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Urban groundwater management and protection in Sub-Saharan Africa

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Groundwater is the preferred source for piped water supplies in many urban areas across sub-Saharan Africa and its development is forecast to increase dramatically in an attempt to improve urban water supply coverage. The provision of clean drinking water while providing adequate sanitation and storm-water disposal has become a major challenge for many cities. The hydrogeology and groundwater situation of Addis Ababa, Abidjan, Cape Town, Dakar, Lagos, and Lusaka are highlighted as examples that illustrate the status of urban groundwater in sub-Saharan Africa. The history of urban development and the current groundwater management practices under each case example is also discussed. The main man-made impacts on groundwater in the various cities under consideration are rapid urbanisation and changes in land use surrounding cities. The impact of urbanisation is not only viewed in terms of groundwater quality but as it affects recharge.
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CHAPTER 14
Urban groundwater management and protection in
sub-Saharan Africa
S.M.A. Adelana
Geology Department, University of Ilorin, Ilorin, Nigeria
A. Tamiru
Department of Earth Sciences, AddisAbaba University, Addis Ababa, Ethiopia
D.C.W. Nkhuwa
The University of Zambia, School of Mines, Geology Department, Lusaka, Zambia
C. Tindimugaya
Ministry of Water and Environment,Water Resources Management Department, Entebbe, Uganda
M.S. Oga
Université de Cocody, UFR des Sciences de la Terre et des Ressources Minières,
Abidjan, Côte d’Ivoire
ABSTRACT: Groundwater is the preferred source for piped water supplies in many urban
areas across sub-Saharan Africa and its development is forecast to increase dramatically in
an attempt to improve urban water supply coverage.The provision of clean drinking water
while providing adequate sanitation and storm-water disposal has become a major challenge
for many cities. The hydrogeology and groundwater situation of Addis Ababa, Abidjan,
Cape Town, Dakar, Lagos, and Lusaka are highlighted as examples that illustrate the status
of urban groundwater in sub-Saharan Africa. The history of urban development and the
current groundwater management practices under each case example is also discussed. The
main man-made impacts on groundwater in the various cities under consideration are rapid
urbanisation and changes in land use surrounding cities. The impact of urbanisation is not
only viewed in terms of groundwater quality but as it affects recharge.
1 INTRODUCTION
In urban areas across sub-Saharan Africa (SSA), the density of population and industry
often results in serious problems of groundwater quantity and quality. The United Nations
Population Division (UNPD, 2005) predict that global urban population will increase from
3 billion in 2000 to nearly 8 billion in 2030. Nearly all of this increase is expected to take
place in developing countries as urban population will grow at an annual average rate of
1.9% compared to global population growth rate of 1%. The rapid rate of urbanisation
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232 Applied groundwater studies inAfrica
in Africa has far exceeded the management and financial capabilities of all the levels of
governments since the 1960s. This is a crucial fact that poses challenge to water resources
management in SSA.
African cities have a long history of water supply both from surface water and ground-
water. However, due deteriorating quality and quantity of surface water through increased
urbanisation and industrialisation, and the high costs of developing new dams, urban
groundwater is being seen as an increasingly valuable resource. However, recent inves-
tigations reveal that key groundwater resources are either polluted or at risk of pollution.
The occurrence and use of groundwater within the general area of any city depends
not only on geology, climate, and the availability of other sources of water, but also on
the history of development. Investigations in African capital cities show similar problems
across the continent, but with some key differences due to the diverse political, cultural and
economic conditions across SSA.Yet a unifying theme for all is the need for freshwater and
its sustainability. The provision of clean drinking water, adequate sanitation and stormwater
disposal has become a major challenge for most African cities.
Groundwater resources are used to supply many urban centres across sub-SaharanAfrica.
The large cities that are groundwater-dependent are shown in Figure 1 (Morris et al., 2003).
Recent development and increased groundwater demand would have added more cities to
this list in the last few years. In cities where groundwater is a small fraction of total water
use, it still represents a stable source of water, when surface water resources may fluctuate.
This paper reviews the current status of urban groundwater in sub-Saharan Africa by
means of some selected case histories. The objective is to describe the importance of ground-
water in water supply to major cities in SSA and examine the impact of urbanisation on qual-
ity and quantity of groundwater. The history of urban development, current groundwater
management practises, policy implications and future challenges are also discussed.
2 INTRODUCTION TO THE CASE STUDIES
2.1 Addis Ababa
The city of AddisAbaba has a population of 4 million of which 50% have no direct access
to the Municipal water supply system (derived from both surface water and groundwater).
The city was established as a capital of Ethiopia in 1886 and has since grown to become the
largest urban and commercial centre in the country. It is located in the central part of
the country at the edge of the western escarpment of the Ethiopian Rift (Figure 1). In
the 1970’s the size of the city was 37km2, while a satellite image in 1999 revealed that the
size increased 230 km2(Figure 2). Within 29 years the city expanded at an average rate of
6.7 km2/a. According to projection of the United Nations, Addis Ababa will become the
fourth largest city in Africa by 2015 (UNPD, 2005).
For the first 58 years (1886–1944), the water supply for the city was derived from
groundwater in the form of springs located at the foot of the Entoto ridge (northern part
of the city) and also from dug wells located in the central and southern lower part of
the city (Alemayehu, 2006). Additional demand necessitated treatment of surface water
derived from three surface dams (Gefersa, Legedadi and Dire). However, the exponential
population growth in the city demanded further water resources, and the Akaki well field
in the southern parts of the city was developed to supplement the growing water demand.
Individual boreholes at the Akaki well field can yield as much as 80l/s.
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Urban groundwater management and protection 233
Figure 1. Examples of cities heavily dependent on groundwater in Africa (adapted from Morris
et al., 2003).
The current demand has created a supply shortfall of about 50%. Large numbers of private
boreholes abstract water from the volcanic aquifer with yields as much as 15l/s. The large
number of private boreholes has caused well interference and a lowering of water-table.
The water quality from private boreholes within the city can also be poor.
Geologically, the city is dominated by volcanic materials of different ages and composi-
tions (Alemayehu et al., 2005). The Miocene-Pleistocene volcanic succession in the Addis
Ababa area from bottom to top are: Alaji basalts and rhyolites, Entoto silicics, Addis Ababa
basalts, Nazareth group, and Bofa basalts. The Alaji group volcanic rocks (rhyolites and
basalts) show variation in texture from highly porphyritic to aphyric basalts and there is an
intercalation of gray and glassy welded tuff.
The main aquifers in AddisAbaba are:
1. Shallow aquifer: composed of slightly weathered volcanic rocks and alluvial sediments.
Depth to groundwater in this aquifer reaches up to 50 m.
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234 Applied groundwater studies inAfrica
Figure 2. Borehole location in Addis Ababa (after Alemayehu et al., 2005).
2. Deep aquifers: composed of fractured volcanic rocks that contain relatively fresh ground-
water. These aquifers are mainly located in the southern part of the project area of the
city. The depth in some places reaches as high as 180m.
3. Thermal aquifer: that is situated at depth greater than 300 m and located in the centre of
the city. The existence of these aquifers is manifested by deep circulating thermal water
with few hot wells drilled along the major Filwoha fault.
More than 500 boreholes have been inventoried in the city (Figure 2) that provides water
for domestic and industrial uses. These boreholes are currently tapping water from the
volcanic rock reservoir at variable rate.The water abstracted from volcanic aquifers by the
municipality is around 40,000 m3/d (out of which 30,000 m3/d is from Akaki well field).
Other private and governmental institutions extract as much as 50,000 m3/d with overall
total abstraction of 90,000 m3/d. Both in central and eastern part of the city, groundwater
occurs within the confined aquifer. Therefore, the main groundwater potential areas are the
eastern and southern part of the city (Alemayehu, 2006).
2.2 Abidjan
Abidjan is the most populous city of Cote D’Ivoire (formerly Ivory Coast) with 4 million
people, more than a fourth of the total country’s population estimated at 15 millions (INS,
2001) It is an industrial city situated along the Atlantic Ocean coastline (Figure 1). The
great region of Abidjan constitutes the central part of a coastal sedimentary basin which
covers a surface of 16,000km2between the latitudes of 500 and 530 N and the longitudes
of 300 and 600 W (Figure 3). The climate of the area is sub-equatorial, characterized by
two rainy seasons (March–July and September–November) separated by two relatively dry
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Urban groundwater management and protection 235
Figure 3. Geology ofAbidjan and location of main boreholes.
periods. The annual mean rainfall is between 1500 and 2000 mm for an average temperature
of 27C (monthly temperature range 24–30C). The vegetation is a clear forest near the
coastline and becomes dense further inland.
Like other coastal cities of WesternAfrica, the recent increase of population has resulted
in environmental problems such as the deterioration of drinking water quality and quantity
(Kouadio et al., 1998; Jourda, 2003, 2004; Soro, 2003). Although there are rivers in
this area, the water supply of the Abidjan area is mainly from two shallow unconfined
sedimentary aquifers: the Continental Terminal aquifer (CT), the most important aquifer;
and the Quaternary aquifer along the coast.
The Quaternary deposits are marine sands (Nouakchottien) and fine sands (Oogolien).
This aquifer is highly vulnerable to pollution because its piezometric surface is very close
to the ground surface. In the Continental Terminal aquifer, both fluviatile (CT3) and clayey
sands (CT4) are hydrologically important. The aquifer (CT3) may be confined when the
upper parts of CT3 are clay rich; where there is no clay between CT3 and CT4 deposits,
the CT3 and the CT4 are interconnected.
The hydraulic conductivity of the CT aquifer is variable due to lateral changes in the grain
size of water-bearing sediments (100m/d in the sands and the sandstones and 0.1 m/d in the
clayey sands).The transmissivity values can be as high as 10,000 m2/d while porosity values
range from 0.05 to 0.20. The regional groundwater flow occurs from north to south, i.e.
towards the lagoon. The hydraulic conductivity of the Quaternary aquifer ranges between
3.5 and 100 m/d. The hydraulic gradient increases up to 3‰ close to the lagoon. The flow
rates are low compare to that of the CT aquifer: 0.6 to 6l/s for the Quaternary aquifer and
2 to 90 l/s for the CT aquifer (Oga et al., this volume).
Deeper in thebasin, around 200 m belowthe groundsurface, the Maestrichtiancarbonates
and sandstones constitute a confined aquifer. This aquifer is artesian with a potentiometric
surface at +27 m above the sea level. Only one borehole of depth 190m (from the SADEM
Company) draws its water from this aquifer.
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2.3 Cape Town
The City of Cape Town is a large urban area with a high population density, an intense move-
ment of people, goods and services, extensive development and multiple business districts
and industrial areas. It represents centres of economic activity with complex and diverse
economies, a single area with integrated development planning and strong interdependent
social and economic linkages. The City of Cape Town includes the Cape Metropolitan
Council, Blaauwberg, Cape Town CBD, Helderberg, Oostenberg, South Peninsula and
Tygerberg (Figure 4); and falls within the semi-arid region of the Western Cape.
Cape Town in its eastern edge and its suburbs is underlain by Cenozoic sands (Cape Flats)
up to the foothills of the first mountain chains to the east. The mountains are underlain
by the oldest rocks in the area (830 to 980 Ma), namely the Malmesbury Group, which
consists of phyllitic shale and siltstone, quartz schist, quartzitic greywacke and sandstone
(Theron et al., 1992). To the south, the mountains of the Cape Peninsula with the Cape
Granite intrusions and the mountain ranges east of False Bay and farther northwards form
the higher terrains. The thickness of the Table Mountain Group varies from 1200 to 2100 m
in the area, and it is sub-divided into eight Formations.
The Cape Flats is within the sphere of the major catchments within greater Cape Town
area, where runoff is mostly generated in the mountain ranges in the southeast and theTable
Mountain and Cape Peninsula Mountains in the southwest. The Berg, Diep, Mosselbank
and Eerste Rivers constitute the most important drainage systems. Sandy lowlands with
minimal runoff and a high water-table extend over the central area.The greater Cape Town
Metropolitan Area lies on one of the most extensive sand aquifers in South Africa, and the
supply potential of groundwater from this aquifer is highly significant. This extensive sand
aquifer, called the Sandveld Group, is hydrogeologically divided into four main units: the
Cape Flats unit, the Silwerstroom-Witzand unit in the Atlantis area, the Grootwater unit in
theYzerfontein region and the Berg River unit in the Saldanha area.Yield analysis of about
497 boreholes in the Sandveld Group indicates that 41% of boreholes yield 0.5 l/s and less
while 30% yields 2 l/s and more (Meyer, 2001).
2.4 Dakar
Dakar is the capital city of Senegal (Figure 1), and one of the cities in SSA that relies
heavily on groundwater for potable supply, both from shallow private hand-dug-wells and
from deeper public water boreholes. The city has witnessed high population growth (2
million people) during the last three decades (Cissé et al., 2000). It is not only a fast growing
urban centre but the high density of population (much of which are in unplanned substandard
housing with no services) has resulted in serious degradation groundwater quality. In Dakar
and its suburbs, on-site sanitation, lack of organized domestic waste disposal and pollution
from industries pose serious threat to water supply (Cissé et al., 2004).
There are two aquifer systems in the area around Dakar (Figure 5): a semi-confined
basaltic aquifer in the western part and the unconfined Thiaroye aquifer in the eastern
part (Tandia et al., 1998). Sediments of the Thiaroye aquifer belong to the Senegalese
superficial aquifer, which consists largely of fine- and medium-grained sands with porosity
of 20% and hydraulic conductivity between 10 and 5000 m2/d (Cisse et al., 2000). With
population growth, water demand has drastically increased, inducing saltwater intrusion in
many dugwells and piezometers in the local coastal aquifers (Tandia et al., 1998).
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Urban groundwater management and protection 237
Figure 4. The city of Cape Town Metropolitan Municipality with population density.
2.5 Lagos
Lagos is located within the Western Nigeria Atlantic coastal zone consisting largely of
coastal creeks and lagoons developed by barrier beaches and situated on stratified series of
sedimentary rocks made up of silt, clay, peat or coal associated with sand deposition. Lagos
is located on latitude 63450 North, and 31959 East of the Greenwich Meridian (see
Figure 1).
Lagos, which was until 1991 the federal capital city of Nigeria, continued to witness
a high increase in population growth and presently has the highest population density in
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238 Applied groundwater studies inAfrica
Figure 5. Location of Dakar city in the western part of Senegal showing Thiaroye and basaltic
aquifers.
Nigeria. It is one of the largest cities in Africa (second only to Cairo in Egypt) and remains
the commercial capital of Nigeria even after the seat of government was moved to Abuja.
The rate of population growth is about 300,000 persons per annum with an average density
of 20,000 persons/km2. With a total land area of about 3600km2and current annual growth
rate of 4%, Lagos is expected to be one of the world’s five megacities in 2015. This
demographic expansion had great consequence on municipal water supply system and
increased the problem of waste management within the city. The area is generally low-
lying with several points virtually close to sea-level. Lagos is built on the mainland and the
series of islands surrounding Lagos Lagoon (Figure 6).
In the city of Lagos, there is pressure on groundwater resources; more problems arise
because of the potentially contaminating human activities developed above the aquifers.
Therefore, groundwater contamination is a major public health and environmental concern
in the coastal city of Lagos, partly because the majority of the population uses wells (either
boreholes or hand-dug) for drinking and domestic purposes.
Quaternary geology of the area comprises the Benin Formation (Miocene to Recent),
recent littoral alluvium and lagoon/coastal plain sands (Jones & Hockey, 1964; Durotoye,
1989; Longe et al., 1987). Lagos metropolis is underlain by a 3-layer aquifer system
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Urban groundwater management and protection 239
Figure 6. Map of densely populated Lagos (the names represent the densely populated areas &
numbers indicate wells sampled for water quality see later).
with varying hydrogeological properties and homogeneities. The aquifers have variable
thickness with the first and third horizons attaining thickness of approximately 200 m
and 250 m respectively at Lekki peninsula while the second horizon attains a thickness
of about 100 m at Ijanikin (Asiwaju-Bello & Oladeji, 2001). About 75% of groundwater
abstractions for domestic and industrial purposes in Lagos are obtained from the second
aquifer. Transmissivities range from 100 to 500 m2/d and average storage coefficient of
approximately 0.003 have been estimated for the first aquifer horizon (Asiwaju-Bello &
Oladeji, 2001).
2.6 Lusaka
Lusaka, the capital city of Zambia, is located on a wooded ridge, which runs from south-east
to the north-west. The location of Lusaka for a new capital city of the then Northern Rhodesia
was chosen after many years of debate and after examination of a number of possible
locations, including Chilanga, Broken Hill (now Kabwe), and four Copperbelt towns.After
ascertaining that there were adequate groundwater supplies, Lusaka was chosen partly to
avoid domination by the mining companies on the Copperbelt and partly because of its
location at the intersection of the main route network. It was inaugurated the new capital
city of Northern Rhodesia on May 30, 1935.
Settlement and development patterns in Lusaka have been greatly influenced by the
growth of population. With a population of only 195,753 at independence in 1964, there
have been progressive increases in population over the years, rising to 535,850 in 1980
and 769,353 in 1990 (CSO, 1990). In 2000, the population of Lusaka reached 1.2 million,
and is estimated at 2 million in 2007. Other than the high birth rate (3%), the drive for
most of this population has been the rural-urban migration in search of employment and
better livelihoods. Consequently, Lusaka has experienced rapid population growth and
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Figure 7. Geology and location of private and public water supply boreholes over the Lusaka aquifer.
uncontrolled rates of urbanisation (Figure 7), which has been a recipe for the mushrooming
of informal high-density settlements and the sprawling of unplanned low-density residential
settlements. The rapid growth of population in Lusaka has mismatched the development of
infrastructure.
Rocks underlying the city of Lusaka consist of schists interbedded with quartzites and
dominated by thick and extensive sequences of marbles (Figure 7). Available borehole
drilling data indicates carbonate rocks extending to depths in excess of 100 metres with
variations in the fracturing intensities (Nkhuwa, 1996). While some of the solution features
my not show any evidence of occurrence at the surface, they have great lateral extents in the
subsurface, with some of them having been intersected in boreholes at depths in excess of
60 m below ground surface. The presence of these features has transformed these rocks into
a favourable and comparatively cheap source of water supply to the city and they appear to
have exerted a lot of control on groundwater flow in the aquifer. Further, the occurrence
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Urban groundwater management and protection 241
and orientation of these fractures have dictated the general course of groundwater flow in
the aquifer.And an evaluation of water strikes in boreholes is indicative of their close asso-
ciation with discontinuities in the rock mass. The marbles have an average transmissivity of
approximately 600 m2/d. Thus, the hydrogeology of Lusaka indicates that the aquifer has
the best groundwater potential to support the city water supply for large-scale exploitation
if well managed.
Currently, rapid growth of population in Lusaka has outstripped the rate of provision
of basic social goods as well as adequate sanitation services. Peak water demand to cope
with current requirements estimated at an average per capita consumption of about 200
litres per day stands at about 400,000m3per day for a population that was estimated at
two million in 2007. Measured against actual daily production of about 200,000m3per day
currently supplied by the water authority, the deficit in supply raises conspicuous concern.
The current unsatisfied water demand has triggered a process of indiscriminate borehole
drilling (Figure 7) and excessive abstractions of groundwater from the aquifer.
3 STATUS OF URBAN GROUNDWATER IN SUB-SAHARAN AFRICA
Urban groundwater development in sub-Saharan Africa (according to Taylor et al., 2004)
can be categorised into (i) low-intensity abstraction (<0.2l/s) and high-intensity abstrac-
tion (>2 l/s). The high-intensity groundwater abstraction category is less common and
is for piped supplies, usually achieved using wellfields consisting of one or more high-
yielding boreholes equipped with motorised pumps. Low-intensity groundwater use occurs
via manually pumped boreholes and shallow wells, and is often private and unregulated.
The examples introduced aboveare used to discuss the impact of urbanisation. A summary
of the case studies is given in Table 1.
3.1 Recharge
The impact of urbanisation is not only viewed in terms of groundwater abstraction but
as it affects recharge. The general concept of urbanisation in this regard is that it reduces
recharge by water-proofing surfaces (Lerner & Barret, 1996; Barret, 2004), but the network
of water-carrying pipes under most of African cities are leaky, sometimes old and rusty. This
in addition to leaking sewers, septic tanks, storm drains constitutes high potential for urban
recharge (Table 2). According to Krothe et al. (2002), sewer lines are designed for leakage
(typically about 10%). In Cape Town, it is said that nearly 40% of the water from the supply
dams to consumers are lost through pipe bursts and leakages (comparable to 30% of recharge
from utility system leakage in San Antonio (Sharp et al., 2000); 12% in Austin, Texas
(Lorenzo-Rigney & Sharp, 1999)). Although few quantitative data are available, the general
belief is that much water is lost through the supply mains and distribution channels. Esti-
mates of water main leakage in urban areas are presented inTable 3. This loss, coupled irriga-
tion of farmlands and gardens in most of African cities, contributes significantly to recharge.
Generally, the quantification of natural recharge can be subject to a whole range of
difficulties; no clear methodologies; data deficiencies, and the resultant uncertainties that
may be relate to: (i) wide spatial and temporal variability in rainfall and run-off events;
(ii) lateral variation in soil profiles and hydrogeological conditions. These constraints
notwithstanding, estimates based on available data are useful for initial management
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Table 1. Summary of groundwater status of selected cities in SSA.
Urban area Addis Ababa Abidjan Cape Town Dakar Lagos Lusaka
Main Multilayer Unconfined Unconfined sand (semi- Semi-confined basalts Thick sands and gravel; Unconfined sands and
aquifer volcanic rocks Quaternary confined in places), and unconfined sands deeper confined sands gravels; Karstified
type deposits Fractured sandstone and gravels marble aquifer.
Aquifer Low in N Moderate, Moderate but towards Low with increasing Moderate with increasing n.a.
storage and central but progressive margins increases salinity from the NE salinity towards the west
part of the degradation of salinity towards the NW. margins
city and high the quality
in E and S from S
Average 1150 mm/a 1600 mm/a 600 mm/a 485 mm/a 1700 mm/a 900 mm/a
rainfall
Source of Rainfall and Mainly rainfall Mainly rainfall, Mainly rainfall Excess of rainfall, canal Mainly rainfall, but
primary dams periodic infiltration and riverbed infiltration with a substantial
recharge of runoff contribution from
water utility supply
and sewer leakage
Aquifer There is potential Not currently 0.133 m/a (from Few data, probably Currently, not
depletion depletion in quantified but model calculation) averaging 0.5m/a quantified
the southern modelling
part of the city projection
shows 0.33 m/a
Sanitation Extremely high Extremely high Very high in shallow Very high Very high in both Very high arising from
risk aquifers; threatens shallow and deep use of onsite sanitation;
deeper fractured aquifers indiscriminate disposal
aquifers of various forms of
solid wastes
Land Very low Low Generally Low Fairly low hazard Would have been quite
subsidence low hazard but growing concerns high, save for the
consolidation of soils
filling solution channels
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Urban groundwater management and protection 243
Table 2. Sources of aquifer recharge in urban areas with implications for groundwater
quality (Foster et al., 1996).
Recharge source Importance Water quality Pollution indicators
Leaking water mains Major Good Generally no obvious
indicators
On-site sanitation Major Poor N, B, Cl, FC
systems
Leaking sewers Minor Poor N, B, Cl, FC, SO4
(industrial chemicals)
Surface soakaway Minor to major Good to poor N, Cl, FC, HC, DOC
drainage (industrial chemicals)
Seepage from canals Minor to major Moderate to poor N, B, Cl, SO4, FC, DOC
& rivers (industrial chemicals)
B – Boron Cl – Chloride and salinity in general
DOC – Dissolved organic carbon (organic load) FC – Faecal coliforms
N – Nitrogen compounds (nitrate or ammonium) SO4– Sulphate
Table 3. Estimated leakage rates for municipal water in
selected cities.
Urban area Estimated water Estimated increase in
main losses (%) recharge (mm/a)
Addis Ababa 55 150
Abidján 40 100
Cape Town 40 30
Dakar – 34
Lagos 45 240
Lusaka 55 140
decisions. Sufficient efforts are however needed to monitor and analyse aquifer response
to medium-term abstraction in order to be able to refine the initial estimates of recharge.
3.2 Impact of urbanisation on groundwater quality and quantity
The main man-made impacts on groundwater in the various cities under consideration result
from urbanisation and from changes in land use. Some of the changes over the years include:
(i) clearing of bushland and shifting of vegetated areas to residential use; (ii) developing
agricultural, industrial and residential uses in undeveloped sections of the coastal cities;
(iii) increasing and high growth rate of urban population; (iv) high rural-urban migration.
The ever-increasing growth in urban population in sub-Saharan Africa since 1950s has been
analysed by Harris (1990) and illustrated in Taylor et al., (2004). Providing safe drinking
water supply; treatment of domestic and industrial wastewater; and management of solid
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244 Applied groundwater studies inAfrica
waste generated in the cities of Africa, will be some of the major challenges for urban
planners, policy makers, politicians and social workers.
Typical situations of water pollution in the urban settlements of SSA arise due to:
pollution of surface water by industrial effluents discharged into rivers or streams and
pollution of groundwater by leakages and spills from industries;
pollution of surface water by storm water, untreated sewage and wastewater, flowing
from an urban agglomerate, into a river or stream;
pollution of surface water by residential and industrial development in the vicinity of a
reservoir, river or canal supplying water to an urban area; and
pollution of groundwater in shallow aquifers due to leakage from septic tanks, soak pits
and sewage lines of urban areas, and also from influent seepage from rivers/streams
carrying polluted surface water.
Often urban groundwater use can lead to over-exploitation and consequent problems such
as saline water intrusion. Examples include the south coast of Lagos, Dakar, and Cape Town.
Groundwater quality is usually worse beneath cities than beneath nearby rural areas.
3.2.1 Lagos
During a comprehensive groundwater-quality study for the south-eastern part of the city
of Lagos (1999–2001) groundwater samples from existing wells were analysed for many
parameters (Adelana et al., 2003, 2004, 2005). Urban impact is indicated for more than 60
percent of all samples by high concentrations of sulphate, nitrate (with NH4-N in places)
and chloride (Figure 8).
The mean nitrate content in groundwater in Lagos area is 70.3 mg/l; 60% have NO3
content above the WHO guideline of 50 mg/l. The groundwater is Lagos is particularly
vulnerable to contamination since groundwater is shallow, and the aquifer unconsolidated
permeable sand and gravel. The concentration of nitrate measured in rainwater shows
clearly that NO3is introduced into groundwater through urban activity, and most likely on
site sanitation, rather than through a natural source. The fast rate of urbanisation in Lagos
has brought most of the industrial layout, farmlands and swamps within residential areas.
3.2.2 Addis Ababa
A study of groundwater-quality for Addis Ababa included sampling of several observation
and production boreholes and springs (Alemayehu et al., 2005). The results revealed that
the nitrate concentration ranged from 0.72 mg/l to 728 mg/l in groundwater and springs
(Alemayehu, 2001). Other indicators of pollution are the occurrence of nitrogen as NH4
and/or NO2and coliform bacteria. The concentration of total coliforms and E.Coli in the
groundwater system showed large seasonal variations (Alemayehu et al., 2005). Groundwa-
ter contamination problems in AddisAbaba are mainly related to poor borehole construction
and leakage from defective sewerage lines and septic tanks.
3.2.3 Abidjan
During a 3-year assessment project on the pollution status and vulnerability of the Abidjan
aquifer, there was a clear indication that the groundwater of Abidjan is affected by the
progression of pollution from the south towards the north and east (Jourda et al., 2006).
The major pollution threat to the Abidjan aquifer is sewage: there are no developed network
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Urban groundwater management and protection 245
Figure 8. Water quality in shallow wells in Lagos (a) plot of Cl, SO4and NO3in groundwater versus
the depth of borehole; (b) Nitrate concentrations of groundwater in hand-dug-wells.
of systems for the collection of waste and wastewater. This led to high nitrate concentra-
tions (commonly 100–300 mg/l, maximum 500 mg/l as NO3) in water supply boreholes
(1994–2004) with cholera cases between 2001 and 2003 being attributed to contaminated
groundwater (Jourda et al., 2006).
3.2.4 Cape Town
In Cape Town the need to augment the present water supply through additional borehole
drilling is expected to put more pressure on the groundwater resources in the area. Data
from 20 boreholes located in the area show elevated Cl, Na, and total dissolved solids (TDS)
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246 Applied groundwater studies inAfrica
associated with saline intrusion. Chloride concentrations between 1500 and 2000 mg/l are
recorded in some boreholes (Adelana & Xu, 2006).
Within the Cape Municipality, the size, density and location of settlements have been
found to determine the degree or intensity of pollution (DWAF, 1999).The various sources
of pollution have been classed according to the varying human activities (Adelana & Xu,
2006). Significant sources of contaminants in and around the city of Cape Town is from
leakage of underground storage tanks for petrol and diesel, nutrients and pathogens in
human wastes (e.g. nitrate, phosphate, potassium), cyanide and trichloroethene (TCE)
from metal plating industry, chemicals used for cleaning and agrochemicals (fertilizers and
pesticides). General findings around the city of Cape Town are the high concentrations of
phosphorus (>7.5 mg/l), ammonium (200 mg/l as N) found in the vicinity of the unlined
sludge ponds (Usher et al., 2004), cyanide (15–210 mg/kg in soils), and TCE (6–4089 µg/l)
from unlined sewage sludge drying ponds and sludge spills on the unconfined, primary
sand aquifer (Parsons & Taljard, 2000).
3.2.5 Dakar
The urban aquifer of Dakar contains nitrate concentrations that exceeds the standards of
50 mg/l. Monitoring boreholes revealed up to 300 mg/l as NO3in the unconfined aquifer
to the eastern suburb of Dakar (Deme et al., 2006). Earlier chemical data of the aquifer
and spatial distribution of nitrate contamination showed up to 540 mg/l NO3(Cisse et al.,
2000).The high nitrate concentrationsarerelated to the rapidpopulationgrowthin this urban
setting. Investigations have indicated that nitrate concentrations are increasing steadily in
the densely populated zone (from Pikine to Thiaroye andYeumbeul) from 26.7 mg/l in 1967
to 804 mg/l in 2004 (Deme et al., 2006; Cisse et al., 2004). This widespread pollution is
caused by the inadequacy of sanitary installations and garbage collection infrastructure in
the densely populated of Dakar (Deme et al., 2006).
3.2.6 Lusaka
In Lusaka, four sampling campaigns undertaken in mid-November 2003 (before the onset
of the rainy season), March 2004 (during the rainy season), October 2004 (at the peak of
the dry season) and March 2005 (during a drought period in the rainy season) revealed the
variability of pollutant loading with the varying levels of the water-table (Nkhuwa, 2006).
Faecal contamination increases with the rise in the water-table levels. Consumption of such
water, which is usually of unfavourable quality, has heightened outbreaks of waterborne
diseases, such as cholera and dysentery that have been experienced in many areas of the city.
In Lusaka groundwater mining and drought episodes appear to have resulted in a pro-
gressive decline in the aquifer water-table (Figure 9) because of groundwater withdrawals
is far in excess of the average rates of annual recharge. Such declines in the water-table lead
to reduced borehole yields, which provoke an expensive and inefficient cycle of borehole
deepening to regain productivity, or even premature loss of investment due to forced aban-
donment of boreholes. Progressive lowering of the water-table will undoubtedly increase
production costs,thereby imposing restricted access of the resource to the low-income group
of the city population, whose shallow wells may dry up.
High-density settlements have the highest growth of population in the city. Unfortunately,
these areas rely solely on pit latrines to dispose of their excreta, while shallow wells have
provided the most common sources of water supply. Most of the settlements have flourished
over the aquifer recharge areas where there is indiscriminate disposal of different forms
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Urban groundwater management and protection 247
Figure 9. Fluctuations of the water-level in response to pumping and drought (After Nkhuwa, 1999).
Annual fluctuations are superimposed on a long-term decline.
Figure 10. Photographs showing different forms of waste dumped in informal waste sites around
Lusaka.
of solid wastes in solution features in karstified marbles underlying the city (Figure 10).
Consequently, these practices pose serious risks to the potability of water in sufficient
quantities to support socio-economic development of Lusaka’s residents.
Another major consequence of the limited planning capacity and the ensuing unplanned
settlements in Lusaka has been the settlement into areas that were previously considered
unsuitable for habitation because of the high water-table. Most of the settlements use
either pit latrines or septic tanks to dispose off excreta, while also heavily dependent on
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248 Applied groundwater studies inAfrica
Figure 11. The distribution of excreta disposal points and shallow wells in some high-density
townships of Lusaka (after Nkhuwa 2006).
groundwater obtained from private sources lying in close proximity to the pit latrines
(Figure 11).
4 HISTORYAND CURRENT GROUNDWATER MANAGEMENT PRACTICES
4.1 Addis Ababa/Ethiopia
The water management practice in the city of Addis Ababa is handled by the Addis Ababa
water and Sewerage Authority. TheAuthority provides clean water both from surface water
and groundwater sources. In the outskirts of the city four water reservoirs were built for
water supply purposes. Gefersa, Legadadi, and Dire reservoirs are the most important sur-
face sources. Gefersa was the first dam built in 1944 about 18 km west of Addis Ababa.
At present the dam has a reservoir capacity of 6.5 Mm3and the maximum capacity of the
treatment plant is 30,000 m3/d. Due to rapid growth of the population and expansion of the
city from year to year, there is a serious shortage of water in different parts of AddisAbaba.
To alleviate the problem Legedadi and Dire dams were built in 1970 and 1999, 33 km east
of Addis Ababa. The treatment capacity of Legedadi plant was upgraded from 50,000 m3
to 150,000 m3per day. The Dire dam supplies 42,000 m3per day for Legedadi plant, since
1999.
Groundwater abstraction fromAkaki well field was fixed (based on modelling results) at
35,000 m3/d for a 20-year period; other municipal boreholes account for 10,000 m3/d. Other
private and governmental institutions tap as much as 50,000 m3/d from groundwater. Water
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Urban groundwater management and protection 249
quality monitoring is carried out regularly before supply. However, there is no adequate
legislation to guide management practice in the city.
4.2 Abidjan/Cote D’Ivoire
In Cote D’Ivoire there is no overarching institutional framework governing water resources
management. Water resources are managed by several institutions ranging from state min-
istries, private companies/organisations, universities and research institutes.This conforms
to a partitioned organisational model (Jourda et al. 2006), with three groups (MinistryA, B,
C), each with specialised structures. Interestingly, these structures work without systematic
coordination with no joint actions in the management of water supply aquifer, particularly
in Abidjan, and no synergy between the structures. These pose serious management prob-
lems for the Abidjan aquifer with consequent deterioration of water quantity and quality.
According to Jourda et al. (2006) reforms have nowbeen undertaken which have led to the
establishment of the Ministry of Water and Forestry, with responsibility for the supervision
and implementation of national policies on water.
4.3 Cape Town/South Africa
South Africa now has progressive water legislation and a sophisticated water resources
management; adequately catered for under the National WaterActs of 1998. Under the Act,
water is recognised as a national asset, and this permits its transfer from where it is available
to where it is inadequate for the benefits of the populace. The previous Water Act linked
access to water to land ownership. In both Act No. 108 of 1996 and Act No. 36 of 1998,
the management of water resources is an exclusively national issue. The National Water
Act 1998 mandates the Minister of Water Affairs and Forestry to ensure that water is pro-
tected, used, developed, conserved, managed and controlled in a sustainable and equitable
manner for the benefit of all persons. The National Water Resource Strategy (NWRS) is
focused on the sustainable use of both surface and groundwater resources. This includes the
following:
develop appropriate, achievable and easily implementable policies and systems;
provide simple, efficient and effective procedures and guidelines;
adopt a total systems approach to water resource management in the development of
policy;
effective and focused protection interventions will be facilitated by a differentiated
approach, based on a system of resource classification designed specifically for
groundwater resources.
Determining the practicable level of protection necessary for individual groundwater
resources will take account of a number of factors as described in the Act.Aquifers which
represent the sole source of water for communities will be afforded special status, and will
enjoy the highest level of protection.
In Cape Town, as in most SouthAfrican cities where there is a growing water requirement,
demands are met by the development and utilisation of surface water (through construction
of more dams and weirs); water resource management interventions such as diversions,
storage and inter-catchment transfer of water is common practise. These impact on water
quality and also can leave groundwater under-utilised. Optimal utilisation and management
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250 Applied groundwater studies inAfrica
of groundwater resources will require improved capacity to assess groundwater potential
and monitor trends, and a better understanding of aquifer functioning.
4.4 Dakar/Senegal
Water resources in Senegal are regulated by Law No. 81-13 of March 4, 1981, which gives
ownership of the resource to the state (Law 81-13, art 8, Senegal Constitution adopted
2001). The preamble of the statutory framework defines water rights and the manage-
ment of water resources (Salman & Bradlow, 2006). After the Sahelian drought of the
1970s the ‘Organisation pour la Mise en Valeur du Fleuve Sénégal’ (OMVS) was cre-
ated. A pilot study funded by the Japan International Cooperation Agency (JICA, 1999)
examined the potential for self reliance and community management. Rural residents suf-
fered from drying wells in Senegal during drought. JICA (with the local authorities) has
constructed deep boreholes and water supply facilities at 109 locations in rural areas.
However, problems arose afterwards due to the lack of appropriate maintenance and man-
agement. This new assistance aims to improve the management capacity of the community
water management cooperative including financial independence. The cooperative, as an
organization run with the participation of local people, strives to select their members
democratically and to increase the transparency of their operations by through information
disclosure.
In Dakar, new strategies are in place to develop rainwater harvesting. The new approach
preserves rainwater by increasing the rainwater infiltrating rate in the dune sands through
artificial recharge (Dasylva et al., 2004). This management measure allows the lowering
of the run-off volume and favours the increase of groundwater replenishment.
4.5 Lagos/Nigeria
Management of water resources in Nigeria has led to the establishment of several bod-
ies/organisations in the past. Some of these were short-lived and closed abruptly without
achieving the desired goal (usually as a result of the nation’s political instability) while
others were crippled by a lack of organisation and vision-oriented leadership or coordina-
tion. According to Akujieze et al. (2003) there are about 11 independent bodies charged
with water resources management issues. The River Basin Development Authorities, for
example, were established by the Federal Government of Nigeria in 1977 with emphasis
on the concept of River catchment as a water resource management unit.
Nigeria’s water legislation came in a decree referred to as Decree 101 of 1993. Although
this was set out as a water resources development and management law it has little reference
to groundwater. The requirements of Decree 101 of 1993 have stimulated investigations
such as impact assessments of waste disposal sites on groundwater quality. These inves-
tigations are aimed at existing, or recognised potential problem sites but are often only
‘token’ investigations carried out by companies or corporations, to meet their obligations
under the Federal, States and Local Governments conditions of award of contracts. Nigeria
has no standards for the evaluation of existing landfills or the investigation of potential
new sites. In some cases, it is also difficult to find the party responsible for degrading
the resource or it is difficult to get such a party to assume liability. This alone empha-
sizes the need for a proactive approach to assess groundwater vulnerability under present
conditions.
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Urban groundwater management and protection 251
National plans and rules are to assist Local Government or Municipal Councils to carry
out their functions relating to resource management. Unfortunately, this is still a game of
chance under the present water management policies in Nigeria. There is need to restate
and reform the law relating to the use of land, air, and water. This will help to promote
the sustainable management of natural and physical resources, including groundwater.
‘Sustainable management’ must ensure that resources are sustained for future generations
and adverse environmental effects are avoided, remedied, or mitigated. Therefore, it is the
responsibility of the national and regional water councils to implement the water legislation
or Decree 101 and incorporates aspects relating to management of groundwater or prevents
groundwater contamination based on current scientific evidence.
4.6 Lusaka/Zambia
The Lusaka aquifer is generally characterized by shallow water-tables, a thin cover of coarse
soils with low clay contents, unconfined conditions, and a flat topography. These factors
generally facilitate increased recharge for an aquifer littered with pollution sources over its
recharge areas. In this context, aquifer protection becomes very difficult. Consequently,
aquifer protection in Lusaka has become very reactive as it continues to emerge in response
to aquifer contamination resulting from human activities in the recharge zones. In other
words, efforts in the protection of the aquifer have not attempted to prohibit any potentially
contaminating development within the cone of depression of each borehole. This occurred
because, in its current state, the Zambian Water Act neither regulates drilling of boreholes
nor pollution of groundwater resources.
The Water Act – Cap 198 of the Laws of Zambia was passed by the Legislative Council
of Northern Rhodesia in 1948 as the Water Ordinance, and came into force in 1949.After
independence in 1964, the Water Ordinance was revised and transformed into an Act of
Parliament – the Water Act. The Water Act has been amended 10 times, the last being
Act. N.13 of 1994. Recognising these deficiencies, the Zambian Government embarked
on the formulation of the new Water Bill, which is currently in its draft form. The Draft
Water Bill seeks to address the deficiencies of the Water Act – Cap 198 of the Laws of
Zambia, with a view to providing a framework that promotes Integrated Water Resources
Management through: (a) Establishment of a national monitoring and information system,
(b) Establishment of hydrological stations.
Parts VII and VIII of the Water Bill deal with regulation on the drilling of bore-
holes and preservation of good quality national water resources, respectively. However,
any groundwater protection measures to be adopted in Lusaka must accept the fact that
existing infrastructure and anthropomorphic activities cannot be moved, although they
cannot be ignored. In this regard, the main route of aquifer protection in Lusaka must
be proactive/preventive. Clearly, this route would be preferable as it tends to promote
contaminant-free water sources. The latter represents the cheaper option since treatment
costs becomes lower.
Further, due to reasons of economics and inadequate public awareness, it may be very
difficult, if not impossible, to force changes in landuse practices in pursuit of aquifer-
wide protection strategies. In order to assess the effectiveness of any protection measures
instituted in Lusaka, it is strongly recommended that a monitoring system for a range of
physico-chemical and microbial parameters be instituted. This will give an early warning
of any contaminant event likely to occur in the aquifer or part thereof.
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252 Applied groundwater studies inAfrica
Table 4. Sub-Saharan African cities’groundwater condition.
City Country Information Role of groundwater Groundwater
status problems
Addis Ababa Ethiopia 1 Major urb poll
Abidjan Cote D’Ivoire 2 Major ss, urb poll, gwl
Cape Town South Africa 1 Minor urb poll, d-s poll
Dakar Senegal 2 Major ss, urb poll, sal int
Lagos Nigeria 2 Majorurb poll, sal int
Lusaka Zambia 3 Major urb poll, gwl
1 Full survey data ss – sole source of water supply
2 Useful summary document urb poll – Groundwater pollution within
3 General background only urban area
major – Major source of public water supply sal int – Aquifer saline intrusion
minor – Minor source of public water supply d-s poll – downstream groundwater pollution
but high potential for future supply gwl – falling groundwater level
major– Major private domestic/industrial use
5 GROUNDWATER MANAGEMENT CHALLENGES AND PROTECTION
STRATEGIES
Unrestricted use of groundwater through boreholes will result in a lowering of the water-
table in many cities/urban centres and intrusion of saline water in coastal areas of SSA.
The crucial issues of management of groundwater requires adequate planning and direc-
tion from hydrogeologists and a reasonable level of hydrogeological awareness amongst
water managers, supply engineers, farmers and local villagers who may be responsible for
managing abstraction and monitoring. It has once been suggested that part of the manage-
ment cycle in SSA should incorporate monitoring data, learning and feedback to improve
the understanding of the resource under extreme conditions (Colvin & Chipimpi. 2004).
The key challenge is developing capacity to manage and monitor intensive groundwater
use in our urban centres. Appropriate technology and sustainable financing are also critical
management constraints.
Furthermore, the present legal and jurisdiction framework for groundwater management
is fragmented, inconsistent and incomplete. Groundwater management practises vary from
region to region, and in some cases, do not exist at all. This is a long-standing problem
in SSA, and as such requires a framework of collaboration on groundwater studies. Such
collaborative efforts should focus on providing basic geological and groundwater data
essential to manage groundwater resources in SSA.
Part of the challenge will be to develop locally appropriate groundwater protection plans
for the cities; even with the limited resource and knowledge base in SSA. There is also a
need for stakeholder consultation to contribute to the development of policy options for
aquifer protection in respective cities of SSA. Table 4 shows the groundwater-dependent
cities considered in this paper, and whose groundwater information/condition could be
useful in formulating policy strategies.
In the present condition, any set of aquifer protection policies to be applied to an already-
existing urban area will need to evolve strategies which, while they constrain land-use,
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Urban groundwater management and protection 253
accept trade-offs between competing interests and utilise the natural contaminant atten-
uation capacity of the strata overlying aquifers (Matthess et al., 1985). In any case, to
successfully implement such strategies hydrogeological understanding needs to inform
land-use policies and provide simple robust matrices that indicate what activities are pos-
sible where, at an acceptable risk to groundwater. In turn, construction of such matrices
requires pragmatic design criteria if planning is not to be so delayed as to irretrievably
prejudice resource sustainability. In many cases important and influential stakeholders
involved in urban water management decisions do not have a technical background either
in engineering or in resource planning. Professional hydrogeological expertise in city water
management is generally absent, and municipal water supply utilities may be more focussed
on day-to-day operational needs of the present system, even where groundwater is a major
urban resource.
5.1 Addis Ababa, Ethiopia
The main problem is lack of implementation of the current Environmental management
plan to control surface water and groundwater from pollution. The concerned bodies are
striving to implement the plan through community participation and by imposing laws.
In an effort to fulfil the growing water demand the city is increasingly relying on sup-
plies from groundwater sources such as the Akaki Well field, which requires a delicate
aquifer management strategy to avoid over-abstraction. There is also continuous effort by
the municipality to establish new well fields to fill the existing gap.
The growths of towns have had profound effects on the groundwater resources due to
poor land use and waste disposal and sanitation practices. Population growth rate in Addis
Ababa, estimated at 4% has moved at a higher pace than the ability of the government to
provide the necessary infrastructure to handle domestic and industrial effluents and this
has lead to widespread contamination especially of shallow groundwater. Due to the above
challenges protection of groundwater in terms of quality and quantity is needed in order
to avoid reduction in available groundwater resources, escalating water supply costs and
potential impacts on human health.
5.2 Abidjan, Cote D’Ivoire
The problem of groundwater management in Cote D’Ivoire begins with poor organisational
structure, where water resources are managed in a sectarian manner and a single policy of
resource management. In reality the decision-making centres are varied and often antago-
nistic one to another (Jourda et al., 2006). Factors contributing to poor management are:
absence of a well-coordinated institutional framework governing water resources in Cote
D’Ivoire; lack of proper dissemination of information to users of the resource; the lack
of respect to public property; poor sanitation and waste collection network; increasing
water demand (resulting from high population growth); and decrease of recharge (due to
climatic variations). The growth of population (up to 3.7% in 10 years), increased agricul-
tural and industrial practices of this area have resulted in an increasingly demand for water
from the Abidjan aquifer and posing greater challenge (Issiaka et al., 2006; Jourda et al.,
2006). Management policies are rare and the lack of cooperation among various institutions
responsible for resource management further heightens the problem.
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254 Applied groundwater studies inAfrica
New groundwater management and aquifer protection strategies are proposed by Jourda
et al. (2006) and include: (i) creation of an institutional framework for integrated water
resources management in order to establish lawful measurements in the various application
of water protection; (ii) creation of synergy among the scientific community, the NGOs,
stakeholders and authorities charged with aquifer management in order to collect and dis-
seminate relevant information; (iii) identification of major pollution areas and threats to
water supply aquifer with the aim to draw attention of stakeholders and the general public to
mitigate such threats; and (iv) establish urban water quality monitoring in order to prevent
further pollution of the Abidjan aquifer.
5.3 Cape Town, South Africa
South Africa has in place a good management program for its groundwater resources.
However, the issue of protection of aquifers for the supply of good quality water require a
more pragmatic approach. A systematic approach was neglected in the past as a result of
its “private water” status under the previous legislation, and relatively little was invested in
comprehensive resource assessment (DWAF, 1999).
The overall quality of groundwater in the greater Cape Town area is good enough to
warrant its full development and utilisation in the water supply augmentation scheme for
the City of Cape Town Municipality. However, occurrence of pollution from present and
previous studies as highlighted earlier in this paper and the identification of point- and non-
point sources calls for groundwater protection. The establishment of site specific protection
zones, with regulation of land use within them and the Resource Directed Measures (RDM)
under the South AfricanWater Act of 1998 has been seen as a possible way forward in future
groundwater management in South Africa.Through research and development investment
in the past five to ten years it has become clear that groundwater in usable, if limited,
quantities can be found in many places with the appropriate expertise. Deep drilling has
shown the potential for large-scale development of groundwater in some areas such as
those underlain by the Table Mountain Group geological formations. With a focus on the
development of local resources groundwater’s role in reconciling future demand and supply
could rise significantly, and meeting relatively small water requirements from groundwater
would be especially attractive.
5.4 Dakar, Senegal
Water resources management in Senegal is a crucial issue; explosive population growth and
economic development have exacerbated and expanded the range of water-related problems,
such as shortages of supply and pollution. Groundwater is abundant in Senegal except for
Tambacounda region. Major constraints for the use of the groundwater are the lack of
precise data on aquifers such as capacity, depth, contamination and so on. Groundwater
is a crucial resource for future development in Senegal. Therefore, certain policies and
strategies to sustain the development and management of groundwater resources will have
to be elaborated through series of studies to secure safe water supply.
Future challenges to water resources management in Dakar include pollution and man-
agement of wastes. The amount of solid waste generated annually throughout the country
is estimated to be 744,250 tons of which 280,000tons are generated in Dakar (JICA, 1999).
5% of Dakar’s population has no access to any sanitation facilities. 40% of households
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Urban groundwater management and protection 255
in urban area have water in their houses, 50% have access to a public water tap, and the
remaining depends on wells.
At present, household waste is collected by metal containers and transported to the
dumping site. The number of containers has increased in major cities but the waste collection
service is not yet regularized because of the lack of finance and capacity of the organization.
According to JICA report, collection vehicles cannot reach to the collection sites because of
narrow streets or unpaved road.A significant proportion of household waste in urban area
is still uncollected and remains in the streets, open canals or illicit dump sites. Untreated
wastewater flows directly into rivers (JICA 1999).
5.5 Lagos, Nigeria
Even though the demand for groundwater is becoming higher in both rural and urban
centres in Nigeria, yet the management of the aquifers or wellfields is not closely moni-
tored. In Lagos metropolis, in particular, careful management is required to avoid further
degradation of groundwater quality. There is need to maintain a groundwater quality mon-
itoring network to characterize groundwater quality and investigate trends. Point-source
discharges and significant use need to be regulated through conditions for consents and
regional rules to ensure sustainable resource management. National or regional codes of
practice for managing non-point sources and commitment to environmental education as a
means for managing groundwater quality are further required on the part of the government.
For municipal water supply, high and stable raw-water quality is a prerequisite, and one
best met by protected groundwater sources.
Vulnerability assessment is little known or researched in Nigeria. With many surface
waters now polluted, the importance of groundwater as a source of drinking water has
to increase. While regional plans and rules exist to protect surface waters, groundwater
protection is in its infancy in Nigeria, and is regarded as inadequate. Water resources
legislation is in existence but it’s impart is yet to be felt in terms of true ownership and
usage of the nation’s water resources. The reasons for these are obvious. For example, the
Decree 101 and water-related regulations are based on mainly on socio-economic factors
and not necessarily on scientific research such as, groundwater vulnerability or aquifer
sensitivity. Federal, States and Local Government programmes need to be criticized for not
formulating or implementing policies on on-site effluent disposal.
Emphasis is here placed on groundwater protection in order to prevent deteriorating
conditions of the main aquifers in Nigeria. The assessment of aquifer vulnerability and
sensitivity to pollution on a national scale is very necessary in Nigerian urban centres under
the present conditions. The most important potential use of aquifer protection is in raising
public awareness which, in turn, may result in positive reactions or more informed land
use decisions. Aquifers with high sensitivity should be monitored closely while aquifers
with low sensitivity may not require detail monitoring. In addition, permits or consents for
environmental activities should have more demanding conditions imposed on them in areas
of high as opposed to low sensitivity.
5.6 Lusaka, Zambia
The presence of a well developed system of conduits, solution channels and subter-
ranean cavities in the Lusaka aquifer(s) reduces and/or completely eliminates the natural
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256 Applied groundwater studies inAfrica
attenuation of pollutants through dilution and natural filtration. Therefore, the absence of
legislation to limit or inhibit human activities on the aquifer recharge areas pose great risk
of groundwater pollution and rendering it unusable for any purpose.
Qualitatively, the quality of most physico-chemical and bacteriological parameters over
most of the aquifer show a general decrease from the dry season into the wet season.This is
probably resulting from dilution arising from increased saturation in the aquifer. Therefore,
regular water quality monitoring from supply points for physico-chemical and microbial
parameters will give an early warning of any contaminant event likely to occur in any part
of the aquifer.This will allow timely action by concerned authorities to avert the possibility
of the population consuming water of insufficient quality.
The long-term deterioration of water quality, leading to progressively more costly water
treatment, is the inevitable result of current ad-hoc development reminiscent of a thriving
city of Lusaka located largely on a karstic aquifer. In the long-term, groundwater beneath
Lusaka is likely to become unfit for human consumption even with expensive treatment. In
which case, there will be need to look for new sources of water supply away from current
sources or a reconsideration of whether or not a new site should be sought for the city
(Mpamba et al., this volume).
6 FUTURE FOCUS OF URBAN GROUNDWATER MANAGEMENTAND
PROTECTION IN SUB-SAHARAN AFRICA
Groundwater is the preferred source for piped water supplies in many urban areas across
sub-Saharan Africa and its development is forecast to increase dramatically in an attempt to
improve urban water supply coverage. Heavy groundwater abstraction in some urban areas
has already resulted in lowering of groundwater levels and competitive pumping between
water sources. Similarly, poor landuse practices and onsite sanitation systems in the form of
septic tanks and pit latrines have caused contamination of groundwater resources in many
urban areas especially where the groundwater table is shallow. Concrete action in form of
improved management therefore needs to be urgently taken in a number of areas to mitigate
actual and potential derogation caused by excessive exploitation and inadequate pollution
control. Key areas where future action is required include: (a) further research on ground-
water occurrence and movement, (b) development of institutional frameworks for ground-
water management, (c) advocacy and raising awareness, (d) stakeholder involvement.
6.1 Research in groundwater occurrence and movement
Understanding the occurrence and movement of groundwater in urban areas is key to its
sustainable management and protection. Key information for guiding groundwater man-
agement and protection decisions is however unavailable in most places. The continued lack
of this information implies that decisions are either not made or have no good basis. It is
for example, not known how far water sources should be from each other and from sources
of pollution to avoid competitive pumping or pollution and this constrains decision making
regarding siting of various facilities. It is therefore necessary to carry out research to resolve
key hydrogeological questions related to protection of boreholes from competitive pump-
ing and siting, in relation to onsite sanitation systems, in various geological environments.
Availability of this information will make it possible to develop strategies and guidelines
for optimal groundwater development, management and protection in various settings.
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Urban groundwater management and protection 257
6.2 Institutional frameworks for groundwater management
While institutional frameworks for groundwater management exist in many national and
local level government institutions, these are not normally replicated in urban areas. Thus,
groundwater management and protection continues to be done in an adhoc manner, if
done at all. To improve this situation, institutional frameworks for groundwater resources
management in urban areas need to be developed.
6.3 Advocacy and raising awareness
Groundwater, in many places, is considered to be abundant due to its concealed nature, and
its susceptibility to pollution is not apparent. Thus, its management and protection often
do not attract attention from policy and decision makers, funding organisations, users and
other stakeholders. In view of the current and planned heavy abstraction of groundwater
in many urban areas, and the increase in pollution from various sources, it is essential that
advocacy and awareness raising programmes are instituted to ensure that the susceptibility
of groundwater to overexploitation and pollution is appreciated by all the stakeholders. This
will enable them to appreciate the benefits of groundwater management and protection and
ensure that appropriate actions are taken.
6.4 Stakeholder participation
Sustainable groundwater management and protection requires the active participation of all
stakeholders. Stakeholder participation is the process of involving those who are affected
by and thus have an interest in the management and protection of groundwater resources.
Groundwater stakeholders may be users of groundwater, or those who carry out activities
that could pollute groundwater, or those who are concerned with groundwater resources and
general environmental management. Participation of stakeholders in groundwater manage-
ment and protection is important for a number of reasons: it ensures that decisions regarding
groundwater resources exploitation are integrated and coordinated with landuse and envi-
ronmental management; it ensures that there is equity in allocation of groundwater resources
to various users; it enables better estimation of current and future demands for groundwater
resources; it can facilitate the optimization of groundwater use by competing users; it can
facilitate the implementation of strategies and decisions regarding sustainable groundwater
abstraction and protection; and it can enable active involvement of the stakeholders in data
collection and follow up monitoring and inspection of groundwater use and pollution.
REFERENCES
Adelana, S. M. A., Bale, R. B. & Wu, M. 2003. Quality assessment and pollution vulnerability of
groundwater in Lagos metropolis, SW Nigeria. In: Proceedings of the Aquifer Vulnerability Risk
Conference AVR03, Salamanca, Mexico, 2, 1–17.
Adelana, S. M. A., Bale, R. B. & Wu, M. 2004. Water quality in a growing urban centre along
the coast of southwestern Nigeria. In: Seiler, K. P., Wu, C. & Xi, R. (eds.) Research Basins and
Hydrological Planning. Balkema, The Netherlands, 83–92.
Adelana, S. M. A., Bale, R. B., Olasehinde, P. I. & Wu, M. 2005. The impact of anthropogenic
activities over groundwater quality of a coastal aquifer in Southwestern Nigeria. In: Proceedings
Adelana ch014.tex 17/4/2008 12: 14 Page 258
258 Applied groundwater studies inAfrica
of Aquifer Vulnerability & Risk, 2nd International Workshop & 4th Congress on the Protection
and Management of Groundwater, 21–23 September 2005, Reggia di Colorno – Parma.
Adelana, S. M. A. & Xu, Y. 2006. Groundwater contamination and protection of the Cape Flats
aquifer, South Africa. In: Xu, Y. & Usher, B. (eds.) Groundwater pollution in Africa, Taylor &
Francis, London, 265–277.
Akujieze, C. N., Coker, S. J. L. & Oteze, G. E. 2003. Groundwater in Nigeria – a millennium
experience – distribution, practice, problems and solutions. Hydrogeology Journal, 11, 259–274.
Alemayehu, T. 2001. The impact of uncontrolled waste disposal on surface water quality in Addis
Ababa. SINET: Ethiopian Journal of Science, 24, 93–104.
Alemayehu, T. 2006. Groundwater occurrence in Ethiopia. Addis Ababa University Press, Addis
Ababa, Ethiopia.
Alemayehu, T., Dagnachew, L. & Tenalem, A. 2005. Hydrogeology, water quality and the degree
of groundwater vulnerability to pollution in Addis Ababa, Ethiopia. UNEP/UNESCO/UN-
HABITAT/ECA publication, Nairobi, Kenya.
Asiwaju-Bello, Y. A. & Akande, O. O. 2001. Urban groundwater pollution: case study of a refuse
disposal site in Lagos metropolis. Water Resources, 12, 22–26.
Barret, M. H. 2004. Characteristics of urban groundwater. In: Lerner, D. N. (ed.) Urban groundwa-
ter pollution. IAH International Contributions to Hydrogeology, 24, Balkema, The Netherlands,
29–51.
CCT 2006. Annual Report 2005/2006. City of Cape Town.
Cissé, S. Faye, S., Wohnlich, S. & Gaye, C. B. 2004. An assessment of the risk associated with urban
development in the Thiaroye area (Senegal). Environmental Geology, 45, 312–322.
Cissé, S., Faye, S., Gaye, C. B. & Faye, A. 2000. Effect of rapidly urbanizing environment on the
Thiaroye, Senegal unconfined sandy aquifer. In: Silolo (ed.) Groundwater: past achievements and
future challenges, Balkema, The Netherlands, 719–723.
Colvin, C. & Chipimpi, B. 2005. Opportunities and challenges of intensive use of groundwater
in Sub-Saharan Africa. In: Sahuquillo, A., Capilla, J., Martinez-Cortina, L. & Sanchez-Vila,
X. (eds.) Groundwater intensive use. IAH Selected papers, 7, Balkema, The Netherlands,
147–156.
CSO 1990. Census of population, housing and agriculture 1990 – Prelim report. Central Statistical
Office, Lusaka, Zambia.
Dasylvia, S., Cosandey, C., Orange, D. & Sambou, S. 2004. Rainwater infiltration rate and ground-
water sustainable management in the Dakar region. Agric Eng International: CIGR Journal of
Scientific Research & Development, 6, 1–11.
Deme, I., Tandia, A. A., Faye, A., Malou, R., Dia, I. & Diallo, M. S. 2006. Management of nitrate
pollution of groundwater inAfrican cities: The case of Dakar, Senegal. In: Xu Y & Usher B (eds.)
Groundwater pollution in Africa.Taylor & Francis, London, 181–192.
Durotoye, A. B. 1989. Quaternary sediments in Nigeria. In: Kogbe, C.A. (ed.) Geology of Nigeria,
Elizabeth Press, Lagos, 431–451.
DWAF 1999. Water resources protection policy implementation, resource directed measures for
protection of waterresources, Integrated Manual, Department of Water Affairs and Forestry Report,
N/28/99.
Foster, S. S. D., Lawrence, A. R. & Morris, B. L. 1996. Groundwater resources beneath rapidly
urbanizing cities-implications and priorities for water supply management. In: Report of the
Habitat II Conference, Beijing, China, March 1996, 356–365.
Harris, N. 1990. Urbanization, economic development and policy in developing countries. Habitat
International, 14, 3–42.
INS 2001. Recensement General de la Population et de l’Habitation (RGPH) 1998. Domees socio-
demographiques et economiques des localites, resultats definifs par localites, region des lagunes,
3, National Statistics Institute of Ivory Coast, 43p.
Adelana ch014.tex 17/4/2008 12: 14 Page 259
Urban groundwater management and protection 259
Issiaka, S. Albert, Bi T, Ariiistide D.G. & Innocent K.K. 2006.Vulnerability assessment of the Abidjan
Quaternary aquifer using DRASTIC method. In: Xu,Y. & Usher, B. (eds.) Groundwater pollution
in Africa, Taylor & Francis, London, 115–124.
JICA 1999. Country profile on environment and water development projects – Senegal. Japan
International Cooperation Agency Annual Report, November 1999.
Jones, H. A. & Hockey, R. D. 1964. The geology of part of southwestern Nigeria. Geological Survey
of Nigeria, Bulletin, 31.
Jourda, J. R. P. 2003. Evaluation de la pollution et de la vulnérabilité des aquifères des grandes
cités urbaines d’Afrique. Project UNEP/UNESCO/UN-HABITAT/ECA. Rapport sur les activités
en Côte d’Ivoire. Rapport à mi-parcours de la 2 ème phase. Décembre 2003.
Jourda, J. R. P. 2004. Qualité des eaux souterraines de la nappe d’Abidjan. Bulletin N4. Juin 2004.
Jourda, J.P., Kouame, K.J., Saley M.B., Kouame, K.F., Kouadio, B.H. & Kouame, K. 2006. Anew
cartographic approach to determine the groundwater vulnerability of the Abidjan aquifer. In:
Xu, Y. & Usher, B. (eds.) Groundwater pollution in Africa, Taylor & Francis, London, 103–114.
Kouadio, L. P., Abdoulaye, S., Jourda, P., Loba, M. & Rambaud,A. 1998. Conséquences de la pollu-
tion urbaine sur la distribution d’eau d’alimentation publique à Abidjan. Cahier de l’Association
Scientifique Européenne pour l’Eau et la Santé, 3, 61–75.
Krothe, J. N., Garcia-Fresca, B. & Sharp, J. M. 2002. Effects of urbanisation on groundwater systems.
In: Proceedings of the XXXII IAH Congress on groundwater and human development, 21–25
October 2002, Mar del Plata, Argentina.
Lerner, D. N. & Barret, M. H. 1996. Urban groundwater issues in the United Kingdom. Hydrogeology
Journal, 4, 80–89.
Longe, E. O., Malomo, S. & Olorunniwo, M. A. 1987. Hydrogeology of Lagos metropolis. Journal
of African Earth Sciences, 6, 163–174.
Lorenzo-Rigney, B. & Sharp, J. M. Jr. 1999. Urban recharge in the Edwards aquifer. Geological
Society of America Conference, 31, A-12.
Matthess, G. Foster, S. S. D. & Skinner, A. C. 1985. Theoretical background, hydrogeology and
practice of groundwater protection zones, IAH International Contributions to Hydrogeology, 6,
Verlag Heinz Heise, Hannover,167–200.
Meyer, P. S. 2001. An explanation of the 1:500 000 hydrogeological map of Cape Town 3317.
Department of Water Affairs & Forestry, SouthAfrica, 59p.
Morris, B. L., Lawrence, A. R., Chilton, P. J., Adams, B., Calow, R. C. & Klinck, B. A. 2003.
Groundwater and its susceptibility to degradation: A global assessment of the problem and options
for management. EarlyWarning and Assessment Report Series, RS. 03-3. UNEP, Nairobi, Kenya.
Mpamba, N. H, Nkhuwa, D. C. W., Nyambe, I. A., Mdala, C. & Wohnlich, S. 2008. Groundwater
mining: A reality for the Lusaka urban aquifer? This volume.
Nkhuwa, D. C.W. 1999. Is groundwater management still an achievable task in the Lusaka aquifer?
Proceedings of the XXIX Conference of IAH, Bratislava, Slovak Republic. 209–213.
Nkhuwa, D. C. W. 2006. Groundwater quality assessments in the John Laing and Misisi areas of
Lusaka. In: Xu, Y. & Usher, B. (eds.) Groundwater pollution in Africa,Taylor & Francis, London,
239–251.
Oga, M. S., Marlin, C., Njitchoua, R., Dever, L. &Filly, A. (this volume)Hydrochemical and isotopic
characteristics of groundwater from coastal sedimentary basin in Abidjan. This volume.
Parsons, R. & Taljard, M. 2000. Assessment of the impact of the Zandvliet Wastewater Treatment
Works on groundwater. Biennial Conference, Sun City, 28 May – 1 June, 2000. Water Institute of
South Africa.
Sharp, J. M. Jr. & Banner, J. L. 2000. The Edwards aquifer: Water for thirsty Texans. In: Schneiderman,
J. S. (ed.)The Earth Around Us: Maintaining a Livable Planet. Freeman, NewYork, 154–165.
Soro, N. 2003. Gestion des eaux pour les villes africaines : évaluation rapide des ressources en eau
souterraine/occupation des sols. UN-HABITAT. Avril 2003 (Rapport final).
Adelana ch014.tex 17/4/2008 12: 14 Page 260
260 Applied groundwater studies inAfrica
Tandia,A. A., Gaye, C. B. & Faye, A. 1998. Origin, process and migration of nitrate compounds in the
aquifers of Dakar region, Senegal. In: Application of isotope techniques to investigate groundwater
pollution, IAEATECDOC-1046, 67–80.
Taylor, R. G., Barret, M. H. & Tindimugaya, C. 2004. Urban areas of Sub-SaharanAfrica: Weathered
crystalline aquifer systems. In: Lerner, D. N. (ed.) Urban groundwater pollution, IAH International
Contributions to Hydrogeology, 24, Balkema,The Netherlands, 155–179.
Theron, J. N., Gresse, P. G., Siegfried, H. P. & Rogers, J. 1992. The geology of the Cape Town area.
Explanation on Sheet 3318, Geological Survey, South Africa.
UNPD 2005. World Population Prospects: The 2004 Revision and World Urbanization Prospects.
Available on the web: http://esa.un.org/unpp.
Usher, B. H., Pretorius, J. A., Dennis, I., Jovanovic, N., Clarke, S., Titus, R. & Xu, Y. 2004.
Identification and prioritisation of groundwater contaminants and sources in SouthAfrica’s urban
catchments. WRC Report, 1326/1/04.
... Terms generally ascribed to the impairment of water include water degradation, pollution, or contamination (Novotny, 2003). Urbanization, population explosion, agrarian, and industrial activities in most of the tropical region, for instance, in Nigeria, create serious pollution threats and simultaneously cause health hazards to the quality of groundwater, particularly in urban and periurban areas (Adelana et al., 2008;Macdonald et al., 2009). In some areas, groundwater contains particular ions and toxic elements in concentrations detrimental to health, while others contain elements or compounds that create different sorts of problems. ...
... The rapidity of urbanization in Nigeria is a result of high population density, rising industrial and agrarian activities, environmental degradation, and unregulated disposal of various forms of wastes that seem to create stern pollution threats with all its related health risks on groundwater quality particularly in urban regions (Adelana et al., 2008;Eni et al., 2011;Ocheri et al., 2014;Owoyemi et al, 2019). This situation has stirred up researchers' attention in various sections of Nigeria's urban regions. ...
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... Groundwater is considered a safe and reliable source of drinking-water in many parts of Africa (Foster et al., 2008). Adelana et al. (2008) identi ed 49 cities that are heavily dependent on groundwater resources in Sub-Saharan Africa (SSA) especially for drinking water needs. Within the urban and peri-urban contexts, this has led to widespread unpreceded development of groundwater resources. ...
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Groundwater is becoming a more accessible and comparatively cheap source of water for drinking, agriculture and industry in Zambia than surface water. However, in Lusaka, the country’s capital city, increased rates of urbanisation have caused large numbers of people who cannot readily obtain water supply services by self-provision to exploit any other available sources of groundwater supply, thereby exerting enormous pressure on the Lusaka aquifer through construction of private boreholes or hand-dug wells. Consequently, contamination in the city aquifer appears to be increasing and waterborne diseases have increased to endemic levels as well. Keywords: health, Lusaka, pollution, urbanisation, vulnerability
Chapter
The city of Lusaka has historically depended on groundwater from the underlying karstic carbonate and schist aquifers. Inadequate hydrogeological data has hitherto hampered determination of the effects of increasing groundwater abstraction on groundwater levels. Although the recharge estimates vary widely from 8% to 35% of the annual rainfall, groundwater resources availability in terms of quantity and quality, as well as annual recharge and recharge mechanisms are still not well understood. On-going research, using a comparative analytical model for groundwater monitoring in the urban and rural areas of Zambia, gives preliminary evidence of groundwater mining and direct contamination of the Lusaka urban aquifers. In the absence of legal instruments and management tools to enhance the acquisition of groundwater data and information, establishing the capacity of the aquifer to cope with the present and future water demands poses the greatest challenge for the Lusaka city aquifers.