Water Policy Uncorrected Proof (2010) 1–12
Nitrate pollution in groundwater in two selected areas from
Cameroon and Chad in the Lake Chad basin
Benjamin Ngounou Ngatchaa and Djoret Dairab
Corresponding author. Department of Earth Sciences, Faculty of Science, University of Ngaoundere, PO Box 454,
Ngaoundere, Cameroon. Fax: 00 237 22 25 27 71. E-mail: email@example.com
Department of Geology, Faculty of Exact and Applied Sciences, University of N’Djamena, N’Djamena, Chad
The shallow aquifer in the Lake Chad basin is highly vulnerable to pollution. Analysis carried out on 316 wells
and boreholes have showed a tendency towards an increase of nitrate values, exceeding 50 mg l21. Nitrate
concentrations ranged between about 1 and 300 mg l21. Large variation in concentration was observed in wells and
boreholes that are only short distances apart. High concentrations of nitrate in wells, especially in a recharge area
along the sand dunes, or via inﬁltration from river banks, irrigation channels, and inﬁltration of urban wastewater
into groundwater from septic tanks, pose a serious problem for drinking water supply. In Cameroon and Chad, the
results of the investigation indicate a variation of nitrate concentration in groundwater between the two areas. The
primary origin of this pollution is agricultural proliferation activities that are developed and stressed by socio-
economic needs outside the urban area, and by urban expansion within the area served by a decrepit network of
urban area sewers. Substancial differences in values of nitrate concentrations were observed in groundwater from
adjacent wells and boreholes, indicating local rather than regional contamination.
Keywords: Agricultural activities; Cameroon; Chad; Groundwater; Lake Chad basin; Nitrate; Septic tanks
Groundwater is a natural resource with both ecological and economic value which is of vital
importance for sustaining life, health, agriculture and the integrity of ecosystems. Groundwater quality
may be impacted by changes in overlying land use such as industrial development, agricultural activity
and wastewater generation (Barrett, 2004). The contaminants for which epidemiological studies have
suggested a risk associated with their presence in potable water include aluminium, arsenic, disinfection
by-products (DBPs), ﬂuoride, lead, nitrate, radon, pesticides, hydrocarbons and chlorinated
hydrocarbons (Zhang et al., 2004). The most common contaminant identiﬁed in groundwater is
dissolved nitrogen in the form of nitrate ðNO2 Þ. Despite the European Union Directive (CEC, 1991),
q IWA Publishing 2010
2 B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12
the World Health Organization’s guidelines for drinking water quality (WHO, 1984) and the United
States standards for nitrate in drinking water (Chandler, 1989), nitrate levels in groundwater have been
increasing over recent decades in most countries as a result of the drainage of excess fertilizers (Canter,
1997; Razowska-Jaworek & Sadurski, 2005). In Africa and particularly in the Lake Chad basin, scarcity
and water pollution constitute a major challenge for sustainable water resources management, especially
in a semi-arid context. The contamination of the groundwater resource by nitrate ðNO2 Þ is of much
concern in the Lake Chad basin. It is well known that serious and occasionally fatal poisonings in infants
have occurred following ingestion of well waters which contain more than 45 mg l21 NO2 (Srinivasa
Rao, 1998). Nitrate has also been linked with gastric and oesophageal cancer, because of the reaction of
nitrate with amines in the diet-forming carcinogenic nitrosamines (Gilli et al., 1984; Siddiqi et al., 1992).
Elevated nitrogen levels can cause excessive growth of aquatic plants and algae leading to decreases in
dissolved oxygen with its associated implications for aquatic invertebrates in surface waters (Cronin &
Lerner, 2004). Sustainable city development means that these problems must be addressed in order to
minimise the overall threat to groundwater resources (Lerner, 1996). Water quality management mainly
involves the identiﬁcation and analysis of the contaminants, identiﬁcation of their sources and the
possible implementation of remedial measures. Though little studies of nitrate pollution have been done
on a local scale, there is limited groundwater monitoring data to help manage the resource on a regional
scale. Scientists have a duty to address these shortcomings by pointing out the extent of pollution
problems and by advising on the remediation, monitoring and enforcement issues. In this context, the
southern sector of Lake Chad (Cameroon) and the city of N’Djamena (Chad), two populated areas
around Lake Chad, were selected for their growth potential within the aim of a systematic study to
determine the distribution of nitrate contamination in the Quaternary aquifer of the Chad basin and its
sources. Recommendations for further research study are also discussed.
2. Study area descriptions
The southern sector of Cameroon and the adjacent city of N’Djamena, located in the Lake Chad basin,
are the areas considered in this study (Figure 1). The basin is ﬁlled largely with Tertiary and Quaternary
material, which are aquifers. The Quaternary aquifer, because of its high vulnerability to pollution, is the
main focus of this work. It is formed by alluvial deposits which range from between 15 and 70 m thick.
The Quaternary deposits form a shallow unconﬁned water table. In the Chad basin, groundwater forms
an important component of the water supply, providing 90% of drinking water to an estimated 20 million
people. Several shallow wells and boreholes tap groundwater. The depth of the wells varies from less
than 2 m to about 15 m, and the depth of boreholes from 20 to 60 m. Groundwater occurs at depths
varying from 1.0 m to about 40 m below soil level. In Cameroon and Chad, the main uses of groundwater
are domestic and industrial. Untreated wastewater ﬂows along natural channels, where it inﬁltrates or
evaporates. In Cameroon particularly, the study area is characterized by large portions of agricultural
land associated with livestock breeding. Groundwater from wells is employed to supply animals with
drink. Tourism dominates the region’s economy.
The two areas share many similarities in their hydrogeologic and development characteristics. They
have similar semi-arid climates and hydrogeologic settings; they are underlaid by aquifer systems
having substantial storage capacity but limited natural recharge (Djoret, 2000; Ngounou Ngatcha et al.,
2007); they are water deﬁcient in the context of current water demands; they are regional population
B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12 3
Fig. 1. Map showing the two study areas in the Lake Chad basin.
centres; and they support industrial or agricultural economies of national importance. According to
Barber et al. (1996) the concentration of contaminant generally increases with the age of urban
development. There is poor integration of environmental concerns with economic growth, particularly
with regard to groundwater. Thus, there is a risk that the load of contaminants discharged to rivers (the
Chari, Logone and Mayo) and to the Lake will progressively increase with the increasing population
density of the Lake Chad basin.
The principal source of water quality information in this paper is the Ministry of Mines, Water and
Energy’s computerized database in Cameroon. The quality of the original data, especially with regard to
measurement errors, is not fully known. Complementary data for the Chadian parts of the Chad basin
were obtained from Djoret (2000). The chemical composition of water was analyzed for its possible
4 B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12
relation to excess nitrate detection. No analysis has been undertaken for other urban contaminants that
are commonly identiﬁed in other parts of the world, such as petroleum products, chlorinated solvents,
pesticides and heavy metals: it is, therefore, important to undertake monitoring surveys for these
contaminants too. Evaluation of threats to urban groundwater requires the linking of many different
types of data, from the ﬁelds of land use, hydrology, hydrogeology, chemistry, and microbiology
(Cronin & Lerner, 2004). In order to characterize the physical behaviour of samples sites further,
Principal Components Analysis was applied to data from both areas (285 analyses in Cameroon and 31
in Chad). The analyses were carried out with the aid of STATBOX 6.4 statistical software.
4. Results and discussion
Table 1 shows the results (average, minimum and maximum values) of chemical constituents (pH,
EC, nitrate and concentrations of major ions) of groundwater samples (285 in Cameroon and 31 in
Chad). The average groundwater nitrate concentration for the study area is 14.71 mg l21 in Cameroon
and 35.27 mg l21 in Chad. All 100% of the wells or boreholes had detectable nitrate (Table 2), and in
about 3.85% (in Cameroon) and 19.35% (in Chad) of the wells, the water is not suitable for drinking
without treatment, according to EU, US, and WHO standards. The original correlation matrix, given in
Table 3(a) and (b), shows that there is a positive correlation between electrical conductivity and such
cations as calcium, magnesium, and sodium as well as bicarbonate (only in Cameroon), sulphate and
chloride anions. In contrast, there is little positive correlation between electrical conductivity and nitrate
and potassium. In Cameroon (Table 3(a)), there is little positive correlation between nitrate and calcium,
Table 1. Basic statistical parameters of groundwater chemical composition in the selected areas.
Ion Area No. samples Min. Max. Average Standard deviation
pH Cameroon 285 6.0 8.7 7.64 0.51
Chad 31 7.8 7.8 7.08 0.36
EC (mS cm21) Cameroon 285 100.0 2,400.0 463.53 281.73
Chad 31 58.0 3,660.0 711.84 834.69
Ca (mg L21) Cameroon 285 6.0 681 87.56 80.68
Chad 31 4.21 420.8 63.82 81.90
Mg (mg L21) Cameroon 285 1.00 50.0 10.03 7.04
Chad 31 1.38 143.5 17.38 28.28
Na (mg L21) Cameroon 285 2.00 506.0 47.24 53.41
Chad 31 2.60 321.8 52.24 71.93
K (mg L21) Cameroon 285 0.10 102.0 4.88 8.09
Chad 31 2.49 68.98 11.90 12.87
HCO3 (mg L21) Cameroon 285 52.00 714.00 261.44 117.46
Chad 31 26.84 459.94 193.78 104.72
SO4 (mg L21) Cameroon 285 0.10 450.00 29.69 61.24
Chad 31 0.15 1,890.00 150.55 396.78
Cl (mg L21) Cameroon 285 1.00 99.50 12.07 14.20
Chad 31 0.33 316.60 35.58 66.94
NO3 (mg L21) Cameroon 285 1.00 300.00 14.71 31.55
Chad 31 8.80 167.20 35.27 34.34
B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12 5
Table 2. Nitrate concentration in groundwater in the selected areas.
Percentage of samples with NO3
Number of samples with NO3 concentration of: concentration of:
Area No. samples 0 – 15 mg L21 16 –50 mg L21 .50 mg L21 0 – 15% 16 – 50% .50%
Cameroon 285 227 47 11 79.65 16.50 3.85
Chad 31 4 21 6 12.90 67.75 19.35
magnesium, and chloride, while in Chad (Table 3(b)), nitrate only correlates with potassium.
The Eigenvalues and the percentages of accumulation or weight of the original variables (Table 4) show
that, from the 10 principal components calculated, the ﬁrst ﬁve in Cameroon and the ﬁrst three in Chad
explain about 81.20% of the total variance. The correlation between variables and principal components
are given in Table 5. In Figure 2(a) and (b), the variables are represented according to axes I and II which
account for the greater part of the variance, and it is evident that axis I groups almost all of the variables
except NO2 . In the two areas, axis II is characterized by NO2 . Moreover, in Chad, axis II is correlated
positively to potassium. The Factorial plane I– II reﬂects the most important information, with factor
I (38.26% of the variance in Cameroon and 53.81% of the variance in Chad) and factor II (13.88% of the
variance in Cameroon and 15.27% of the variance in Chad) characterized by nitrates. In the two areas,
the contribution of factors I and II to the total variance is not similar. The spatial distribution of the
Table 3. Matrix of correlation between the 10 variables in (a) the Cameroon area and (b) the Chad area.
EC pH Ca Mg K Na HCO3 Cl SO4
(a) Cameroon area
2 pH 0.00
3 Ca 0.41 2 0.23
4 Mg 0.53 0.11 0.41
5 K 0.16 20.09 0.03 0.11
6 Na 0.54 20.08 0.07 0.29 0.20
7 HCO3 0.61 0.06 0.49 0.57 0.21 0.56
8 Cl 0.55 20.03 0.31 0.41 0.07 0.38 0.29
9 SO4 0.55 2 0.13 0.37 0.50 0.19 0.62 0.39 0.48
10 NO3 0.33 20.07 0.28 0.25 20.04 20.08 0.04 0.35 0.03
(b) Chad area
2 pH 2 0.29
3 Ca 0.93 20.31
4 Mg 0.95 20.29 0.97
5 K 0.45 20.10 0.37 0.38
6 Na 0.64 20.14 0.36 0.40 0.23
7 HCO3 0.30 20.13 0.28 0.19 0.04 0.42
8 Cl 0.89 20.31 0.87 0.90 0.43 0.40 0.05
9 SO4 0.95 20.27 0.94 0.98 0.39 0.45 0.10 0.90
10 NO3 0.16 0.02 0.09 0.04 0.65 0.22 2 0.07 0.16 0.06
Notes: (1) electrical conductivity; (2) pH; (3) calcium; (4) magnesium; (5) potassium; (6) sodium; (7) bicarbonate; (8) chloride;
(9) sulphate; (10) nitrate.
6 B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12
Table 4. Eigenvalues of table of matrix correlation in the selected areas.
Eigenvalue Total variance (%) Total variance (cumulative %)
Number of variable Cameroon Chad Cameroon Chad Cameroon Chad
1 3.83 5.38 38.26 53.81 38.26 53.81
2 1.39 1.53 13.88 15.27 52.14 69.09
3 1.15 1.21 11.52 12.14 63.66 81.22
4 0.91 0.88 9.12 8.82 72.78 90.05
5 0.87 0.57 8.74 5.66 81.52 95.71
6 0.58 0.28 5.83 2.76 87.35 98.47
7 0.47 0.12 4.66 1.20 92.01 99.68
8 0.39 0.02 3.92 0.21 95.94 99.88
9 0.29 0.01 2.85 0.08 98.79 99.96
10 0.12 0.00 1.21 0.04 100.00 100.00
variables and the individuals, according to the two ﬁrst components, is presented in Figure 3(a) and (b).
The result of the Principal Components Analysis suggests that although the two areas are part of the Lake
Chad basin, there are differences in their water chemistry that are not very apparent. The major
differences in the composition of groundwater from the two sampling areas are the concentrations of
nitrate, sulphate, chloride and potassium. It can be concluded that factor I represents the natural
processes by which water acquires its chemical characteristics, whereas factor II represents the
Table 5. Correlation between principle component and variables.
Variable Area CP1 CP2 CP3 CP4 CP5 CP6 CP7 CP8 CP9 CP10
EC Cameroon 0.43 0.04 0.08 20.10 0.06 2 0.31 20.05 20.24 0.79 2 0.08
Chad 0.43 2 0.04 0.05 0.10 0.09 0.02 20.09 0.00 2 0.13 0.88
pH Cameroon 20.04 2 0.11 0.87 0.03 0.19 0.12 20.26 20.31 2 0.14 2 0.07
Chad 20.15 0.17 2 0.02 0.96 2 0.12 2 0.01 0.05 0.02 2 0.01 2 0.01
Ca Cameroon 0.30 0.36 2 0.21 0.51 2 0.21 0.16 20.42 20.26 2 0.16 2 0.37
Chad 0.41 2 0.12 2 0.10 0.04 2 0.26 2 0.26 20.20 0.70 2 0.29 2 0.24
Mg Cameroon 0.37 0.10 0.27 0.24 0.03 0.36 0.60 0.39 0.06 2 0.27
Chad 0.41 2 0.12 2 0.15 0.09 2 0.10 2 0.05 20.21 20.08 0.84 2 0.09
K Cameroon 0.13 2 0.35 2 0.29 0.22 0.84 0.13 20.10 20.02 2 0.02 2 0.05
Chad 0.22 0.59 0.02 20.10 2 0.32 0.69 20.03 0.08 2 0.01 2 0.05
Na Cameroon 0.34 2 0.45 2 0.05 20.31 2 0.15 2 0.36 0.09 20.06 2 0.39 2 0.51
Chad 0.24 0.04 0.56 0.13 0.70 0.18 20.03 0.19 0.05 2 0.24
HCO3 Cameroon 0.39 2 0.16 0.14 0.44 2 0.10 2 0.42 20.08 0.25 2 0.19 0.56
Chad 0.11 2 0.22 0.75 0.00 2 0.55 2 0.10 0.15 20.21 2 0.01 2 0.04
Cl Cameroon 0.35 0.19 0.03 20.49 0.08 0.24 20.51 0.51 2 0.05 0.06
Chad 0.40 2 0.01 2 0.21 0.02 0.07 2 0.05 0.88 20.06 2 0.03 2 0.10
SO4 Cameroon 0.39 2 0.19 2 0.14 20.21 2 0.18 0.50 0.16 20.49 2 0.10 0.43
Chad 0.41 2 0.09 2 0.18 0.11 0.06 0.02 20.33 20.63 2 0.42 2 0.30
NO3 Cameroon 0.16 0.65 0.00 20.21 0.38 2 0.31 0.27 20.24 2 0.35 0.11
Chad 0.09 0.73 0.12 20.11 0.05 2 0.64 20.05 20.12 0.04 0.01
B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12 7
Fig. 2. Correlation circles: Axes I and II, taking into account only the variables: (a) in the Cameroon area, and (b) in the
prevalence of pollution (Esteller & Andreu, 2005). According to Kross et al. (1993), the depth of the well
is an important determinant of nitrate concentration in Iowa (USA). Testing in the Lake Chad basin, no
correlation was observed between a well’s depth and nitrate concentrations (Figure 4(a) and (b)). In the
two areas, most depths to water are 5 – 20 m; a few wells are as deep as 30 m. High concentration of
nitrate occur at depths of , 20 m. Values that were higher than 50 mg l21 corresponded to sites which
have good contact with the recharge area, while the lowest values are associated with areas that are
underlain principally by clayey deposits. According to Sapek (2005), the most frequent nitrate content in
cropped soils ranged between 30 and 200 kg ha21 NO2 N in a 100 cm layer of topsoil. In experimental
work, Gerritse et al. (1990) have indicated that if 80 kg/ha of nitrogen applied to sewered urban areas
reached the water table, mean nitrate concentration should be about 40 mg l21 as N. Nitrate
concentrations in groundwater in the selected areas are relatively high compared with nitrate
concentrations that occur in rural areas with intensive agriculture where domestic and mineral fertilizers
are used (Sapek, 2005) or in urban areas due to the collection of domestic wastewater in septic tanks
(Fikret & Gultekin, 1997). Concentration of nitrates in groundwater is greater in urban areas than in
agricultural regions. Despite such evidence of widespread sources of inorganic pollution, the identity of
the sources remains partially unresolved.
In the areas selected, nitrate accumulation in groundwater has three major sources: (1) agricultural
activities; (2) recharge of groundwater through inﬁltration from rivers banks and irrigation channels; and
(3) inﬁltration of wastewater into groundwater from septic tanks. More than 85% of the population in the
two selected areas lives in unsewered accommodation and so there is likely to be a signiﬁcant amount of
domestic wastewater disposed to ground, particularly in shantytowns which are highly populated areas.
When septic tanks exist, every apartment building and house collects its own wastewater in separate septic
tanks. The distance between two adjacent septic along the same street is about 10– 20 m. Septic tanks
contribute large volumes of wastewater to the subsurface environment and are the most frequently
reported cause of groundwater contamination in urban areas. With the greatly accelerated urbanization of
the last decades, total sewage discharges from domestic and industrial sources is discharged via open
drains to rivers (the Mayo and Logone in Cameroon, and the Chari in Chad) and/or to agricultural lands
with no treatment. According to Graniel et al. (1999), elevated ratios of nitrate to chloride concentrations
8 B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12
(a) Variables and individuals (axis F1 and F2 : 52 %)
Axis F2 (14 %)
cub113 cub1 0
cub75 1 Cl
0.2 cub10 cub235 cub136
cub163 cub261 Mg
cub49 cub162 cub166 Cond
cub1 cub60 cub133 cub201
cub1 HCO 3
cub1 cub4 cub172 cub178
cub168 cub147 cub39
–0.4 cub1 cub34K cub139
57 cub174 cub152
–0.5 0 0.5 1 1.5
Axis F1 (38 %)
(b) Variables and Individuals (axis F1 and F2 : 69 %)
Axis F2 (15 %)
1 PD 24
0.5 PD 7
pH PD 8 PD20
0 PD 56
FD PD 1
PD 21 Cl 1
2 0 FD4
FD 8 5 12 PD 5 SO4
PD 1 HC
PD 9 FA D1 O3
FD 12 1
–0.5 FD3 FD 11
–1 –0.5 0 0.5 1 1.5 2 2.5
Axis F1 (54 %)
Fig. 3. Plot of principal components: Axes I and II, taking into account variables and individuals (a) in the Cameroon area, and
(b) in the Chad area.
(.2:1) are indicative of domestic sewage loading to groundwater. Continued urbanisation is, therefore,
expected to increase concentrations of inorganic contaminants in groundwater. Concentrations of
contaminants are likely to be diluted by the large volume of river ﬂow, but there is a risk that some
contaminants will accumulate in the aquifer with ongoing river recharge (Alderwish et al., 2004).
Oguntola (2004) reported the occurrence of various waterborne diseases including diarrhea (in the most
vulnerable groups: children below 5 years and the elderly), typhoid fever, Hepatitis A, cholera,
gastroenteritis and dysentery, as a result of drinking contaminated groundwater in the Chad basin.
According to Zhang et al. (2004), the microbial contaminants of greatest concern in drinking water are
B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12 9
Fig. 4. Relationships between nitrate concentration and groundwater static level: (a) in the Cameroon area, and (b) in the
usually of faecal origin. Urban groundwater problems evolve over many years or decades, partly reﬂecting
the growth of urban populations and increased water demand and waste generation. The consequence of
urban expansion and population growth is that water tables are lowered and contamination of shallow
groundwater occurs through disposal of residential and industrial waste to the ground.
Adequate nitrogen (N) is essential for good crop production; however, excessive use of nitrogen-
enriched fertilizers can cause environmental damage, namely contamination of groundwater. In the Lake
Chad basin, irrigated agriculture is an important economic activity in the ﬂood plain where the top
clayey formation (stratum or layer that prevents or restricts the saturated movement of water in the soil)
is absent and where a large amount of groundwater recharge takes places. Manure and mineral fertilizers
are used extensively in agriculture (it was not possible for us to obtain the quantity of nitrogen fertilizer
applied per hectare of land).
Additionally, groundwater is in common use for livestock breeding in the Cameroon area, except
where surface water supply is available. Nitrogen from anthropogenic sources (pastoral agriculture,
fertilizers and waste disposal) undergoes mineralization-immobilization, ﬁxation, nitriﬁcation (from
nitrogen excreted by humans) and denitriﬁcation (nitrogen inputs into groundwater are retained in the
aquifer systems) (Chen et al., 2005).
The best way to mitigate the groundwater pollution by nitrate from agricultural sources is through the
implementation of Best Agricultural Management Practices and the effective education of farmers and
rural area populations. The strategy is to increase the nitrogen efﬁciency in agricultural production as a
way to reduce nitrate losses. This covers the entire agricultural production—cropping systems as well as
livestock husbandry (Sapek, 2005). As surface water is the main source of groundwater recharge,
essential elements of surface water protection include strict regulation of human activity, and
modernisation of various systems of sewage accumulation and treatment.
10 B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12
A comprehensive groundwater monitoring programme is needed, which includes delineation of
responsibilities for data collection, sample and data analyses, and reporting. This programme should
assign centralised responsibility for the monitoring database. Groundwater monitoring plays an
important role in determining the continuing viability and effectiveness of wastewater reuse
programmes, a technique which could be an integral component of water conservation in any country in
the long term in selected areas.
As the Lake Chad basin is shared, additional problems in water resource management include:
. identiﬁcation of problems speciﬁc to particulars industries. Industrial inputs into sewage systems must
be strictly controlled. Initiating management programmes for reducing or preventing the generation of
waste during production processes or other operations would be a ﬁrst step to an economically and
environmentally sound way of dealing with hazardous wastes;
. installation of wastewater treatment plants for processing industrial efﬂuent. Reuse of domestic
wastewater could be an important strategy for conserving water resources in areas suffering from
major water shortages.
5. Conclusions and future strategies
The goal of this study was to evaluate the regional distribution of nitrate in groundwater and to
identify their probable sources. Although the two selected areas are located in the same basin, the nitrate
concentrations in Chad are commonly much higher than in Cameroon. No good linear correlation exists
between nitrate and other major ions. The main source of contamination is variable across both the areas.
The magnitude of the pollution depends on human activities, including agriculture, livestock breeding,
industry and urbanization. Regarding the distribution of high nitrate concentration in the selected areas,
septic tanks contribute large volumes of wastewater to the subsurface environment and are the most
frequently reported cause of groundwater contamination associated with the outbreak of diseases. The
high prevalence rates of waterborne and water-related diseases are a direct manifestation of these poor
sanitation and hygiene standards.
The risk of nitrate contamination in the two selected areas is already signiﬁcant. For this reason,
remedial action programmes are needed, focusing on community health education and on improving water
supply, sewerage systems and waste disposals at all levels of the community. The protection of
groundwater resources should be identiﬁed as a key management issue in the Lake Chad basin. Thus,
a regional groundwater quality monitoring network should be developed to characterise water quality
within the Lake Chad basin. It is important to carry out detailed soil studies and to suggest alternatives
aimed at detecting and reducing such risks. Rational and ecologically optimal planning of modern city
growth should include evaluations of economics and environmental protection, such as the treatment of
wastewater in order to reduce the potential contamination of groundwater. Otherwise, the best way to
mitigate the pollution of groundwater by nitrate from agricultural sources is through the implementation of
best agricultural management practices and the effective education of farmers and rural area populations
in order to prevent the release of potential contaminants in the vicinity of groundwater-fed water points.
Moreover, better chemical handling practices must be adopted by industry. There is clearly a need for
further research, using stable isotope ratios of nitrogen (15N/14N) and microbiological indicators, to
B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12 11
establish the sewage contamination of groundwater in the Lake Chad basin, and to ﬁnd evidence of
multi-point source sewage contamination of shallow groundwater. Better co-operation between
municipal authorities, government bodies and other decision-making bodies is essential to look at the
ﬁnancial resource available for groundwater protection. In fact, at present, scientists’ problems are
linked to a lack of resources for funding pollution control measures.
Alderwish, A., Hefny, K. & Appleyard, S. (2004). Rapidly-urbanising arid-zone cities. In Urban Groundwater Pollution.
Lerner, D. N. (ed.). AA Balkema Publishers, The Netherlands, pp. 134– 153.
Barber, C., Otto, C. J., Bates, L. E. & Taylor, K. J. (1996). Evaluation between land-use changes and groundwater quality in a
water supply catchment, using GIS technology: the Gwelup wellﬁeld. Hydrogeology Journal, 4(1), 20 – 29.
Barrett, M. H. (2004). Characteristics of urban groundwater. In Urban Groundwater Pollution. Lerner, D. N. (ed.). AA Balkema
Publishers, The Netherlands, pp. 29 – 51.
Canter, L. W. (1997). Nitrates in Groundwater. Lewis publishers, New York, USA.
CEC (Commission of the European Communities) (1991). EU Council Directive 91/676/EEC Concerning the Protection of
Waters Against Pollution Caused by Nitrates from Agricultural Sources. Commission of the European Communities,
Chandler, J. (1989). Nitrates in water. Water Well Journal, 43(5), 45 – 47.
Chen, J., Tang, C., Sakura, Y., Yu, J. & Fukushima, Y. (2005). Nitrate pollution from agriculture in different hydrogeological
zones of the region groundwater ﬂow system in the North China Plain. Hydrogeology Journal, 13(3), 481–492.
Cronin, A. A. & Lerner, D. N. (2004). Mature industrial cities. In Urban Groundwater Pollution. Lerner, D. N. (ed.).
AA Balkema Publishers, The Netherlands, pp. 109–131.
Djoret, D. (2000). Etude de la recharge de la nappe du Chari Barguimi (Tchad) par les methodes chimiques et isotopiques.
These Doctorat, Universite d’Avignon et des pays de Vaucluse.
Esteller, M. V. & Andreu, J. M. (2005). Anthropic effects on hydrochemical characteristics of the Valle de Toluca aquifer
(Central Mexico). Hydrogeology Journal, 13(2), 378– 390.
Fikret, K. & Gultekin, G. (1997). Impacts of human activities on groundwater quality of an alluvial aquifer: a case study of the
Eskisehir plain, Turkey. Hydrogeology Journal, 5(3), 60 – 70.
Gerritse, R. G., Barber, C. & Adeney, J. A. (1990). The impact of residential urban areas on groundwater quality: Swan Coastal
Plain, Western Australia: Australia CSIRO Water Resource Series Report (3). CSIRO, Division of Water resources,
Gilli, G., Corrao, G. & Favilli, S. (1984). Concentrations of nitrates in drinking water and incidence of gastric carcinomas: ﬁrst
descriptive study of the Piemonte Region, Italy. The Science of the Total Environment, 34(1 – 2), 35 – 48.
Graniel, E., Morris, L. B. & Carrillo-Rivera, J. J. (1999). Effects of urbanisation on groundwater resources of Merida, Yucatan,
Mexico. Environmental Geology, 37(4), 303– 312.
Kross, B. C., Hallberg, G. R., Bruner, D. R., Sherry Holmes, K. & Johnson, J.K. (1993). The nitrate contamination of private
well water in Iowa. American Journal of Public Health, 83(2), 270– 272.
Lerner, D. (1996). Urban groundwater: an asset for the sustainable city. European Water Pollution Control, 6(5), 43 –51.
Lerner, D. N. & Barrett, M. H. (1996). Urban groundwater issues in the United Kingdom. Hydrogeology Journal, 4(1), 80 – 89.
Ngounou Ngatcha, B., Mudry, J. & Sarrot Reynauld, J. (2007). Groundwater recharge from rainfall in the southern border of
Lake Chad in Cameroon. World Applied Sciences Journal, 2(2), 125– 131.
Oguntola, J. A. (2004). Management of transboundery aquifer systems in Africa: a case study of the Lake Chad Basin
Commission. In Managing Shared Aquifer Resources in Africa. IHP-VI Series on Groundwater 3. Appelgren, B. (ed.).
UNESCO press, Paris, pp. 203– 208.
Razowska-Jaworek, L. & Sadurski, A. (2005). Nitrates in Groundwater: Selected Papers from the European Meeting of the
International Association of Hydrogeologists, Wisla, Poland, 4 – 7 June 2002. AA Balkema Publishers, The Netherlands.
Sapek, A. (2005). Agricultural activities as a source of nitrates in groundwater. In Nitrates in Groundwater: Selected Papers
from the European Meeting of the International Association of Hydrogeologists, Wisla, Poland, 4 – 7 June 2002. AA Balkema
Publishers, The Netherlands, pp. 3 – 13.
12 B. N. Ngatcha and D. Daira / Water Policy Uncorrected Proof (2010) 1–12
Siddiqi, M., Kumar, R., Fazali, Z., Spiegelhalder, B. & Preussmann, R. (1992). Increased exposure to dietary amines and nitrate
in a population at high risk of oesophageal and gastric cancer in Kashmir (India). Carcinogenesis, 13(8), 1331 –1333.
Srinivasa Rao, N. (1998). Impact of clayey soils on nitrate pollution in the groundwater of the Lower Vamsadhara River basin,
India. Hydrological Sciences Journal, 43(5), 701– 714.
WHO (World Health Organization) (1984). Guidelines for Drinking Water Quality, Vol. 3: Drinking Water Quality Control in
Small Community Supplies. WHO, Geneva, Switzerland.
Zhang, S,, Howard, K,, Otto, C., Ritchie, V., Sililo, T. N. O. & Appleyard, S. (2004). Sources, types, characteristics and
investigation of urban groundwater pollutants. In Urban Groundwater Pollution. Lerner, D. N. (ed.). AA Balkema
Publishers, The Netherlands, pp. 53 – 107.
Received 16 February 2009; accepted in revised form 3 March 2009. Available online 4 January 2010