UNEP/UNESCO/UNCH/ECA
URBAN POLLUTION OF SURFICIAL AND
GROUNDWATER AQUIFERS VULNERABILITY IN
AFRICA
EARLY WARNING REPORT FOR KETA
SHALLOW AQUIFER
Dr. Bruce Banoeng-Yakubo
National Coordinator
Geology Department.
University of Ghana
ORDER OF PRESENTATION
 INTRODUCTION
 RESULTS
 HYDROGEOLOGICAL CONDITIONS
 ACTIVITIES
 CONCLUTIONS
Map of souteastern Ghana showing insert of the geology of the Keta basin
N
BEGORO
ATIMPOKU
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AKATSI
SOMANYA
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DENU
#
ADIDOME
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#
#
#
KOFORIDUA
#
SOGAKOPE
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#
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NSAWAM
DODOW A
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ADA FOAH
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Keta
LEGEND
AMASAMAN
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R oad s .s h p
To w ns
W a te r bo die s
M ap of s ou t hea s te rn G ha na s ho w ing an in s ert of pa rt o f t h e Ke ta b as in
Ac id & Bas i c G ne is s & Sc h is ts
M arin e Se rie s O f Sh ., Ss . & L m s t
R ed C o nt . D e p. O f Lim o nit ic S and S an dy C
U nc on s o. San d, C lay & G rav e l
W a te rb _bo dy . s hp
Vol ta _lk . s hp
C ont ou r1 .s h p
R iv ers p .s h p
M ars h p. s hp
Ele v at ion .s h p
C ont ou rs p. s h p
C ont ou r. s hp
C lipb ou nd. s hp
Bou nd .s h p
Ann ua l_ra in. s h p
TEMA MUNICIPAL AREA
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#
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ACCRA
50
0
50
100 Kilometers
OBJECTIVES OF STUDY
 assess the groundwater vulnerability in a selected urban
community
 identify hot spots and major threats on these aquifers in the
selected area
 develop policy options for better safeguarding surficial and
groundwater aquifers in the area, including pollution and health
mitigation.

 establish an early warning network for possible water supply
contamination
HYDROGEOLOGICAL CONDITIONS
 The Keta-Anloga area is underlain by recent unconsolidated
beach sands and lagoon clays, which deepen westwards
towards the Volta river estuary.
 The recent deposits rest on a series of continental beds of
Middle Tertiary age. The rocks are unconsolidated limonitic
argillaceous sands and gritty sands with persistent gravelly beds
at their base. The gravelly beds are persistent from the GhanaTogo border and they are about 2 m thick.
 The Middle Tertiary rocks have very permeable soils and
subsoils resulting in low run-off as a greater part of the rainfall
infiltrate into them and percolate into the groundwater
Geological map of the Keta Basin showing the Project area
11
HAVE (tk20)
'
'
)SASIAME(k38)
6
6
66
ACHAUE (k40)
N
'
'
AGAVEDZI (k23)
TSIAME (k34) ANYAKO (k18)
'
'
'
BLEKUSU (k24,A,28)
'
KEDZI (k17)
'
ATIAVE (k32,32a)
VODZA (k26)
'
'
KETA (k21,26,50)
######'
ket 18 #
##
##
####
#
kk3 #
###
#
###
kk21####
##
##
########
kk30##
# #
#
kk39 ## #
##
DN 3## # #
# ##
# ## # #
# #
#
TG 1## TG 2
# ##
TG 4#
# #
#
#
10
# # TG
# # #
#
ALAKPLE (prop/bh.)
'
ATITO(prop/bh.)
'
WOE (k48)
'
Marsh land
Towns
Area of current sampling
Keta Lagoon
#
Sampling points
#
Ketaboys34.dbf
Geologyp.shp
Acid & Basic Gneiss & Schists
Marine Series Of Sh.,Ss.& Lmst
Red Cont. Dep. Of Limonitic Sand Sandy C
Unconso. Sand, Clay & Gravel
#
Gh_dist_cap.shp
#
Ketapoint.shp
'
ANLOGA (k39)
'
10
0
10
20 Kilometers
11
The project for Ghana started late so the first
sampling was done in June 2002. This covered as
many sampling points as 106 in order to enable us
identify the wells to monitor. Subsequently, these
were reduced to 52. Four measurement campaigns
were undertaken within the period from mid-June to
September 2002. The monitoring was concentrated
on the shallow aquifer. This report is based on the
results of these four measurement campaigns.
Selection of Survey
Four main zones were established in the study area
and sampling was done at these four zone. These
zones are: Keta, Kedzikorfe, Dzelekorfe-Norlivime
and Tegbi. For simplicity, the following abbreviations
have been made:
KET denotes the Keta area;
KK denotes Kedzikorfe,
DN denotes Dzelekope-Norlivemi and
TG stands for Tegbi.
CLIMATE





 The study area lies within the Dry Equatorial Climatic region of
Ghana. This region is the driest in the country.

It has two clearly defined seasons; a rainy season and a dry
season. The rainy season exhibits double maxima, the main
occurring between April and June and the minor one between
September and October. June is normally the wettest month.

In general, the relative humidity is high in the mornings and at
night but is at a minimum in the afternoon. Instantaneous values
as high as 96% and as low as 63% have been recorded the
morning and afternoon respectively.

The mean annual rainfall for Keta based on data spanning the
period from 1913 to 1992 was 800.8mm. The highest mean
monthly value of 187.5mm occurs in June while the minimum
mean monthly value of 10.6mm occurs in January.

Annual potential evaporation of rate of 1785 mm/annum. This
figure is high compared to the annual precipitation figure. On a
monthly basis, it is only in June that rainfall exceeds potential
evaporation .
Figure 1. Distribution of Mean Monthly Rainfall and Pan
Evaporation in the Keta Area
Mean Monthly Rainfall &
Pan Evaporation (mm)
200
1 80
1 60
1 40
1 20
1 00
80
60
40
20
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Time (Months)
M o nthly Rainfall (mm)
M o nthly P an Evapo ratio n (mm)
Nov
Dec
WATER LEVEL VARIATIONS
The water level variation is presented for Tegbi area.
From the graph shown in Figure, the following was
observed:
 there was a general rise in water level from June
through August to September. However, in a few
cases, water level fell within the period in question.
Because most of the wells are in use, some of the
observations are a function of water use just before
sampling. It is believed that the monitoring period
(June to September) was too short to observe any
trends in the piezometric level.
Figure 3. Variation in Piezometric Level at Tegbi in the Study Area
Figure 2. Variation in Piezometric Level at Tegbi in the Study Area
2.5
2. 5
Water Level (m)
2
1.5
1
T G1
T G1
T G2
1 .5
T G3
T G2
T G6
1
T G7
T G3
T G8
T G1 0
0. 5
T G1 1
T G6
T G7
T G1 2
11-Sep -02
1-Sep-02
22-Aug -02
12-Aug -02
2-Aug-02
23-Jul-02
13-Jul-02
3-Jul-02
23-Jun-0 2
0.5
T G1 3
13-Jun-0 2
3-Jun-02
0
T G1 7
T G1 8
T G10
T G11
T G12
11-Sep -02
1-Sep-02
22-Aug -02
T G13
12-Aug -02
2-Aug-02
13-Ju l- 02
3-Jul- 02
23-Ju n-0 2
13-Ju n-0 2
23-Ju l- 02
Date
T G8
T G1 6
Date
0
3-Jun -02
Water Level (m)
2
T G16
T G17
T G18
VARIATION OF pH AND CONDUCTIVITY
 At the peak of the rainy season, the pH was high at
all sampling points except one. During the second
campaign, the pH value had dropped in almost all the
sampling stations under consideration.
 This second campaign was towards the end of the
major rainy season. There was a general rise in the
pH again during the third campaign, but this was more
noticeable for three stations namely DN2, D10 and
DN11

Between the third and fourth campaigns, the
variation in pH was less noticeable except for one
station (DN10) that exhibited a clear reduction. The
changes in pH values over the measurement period
ranged from a low of 6.6 to a high of 7.6.
5.1
Variation in pH
pH
Figure 3. Variation in pH with Time at Selected Sites in Study Area
8
7.8
7.6
7.4
7.2
7
6.8
6.6
6.4
6.2
6
DN2
DN4
DN6
DN9
Dn10
2
-0
ep
-S
2
11
-0
ep
-S
2
01
-0
ug
-A
2
22
-0
ug
-A
2
12
-0
ug
-A
02
2
-0
ul
-J
23
2
-0
ul
-J
13
2
-0
ul
-J
03
2
-0
un
-J
23
2
-0
un
-J
13
2
-0
un
-J
03
Time
DN11
DN16
VARIATION OF CONDUCTIVITY
 There is high variation of conductivity spatially. The
water conductivities of the aquifer towards Keta and
close to the lagoon and sea are very high and relates to
the high salinity recorded in these areas. Most of these
areas are less than 2m above sea level.

However, intensive agricultural practices especially
pumping of water to irrigate vegetables and other food
crops have rendered the aquifer system vulnerable to
saltwater intrusion.
Conductivity variations in Parts of the Keta area
#
S
# #
#######
# #
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Keta
ket 18
kk3
KEDZEKOPE
kk21 ABUTSIAKOPE
kk30
LEGEND
kk39
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####
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% # ##
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#
# %
## #
# # ##
# ###
#
#
#
#
#
#
#
#
#
#
#
#
#
DZELUKOPE
#
#
%
#
DN 3VUI
#
#
%
##
#
#
%
#
#
%
#
#
#
DEREKEHEKPA
#
%
%
TG 1
#
#
TG 2AGBADATOR
%
DZIAKPOR
#
#
TG 4
#
%
#
%
%
#
AFEDOMETEGBI
%
#
KPOKPE
#
%
KLAMATSI WOGONA
#
Roadsp.shp
Tow ns
Marsh land
#
Sam pling points
Map of conductivity distribution in the Keta Basin
< 500
500 - 1000
1000 - 1500
1500 - 2000
2000 - 2500
> 2500
#
Ketantowns.shp
Keta Lagoon
Ketangeology.shp
Red Cont. Dep. Of Limonitic Sand Sandy C
Unconso. Sand, Clay & Gravel
#
Ketaboys34.dbf
%
TETEVIKOPE
#
DUDU
#
TGAELEGLOKOPE
10
%
#
#
3
#
%
#
0
#
#
3 Kilometers
FFLUORIDE
CONCENTRATION
AND
CHLORIDE
 In general, the level of Fluoride in the water
samples are higher than the recommended 1.0
mg/l for drinking water. The mean value was 1mg/l
for the zone under consideration.
 Chloride levels in the water varied from below
2000mg/l to over 12,000 mg/l. Clearly the range
for drinking water is far below the values obtained
in this study. These values and their spatial
distribution
compare
favourably
with
the
conductivity measurements discussed in Figure.
ke
ke t 1
ke t 2
ke t 3
ke t 4
ke t 5
ke t 6
ke t 7
k t8
kee t 9
ke t 1 0
ke t 1 1
ke t 1 2
ke t 1 3
ke t 1 4
ke t 1 5
ke t 1 6
ke t 1 7
ke t 1 8
ke t 1 9
ke t 2 0
t
ke ke 2 1
t
ke t 2 322
t 2 -S
4S
Fluoride (mg/l)
25
20
10000
15
8000
10
6000
5
4000
2000
0
0
Location
Chloride (mg/l)
Figure 5. Fluoride and Choride Variation in Space at Keta (Date:
13/06/02)
14000
12000
Cl-
F-
VARIATION IN NITRATE CONCENTRATION IN
STUDY AREA
 Nitrate concentration in the study area is discussed
using results from the Keta zone. In this zone, the
concentration of nitrate varied between 0 and 251
mg/l.
 In general the nitrate concentration decreased
between June and August. This may be attributed to
the fact that in June, runoff carried a lot of nitrate from
farms and other areas in to the shallow aquifer.
VARIATION IN NITRATE CONCENTRATION IN STUDY AREA
Figure 6. Variation in Nitrate Concentration in Study Area
250
KET1
KET4
200
KET5
KET8
150
KET10
KET12
100
KET14
KET16
KET17
50
KET18
KET20
Date
11-Sep -02
1- Sep- 02
22-Aug -02
12-Aug -02
2- Aug- 02
23-Jul-02
13-Jul-02
3- Jul-02
23-Jun-0 2
13-Jun-0 2
0
3- Jun-02
Nitrate Concentration (mg/l)
300
Nitrate concentration distribution in the keta area
VODZA
#
N
ADZIDZE
#
Keta
#
##### ###
#
##
#
#
#
# ###
#
#
# ##
#
## #
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#
#
#
# ### #
# # ##
#
# ##
#
#
#
#
#
#
#
#
#
#
ABUTSIAKOPE
# #
#
DZELUKOPE
# #
#
#
#
#
#
#
VUI
#
#
TETEVIKOPE
#
##
#
#
#
#
#
#
HEKPA
#
DEREKE
#
#
# #
3
0
Keta Lagoon
Setllement.shp
Road
Nitrate concentration distribution in the Keta area
0 - 10
10 - 20
20 - 30
30 - 40
40 - 50
50 - 60
60 - 70
70 - 80
80 - 90
90 - 100
100 - 110
110 - 120
120 - 130
130 - 140
140 - 150
150 - 160
160 - 170
170 - 180
180 - 190
190 - 200
Geologyp.shp
Acid & Basic Gneiss & Schists
Marine Series Of Sh.,Ss.& Lmst
Red Cont. Dep. Of Limonitic Sand Sandy C
Unconso. Sand, Clay & Gravel
Bound_line.shp
# Unesco-keta corrected.txt
#
KEDZEKOPE
#
## #
#
LEGEND
AGBADATOR
3
#
#
#
#
6 Kilometers
8.0
BACTERIOLOGICAL ANALYSIS
The bacteriological analysis was carried out for 16
shallow wells in the study area. The samples were taken
on 28th September 2002. All necessary precautions
were taken to preserve sample quality until the analysis
were carried out within 24 hours of sampling. The
results are presented in table below and illustrated in the
following figure .
Figure 8. Bacteriological Quality of Selected Wells in Study Area
2000
Bacterial Count
1 800
1 600
1 400
1 200
1 000
800
600
400
200
0
KE
KK
KK
KK
7
T1
29
17
33
10
T3
N
16
9
N
KE
D
D
KK
2
6
T1
N
KE
D
17
TG
9
T6
N
KE
D
39
37
3
TG
KK
KK
Station
9

Nitrate
CONCLUSIONS.
(NO3)
, Ammonium and Phosphate
concentrations were all high, exceeding the WHO guide line
values
for
drinking
water.

The same observation was made for Fluoride and
Chloride concentrations. In general, conductivity was
also above the WHO guideline values for drinking water
for
most
of
the
locations.
Fluoride and Chloride concentrations in the Keta area
show that both are above the WHO recommended limits
for drinking water with mean values of 1mg/l and
999mg/lrespectively.

The bacteriological quality of the water was bad,
presenting both total and feacal coliforms in very high
PERSPECTIVES
 It is clear that the Keta-Anloga area is very polluted. The main
thrust of subsequent sampling will be to identify the actual
pollution areas apart from salinity from both the sea and the
lagoon
 To delineate the freshwater-saline interfaces in order to
establish monitoring points along them.
 To consolidate the monitoring process in order to determine long
term trends and to also establish a network of monitoring wells
in the Anloga area where irrigation and the use of manure and
fertilizer is intensive.
 To disseminate our findings through the District Assembly and
Community Water and Sanitation Agency and EPA that will
provide a platform for public discussion.
Table 1. Variation in Piezometric Water Level With Time
Station No.
TG1
TG2
TG3
TG6
TG7
TG8
TG10
TG11
TG12
TG13
TG16
TG17
Static water level (m)
0.78
1.36
0.69
0.89
0.84
0.70
0.70
0.48
0.52
2.38
0.88
0.73
Table 2. Variation in pH with Time and Location at Dzelekorfe-Norlivime
Station
DN2
DN4
DN6
DN9
DN10
DN11
DN12
DN14
DN16
pH
7.21
6.91
7.64
7.42
7.49
7.32
7.29
7.34
7.43
Table 3 Variation in Conductivity with Time and Location at Tegbi
Location/Date 15-June 02
TG1
TG2
TG3
TG6
TG7
TG8
TG10
TG11
TG12
TG13
TG16
TG17
TG18
31Jul-02
14160
719
1093
3360
808
1228
3710
744
438
8960
1828
602
15Aug 02
4-Sept-02
15180
593
1079
3550
783
1236
3460
654
433
7140
1739
659
383
155501
776
1059
3800
786
1237
3360
741
443
6630
1706
591
361
Table 4. Fluoride and Chloride Concentrations in Shallow Aquifers in mg/l
Location/Date 15-June 02
31Jul-02
15Aug 02
4-Sept-02
TG1
0.66
0.88
0.42
TG2
8.78
0
0
TG3
21.28
0
1.36
TG6
TG7
TG8
TG10
TG11
20.58
17.78
0
0
20.08
0
0.22
0
0.2
0.14
14.02
0.98
0.68
0
0
17300
Table 5. Variation in Nitrate concentration at Keta Area
Location/date 15-June 02
31Jul-02
Ket1
19.14
38.24
36.14
32.40
251.1
46.34
54.16
0
79.72
79.78
Ket4
Ket5
Ket6
Ket8
Ket10
Ket12
Ket14
Ket16
Ket17
Ket18
Ket20
96.12
14.78
0
103.34
19.78
22.16
139.78
130.04
13.7
16.42
53.0
62.84
5.3
15Aug 02
4-Sept-02
53.32
43.62
53.9
20.04
24.34
37.9
57.76
40.42
79.56
51.28
167.28
151.1
2.52
9.28
19.24
19.56
153.04
143.92
3.94
46.42
37.16
53.6
1.66
1.0
Table 7 Distribution of Number of Bacteriological Species by Sampling Stations
Station No.
Number of Bacteriological Counts
KK37
550
KK39
130
TG3
50
DN9
1800
KET6
1600
TG17
1800
DN2
1600
KET16
1800
KK9
130
DN16
425
DN10
900
KET3
1800
KK33
1800
KK17
1600
KK29
550
KET17
1600