warri coastal area LoLocati
onon
pH EC# TDS
α
THα Ba
c‡
Col
i+
SO4 Cl HC
O3
NO3 Ca Mg Na K
Fe Pb Ni Cd Water
type
1 7.02 850 516 150 3 0 0.089 5.53
3
1.8
39
0.20
1
1.1
79
1.2
32
4.00
0
0.4
31
0.2
2
0.0
1
0.0
06
0.001 NaCl
2 6.45 1010 520 152 6 0 0.105 5.67
3
2.5
59
0.20
1
1.4
00
1.1
05
4.00
0
0.3
44
0.2
4
0.0
1
0.0
21
0.001 NaCl
3 6.85 805 622 74 4 0 0.108 7.05
0
2.7
93
0.42
4
1.1
68
0.3
14
4.93
8
0.7
64
0.4
2
0.0
0
0.0
11
0.000 NaCl
4 7.50 1002 701 231 3 0 0.133 6.99
4
3.3
32
0.33
6
2.9
05
1.7
11
4.70
9
0.9
06
0.4
0
0.0
4
0.0
32
0.002 NaCl
5 6.72 920 707 154 5 1 0.142 6.75
1
3.9
70
0.56
1
1.2
49
1.8
44
3.92
4
1.1
97
0.4
2
0.0
3
0.0
40
0.003 NaCl
6 6.84 912 857 155 7 0 0.142 6.49
2
3.1
16
0.46
6
1.3
58
1.7
52
3.68
0
1.9
59
0.4
0
0.0
4
0.0
38
0.004 NaCl
7 6.62 790 613 114 6 3 0.140 6.06
4
3.5
53
0.48
4
1.0
38
1.2
43
1.98
5
1.6
22
0.3
4
0.0
2
0.0
28
0.004 NaCl
8 6.60 602 598 205 8 2 0.140 4.21
9
3.8
35
0.46
9
2.2
46
1.8
60
1.68
9
1.7
56
0.3
8
0.0
2
0.0
22
0.006 CaCl2
9 7.12 600 538 228 9 3 0.142 3.95
0
3.4
42
0.42
6
2.8
94
1.6
77
1.70
6
1.9
52
0.2
4
0.0
2
0.0
09
0.005 CaCl2
10 6.90 504 539 155 6 0 0.142 2.88
8
3.2
48
0.23
0
2.2
76
0.9
89
1.74
1
1.5
35
0.2
8
0.0
1
0.0
16
0.018 Ca(HC
O3)2
11 6.80 480 510 184 4 0 0.129 2.54
4
2.9
63
0.24
4
3.0
00
0.6
93
1.96
6
0.9
03
0.3
0
0.0
1
0.0
12
0.016 Ca(HC
O3)2
12 6.92 492 518 194 5 1 0.130 2.66
8
2.9
24
0.32
4
3.2
07
0.6
74
1.74
4
0.7
94
0.2
5
0.0
1
0.0
19
0.008 Ca(HC
O3)2
13 6.84 440 450 229 6 0 0.125 1.98
0
3.0
90
0.25
9
3.5
23
1.0
53
0.87
5
0.5
14
0.3
0
0.0
2
0.0
11
0.009 Ca(HC
O3)2
14 6.96 585 462 298 3 1 0.125 2.54
9
2.7
25
0.27
3
4.9
12
0.8
40
0.51
2
0.3
94
0.2
9
0.0
1
0.0
02
0.001 Ca(HC
O3)2
15 6.88 645 468 316 7 0 0.125 2.48
8
3.1
60
0.22
7
4.9
90
1.3
16
0.45
4
0.2
61
0.3
6
0.0
1
0.0
15
0.003 Ca(HC
O3)2
16 7.44 423 440 275 0 0 0.104 1.69
8
3.6
06
0.24
6
4.2
92
1.2
15
0.44
2
0.2
10
0.3
8
0.0
1
0.0
13
0.002 Ca(HC
O3)2
17 7.32 460 358 272 6 1 0.105 2.00
2
3.2
48
0.16
3
4.4
13
1.0
13
0.40
1
0.1
62
0.2
6
0.0
0
0.0
12
0.006 Ca(HC
O3)2
18 7.50 410 410 328 8 0 0.117 2.37
5
2.5
24
0.16
8
5.8
94
0.6
50
0.27
8
0.1
64
0.2
8
0.0
1
0.0
10
0.004 Ca(HC
O3)2
19 7.80 362 340 289 7 0 0.119 1.41
6
1.9
54
0.24
6
5.0
96
0.6
79
0.43
7
0.2
57
0.2
5
0.0
0
0.0
14
0.001 Ca(HC
O3)2
20 7.20 342 328 253 8 1 0.117 1.70
5
1.6
93
0.23
8
4.2
25
0.8
34
0.55
4
0.2
57
0.2
7
0.0
1
0.0
21
0.002 CaCl2
Mea
n
7.03 621 492 198 5.5 0.6
5
0.124 3.85
2
2.9
81
0.30
9
3.0
63
1.1
35
2.00
2
0.8
19
0.3
1
0.0
1
0.0
18
0.005
Sea* 8.10 53
n.a n.a n.a n.a 59.60 503.
6
1.8
44
n.a 21.
34
10
5.3
413.
2
9.9
76
n.a n.a n.a n.a
*values obtained from the off coast of Warri (n=2); #- µS/cm; α-mg/l; ‡-total bacteria
(/100ml);+-fecal coliform (/100ml), other parameters are measured in meq/l; n.a- not available
18
Table 2: Groundwater classification based on total hardness (TH) (after Sawyer and
McMcartly), 1967
Total hardness
(TH)
as CaCO3 (mg/l)
Water type Sample number Number of
Samples
Percentage of
samples (%)
<75 Soft 3 1 5
75-150 Moderately
hard 1, 2 and 7 3 15
150-300 Hard 4, 5, 6, 8, 9, 10, 11, 12, 13,14,
16, 17, 19 and 20
14 70
>300 Very hard 15 and 18 2 10
19
Figure 5: Piper Diagram showing the water types and mixing line
20
Figure 6: Spatial Distributions of Groundwater Types
21
Table 3: ionic ratios and ionic strength of the shallow groundwater in Warri coastal area
Na/Cl Ca/Cl SO4/Cl Ca/Mg Ca/HCO3 HCO3/Cl Na/Ca Ca/Cl Mg/Cl Ca/SO4 Mg/Ca Cl/HCO3 I.Sa
1 0.723 0.213 0.016 0.957 0.641 0.332 3.393 0.213 0.223 13.247 1.045 3.009 0.0084
2 0.705 0.247 0.019 1.267 0.547 0.451 2.857 0.247 0.195 13.333 0.789 2.217 0.0088
3 0.700 0.166 0.015 3.720 0.418 0.396 4.223 0.166 0.045 10.815 0.269 2.524 0.0093
4 0.673 0.415 0.019 1.698 0.872 0.476 1.621 0.415 0.245 21.842 0.589 2.099 0.0127
5 0.581 0.185 0.021 0.677 0.315 0.588 3.142 0.185 0.273 8.796 1.476 1.701 0.0111
6 0.567 0.209 0.022 0.775 0.436 0.480 2.710 0.209 0.270 9.563 1.290 2.083 0.0092
7 0.327 0.171 0.023 0.835 0.292 0.586 1.912 0.171 0.205 7.414 1.197 1.708 0.0089
8 0.398 0.529 0.033 1.208 0.641 0.849 0.752 0.532 0.438 16.043 0.828 1.100 0.0010
9 0.432 0.732 0.036 1.726 0.841 0.871 0.589 0.733 0.425 20.380 0.579 1.148 0.0085
10 0.603 0.788 0.049 2.301 0.701 1.125 0.765 0.788 0.342 16.028 0.435 0.889 0.0081
11 0.773 0.179 0.051 4.329 1.012 1.165 0.655 1.179 0.272 23.256 0.231 0.858 0.0080
12 0.654 1.202 0.049 4.758 1.097 1.096 0.544 1.202 0.253 24.669 0.210 0.912 0.0074
13 0.442 1.779 0.063 3.346 1.779 1.561 0.248 1.779 0.532 28.184 0.299 0.641 0.0079
14 0.201 1.927 0.049 5.848 1.803 1.069 0.104 1.927 0.330 39.296 0.171 0.935 0.0089
15 0.182 2.006 0.050 3.792 1.830 1.270 0.091 2.006 0.529 39.920 0.264 0.787 0.0095
16 0.260 2.528 0.061 3.533 1.190 2.124 0.103 2.528 0.716 41.269 0.283 0.471 0.0091
17 0.200 2.204 0.052 4.356 1.359 1.622 0.091 2.204 0.506 42.029 0.230 0.616 0.0084
18 0.117 2.482 0.049 9.068 2.335 1.063 0.047 2.482 0.274 50.376 0.110 0.941 0.0093
19 0.309 3.599 0.084 7.595 2.608 1.380 0.086 3.599 0.480 42.824 0.133 0.725 0.0079
20 0.325 2.478 0.069 5.066 2.496 0.993 0.131 2.478 0.489 36.111 0.197 1.007 0.0073
Mean
Seab 0.734 0.042 0.118 0.208 11.574 0.004 19.36 0.040 0.204 0.358 4.806 273.10 >0.005
a- Ionic strength; b-values of seawater obtained from the off coast of Warri (n=20)
22
Figure 7: Cumulative Frequency Percentage Plots for some chemical Constituents of Groundwater
23
Figure 8: Bivariate plot of Cl and TDS concentrations
24
Figure 9: Ionic ratios of some chemical parameters of groundwater samples, dotted lines
represent ionic ratio of chemical parameters of seawater samples
25
Figure 9: contd.
26
4.3 Sources of Ions
In order to evaluate the processes that control the chemical composition of groundwater from
Warri coastal area, the hydrochemical data of groundwater from the area were plotted in Gibbs
diagram (Fig. 10). The diagram reveals that groundwater chemistry or chemical composition is
controlled dominantly by rock weathering processes. The differences in concentrations of the
various ions in the groundwater as revealed by the Stiff diagram (Fig. 11) may be attributed to
the amounts of ions in the rock matrix, reaction characteristics and transport history.
4.4 Groundwater Quality for Drinking Purposes
Table 4 presents a comparison of the results of the biological and physiochemical analysis of
groundwater of the study area with the standard guideline values recommended by the World
Health organization (WHO, 1993) for drinking water purposes. It is observed from the Table
that 60% of the
samples show TDS values above the guideline value of 500mg/l. while 35%, 50% and 40% of
the samples are contaminated by the heavy metals of Pb, Cd and Ni respectively. Also, 40% and
30% of the groundwater samples have fecal coliform and Cl concentrations respectively above
the stipulated guideline values. All the groundwater samples, however, have total bacteria, SO2-
4
and NO-3 concentrations below guideline values for drinking water.
27
Figure 10: Gibbs Diagram (A-anionic and B-cationic) showing the groundwater chemical
composition controlling processes.
28
Figure 11: Stiff Pattern Diagram of groundwater samples showing variation in chemical
compositions in various groundwater samples.
29
Figure 11: contd.
30
Table 4: Ground water indices and WHO (1993) stipulated guideline values
Water quality Index
WHO (1993) guideline value
(mg/L)
Samples exceeding guideline values
Percentage of Samples exceeding guideline values
TDS 500 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 60 Total bacteria
a 10 nil 0 Fecal coliform
a 0 5, 7, 8, 9, 12, 14, 17, 20 40 SO4* 4.16 nil 0 Cl* 5.64 2, 3, 4, 5,6, 7 30 NO3* 0.73 nil 0 Pb 0.01 4, 5, 6, 7, 8, 9, 13 35 Cd 0.03 6, 7, 8, 9, 10, 11, 12, 13, 17, 18 50 Ni 0.03 1, 2, 3, 4, 5, 6, 7, 8 40
a-measured in /100ml; *measured in meq/l
31
CHAPTER FIVE
5.1 CONCLUSIONS
The chemical composition of the groundwater of the study area is strongly influenced by
weathering of the litho units of the rocks of the area along with anthropogenic activities.
Groundwaters of the area are slightly acidic to slightly alkaline in nature and also class as soft,
moderately hard, hard and very hard with about 70% of the water being hard.
Three groundwater types were recorded namely, calcium bicarbonate water type, calcium
chloride water type and sodium chloride water type with the sodium chloride type being closest
to the low-lying sea shore while the calcium bicarbonate type is confined to the upland area. The
calcium chloride type is in the transition zone.
Bivariate plot of TDS and Cl (parameter indicators of salt water intrusion) and ionic ratios of
Ca/Cl, Ca/Mg, HCO3/Cl and Ca/SO4 against TDS revealed that only one of the twenty
groundwater samples investigated had been influenced by salt water intrusion. Absence of
sodium bicarbonate water type which is indicative of partly flushed remains of ancient entrapped
saline water implied that the salt water intrusion recorded in the sample is that of recent intrusion
rather than being the flushed remains of ancient entrapped saline water.
Groundwater quality indices such as TDS, fecal coliform, Cl, Pb, Cd and Ni have concentrations
above the stipulated WHO (1993) guideline values, indicating that the groundwater of the area is
not suitable as drinking water.
5.2 RECOMMENDATION
It is hereby recommended that the centrally located waterworks scheme drilled into the Benin
Formation (205m) in the area should be empowered so as to discourage the indiscriminate
digging of hand dug wells and shallow boreholes into the shallow aquifer. Companies and
individuals under the supervision of Hydrogeologists are advised to sink their boreholes beyond
the Deltaic Plain Sand aquifer into the Benin Formation (>150m), so as to tap from the high
quality water of the formation devoid of bacteriological, heavy metals and saltwater
contaminations. In this current situation whereby some water samples are bacteriologically
32
contaminated, boiling and chlorination should also be carried out on such samples after
laboratory analysis so as to make the water fit for drinking.
33
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38
APPENDICES
APPENDIX 1:
WELL DATA
ND (not determined)
Sample
code
Well location Well
depth
(m)
SWL
(m)
Well
Diameter
(cm)
Ground
Elevation
(m)
Latitude Longitude
1 Warri GRA 4.6 1.0 80 6.0 50.32.2’N 5
033.5’E
2 Ajamimogha 4.8 1.1 80 6.6 5032.5’N 5
035.3’E
3 Edjeba 4.1 1.1 80 7.0 50.32.8’N 5
0.35.2’E
4 NNPC 1 4.7 1.3 60 7.8 50.34.1’N 5
0.35.4’E
5 NNPC 2 5.1 1.1 60 7.1 50.34.2’N 5
0.35.5’E
6 Refinery Rd ND ND ND ND 50.32.3’N 5
0.36.3;E
7 Ugboroke ND ND ND ND 50.32.5’N 5
0.35.2’E
8 Ok layout 5.2 7.1 60 7.1 50.32.4’N 5
0.35.6’E
9 Okere 4.9 1.1 80 6.1 50.32.5’N 5
0.35.6’E
10 Sokoh Estates 5.1 1.1 80 6.7 50.33.2’N 5
0.38.4’E
11 Effurun 5.4 1.2 60 6.9 50.33.5’N 5
0.38.8’E
12 Okuokoko 4.8 1.0 60 6.7 50.33.8’N 5
042.6’E
13 DSC Road 5.0 1.2 80 6.2 50.33.7’N 5
0.44.6’E
14 Enerhen 5.1 1.2 80 6.7 50.32.5’N 5
0.40.1’E
15 Ekete 4.6 1.1 80 6.1 50.31.5’N 5
0.40.3’E
16 Nmofor 4.8 1.2 80 6.6 50.33.5’N 5
0.44.2’E
17 Orhunwhorun 4.5 0.9 80 6.9 50.31.5’N 5
0.43.1’E
18 DSC Township 1 4.9 1.0 60 6.5 50.31.9’N 5
0.44.2’E
19 DSC Township 2 ND ND ND ND 50.30.2’N 5
0.45.7’E
20 Ovwian 5.1 1.1 80 6.6 50.31.4’N 5
0.39.2’E
39
APPENDIX 2: LITHOLOGICAL LOGS OF PARTS OF WARRI CITY