OR/17/056 Groundwater in urban Sub-Saharan Africa

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Lapworth, D J, Stuart, M E, Pedley, S, Nkhuwa, D C W, and Tijani, M N. 2017. A review of urban groundwater use and water quality challenges in Sub-Saharan Africa. British Geological Survey Internal Report, OR/17/056.

The role of groundwater

Groundwater is the critical underlying resource for human survival and economic development in extensive drought-prone areas of south-eastern, eastern and western Africa, especially where the average rainfall is less than 1000 mm/a (Foster et al., 2006[1]). Rainfall tends to be variable year to year, which creates difficulties for managing the quantity and quality of groundwater resources, and this variability is likely to increase with the growing impact of climate change (Carter and Parker, 2009[2]). There are also a number of trans-boundary aquifers which require strategic management (Ashton and Turton, 2009[3]). The proximity of groundwater sources, and the related reduced infrastructure costs, makes urban groundwater an ideal resource to target for development in SSA (Foster et al., 1998[4]; Taylor and Barrett, 1999[5]); however, the susceptibility of groundwater to contamination in urban settings has to date received little attention compared to other regions globally.

In large parts of rural SSA the functioning of infrastructure facilities is dependent on groundwater supplies. Groundwater is used for urban water supply, industrial and tourist development and as a critical resource for the development of mining and other industrial activity (Foster et al., 2006[1]). Demand for groundwater is already high and will continue to grow for the foreseeable future.

Africa’s population is increasing rapidly, often exceeding 5% growth per annum. With a four-fold increase in urban population projected over the next 50 years the provision of safe water and food will be a significant challenge (Carter and Parker, 2009[2]). In Africa about one third of the total population lack adequate access to improved water supplies and approximately 70% are not using improved sanitation. The widespread lack of access to these basic services are thought to be the root cause of many diseases that affect Africa (Braune and Xu, 2010[6]).

In a substantial number of large towns groundwater is vital to the continuity of water supply and plays a key role in droughts and other emergencies. Yet in only a few cases has the use of groundwater evolved as part of planned water-supply development; more commonly it has occurred in response to water shortage or service deficiency and often through private initiative (Foster et al., 2006[1]). Groundwater has a vital role in serving the large informal areas that do not have ready access to piped water supplies but this usage is often not formally recorded (Braune and Xu, 2010[6]). In addition, wastewater infiltration in urban areas is a growing concern for groundwater quality (Foster et al., 2006[1]).

While regional scale assessments of groundwater resources have been recently quantified (MacDonald et al., 2012[7]), hydrogeological evidence at the appropriate resolution for managing groundwater resources in many African urban centres is non-existent. There is a lack of appropriate approaches and investment for planning, financing and sustainably using this important resource (Braune and Xu, 2010[6]). Additionally there has been concern over:

  • The decline of national institutions responsible for groundwater development, resource administration, groundwater protection and database management, as well as loss of professional personnel since the 1980s (Foster et al., 2006[1]).
  • Legislation not catering for community-based arrangements but focussing on centralised government permits at the river basin scale.

Urban and peri-urban development

There continues to be a lively discourse regarding population dynamics, urbanisation and urban economies in Africa. One perspective is that rapid urban growth, some fuelled by in-migration from rural areas, has economic benefits (UN, 2005[8]). While the rates of urbanisation may still be overestimated (Potts, 2009[9]), there is a clear consensus that there is undoubtedly significant growth in the urban population in SSA, whether this is through natural growth, in-migration or simply the reclassification of settlements based on somewhat arbitrary thresholds.

Simon (2008)[10] defines the peri-urban zone or rural-urban fringe, which he distinguishes from suburbs, using urban influence, changing land use, access to infrastructure, services and markets, and exposure to urban processes and pollution. He concludes that it is best visualised as a continuum which varies in extent both spatially and temporally. Mpofu (2013)[11] set out the main environmental challenges for urbanisation in Sub-Saharan Africa as crowded living conditions, poor disposal of wastes, inadequate basic infrastructure, pollution of water and the decline of urban green areas. The causes are natural urban population growth, rural to urban migration, poor development control, weak institutions and inadequate financial resources.

Evolution of groundwater development during expansion of urban centres

Foster et al. (1998)[4] summarised the evolution of groundwater in urban settlements and outlines the interdependence of groundwater and urbanisation. A four stage model was proposed:

1) Early settlement:

  • Water supply obtained from shallow urban wells and boreholes
  • Wastewater discharged to ground
  • Pluvial drainage to groundwater or water courses

2) Town-city development:

  • Water table lowered beneath city and wells deepened
  • Wastewater discharged to ground
  • Shallow groundwater in town/city becomes polluted
  • Expansion of pluvial drainage to groundwater/water courses

3) City starts to expand:

  • Local aquifer beneath city is largely abandoned due to contamination
  • Water table rebound occurs in city due to combination of high urban recharge and low pumping rates
  • Explore conjunctive use with sources outside of urban centre
  • Significant water table decline in per-urban area due to development of well fields on edge of city
  • Continued contamination of urban groundwater due to urban recharge

4) Further expansion of city:

  • Well-fields unable to cope with increased demand of city
  • Rise in costs associated with conjunctive use of water from peri-urban and distant sources
  • Steady water table rise in city nucleus leads to problems of flooding and waste water disposal
  • Reduced scope for pluvial drainage to groundwater

This generalises the situation regarding the development of urban groundwater use and degradation. In reality there may be significant differences in the progression of urban groundwater development across SSA due to fundamental hydrogeological and geographical differences, as well as contrasting national and regional approaches to planning and investment in the water sector. Groundwater use and development will also depend on socio-economic factors; for example, the least prosperous areas in urban centres often continue to use unimproved shallow groundwater sources for a number of domestic purposes during phase 3–4, not least because of unreliable and unaffordable supplies, but also because these areas are often located where there are shallow groundwater tables and are prone to flooding e.g. Lusaka. The issue of how previously discrete urban centres merge over time to produce very large and essentially continuous sprawling urban areas (e.g. Lagos and Ibadan in Nigeria), and the competition between urban and peri-urban groundwater for irrigation and agricultural activities are two common issues that are not included.

Urban expansion

Many African economies have undergone a period of structural adjustment to their economic programmes with the overall aims of reducing state-based interventions and balancing the books (Briggs and Mwamfupe, 2000[12]). This has resulted, amongst others things, in the privatisation of previously state-owned agencies and liberalisation of planning regulations, potentially allowing investment and expansion of the peri-urban zones of cities. Briggs and Mwamfupe (1999[13], 2000[12]) describe the history of urban expansion of Dar-es-Salaam, Tanzania. During the economic crisis of the 1980s, many residents bought land and moved to the edge of the urban area in order to produce their own food. These settlements tended to be along arterial roads to allow some household members to continue to work in the city. The original landowners were displaced and moved further out to cheaper land to continue farming. As the economic situation improved the peri-urban zone was developed for permanent housing and for the expansion of commercial agriculture supplying the city with milk, vegetables and fruit. The deregulation of public transport allowed a system of minibuses and similar to service the interstitial areas. Together with increased private vehicle ownership this has allowed dense settlement at locations away from the arterial roads. More recently a shortage of capital has slowed this process down and a lack of business confidence has restricted the development of large factories or other enterprises. Low income groups have been increasingly excluded from peri-urban land as land has been commoditised and wealthier urban groups have benefitted.

Yankson and Gough (1999)[14] made a study of the urbanisation of Accra, Ghana. This fishing village grew rapidly after becoming the seat of British administration in the late 1800s. The stagnation of the economy in the 1970s and 80s resulted in a breakdown of service provision and the deterioration of existing infrastructure. Since then new residential areas have appeared very rapidly with a fragmented urban structure and lack of development controls. There was a shortage of land in the ‘fringe zone’ for farming and degradation of remaining agricultural land due to increased pressures from urban development. The peri-urban environment has changed with far fewer trees as land was converted first to agricultural use and then to residential. There is pressure on water courses and erosion has increased. Many areas did not have a reliable piped water supply and inhabitants had to use poor quality surface water supplemented by treated water from vendors. None of the houses in the peri-urban area had mains sewerage and many areas used improved pit latrines, with others using pan latrines or what the authors term the ‘free-range’ mode. There was no system for solid waste collection, with many people using empty fields or burning it where possible.

Investment in African cities is often externally driven and may not reflect local conditions or benefit local communities. It can also lead to very polarised socio-economic conditions (Mbiba and Huchzermeyer, 2002[15]). In Mombasa investment has been made in tourist facilities at points on the urban periphery, whilst at the same time the urban area deteriorates (Mbiba and Huchzermeyer, 2002[15]). The remainder of the peri-urban area comprises informal settlements where 30% of the population live below the poverty line. In Zambia the informal peri-urban settlements at main city entrance points are said to be an embarrassment to the authorities, who have made efforts to evict or relocate the residents (Mbiba and Huchzermeyer, 2002[15]). In Lusaka half the population live in illegal or informal settlements. Urban peripheries attract some migrants who do not become town dwellers but inhabit or create peripheral villages for subsistence farming (Swindell, 1988[16]). Frumkin (2002)[17] described the impact of urban sprawl on water resources in developed countries as increased run off and less recharge, leading to water shortages in one third of US communities. Water quality can be affected in many ways. In developed countries there is better control of point sources such as factories and sewage treatment works but non-point sources remain an issue. These include oil, grease and toxic chemicals from roads and car parks, sediment from improperly managed construction sites and erosion. Suburban development was associated with polyaromatic hydrocarbons, heavy metals, such as zinc and organic waste.

A clear and consistent picture emerges for the peri-urban areas of Kumasi, Ghana (Simon et al., 2004[18]). Common factors are:

  • Increased population size due to in migration in search of building land
  • Declining area of agricultural land and land under cultivation
  • Reduced farm size due to population growth
  • Decreased soil fertility close to villages with shortened fallow periods and reduced crop yield
  • Increases in facilities and infrastructure — boreholes and dug wells, access roads, schools, pit latrines with some ventilated improved pit latrines (VIP), electricity and piped water for those able to pay
  • Increased mining of sand within villages
  • Sale of land for housing and commercial development

Urban food security and peri-urban agriculture

As the city expands, the greater proximity and access to the enlarged urban market provides new opportunities to increase peri-urban agriculture and to specialise in higher-value horticultural crops, with both increased risks and returns (Simon, 2008[10]). Urban agriculture occurs behind houses, on roofs, along roadsides, railway lines and under power lines, in the middle of roundabouts and in parks (Cofie et al., 2003[19]). In West Africa, Swindell (1988)[16] records intensely cultivated peripheral zones around capital cities which have developed since the 1930s and extend outwards for some 10 km, e.g. around Brazzaville, Congo; Libreville, Gabon; Bangui, Central African Republic; and Bouaké, Ivory Coast. In the Kinshasa periphery there was considerable pressure on land for speculative building and farming and this has led to a zone of intensive farming stretching into the lower parts of the DR Congo. In cities across West Africa such as Dakar, Bamako, Accra, and Ibadan, urban agriculture provides a significant source of income, supplementing other economic activities (Cofie et al., 2005[20]; Cofie et al., 2003[19]).

In East Africa e.g. in Kumasi and Dar-es-Salaam, home gardening or urban agriculture is very common. In both cases urban growing of staple crops, is largely carried out by women and children to reduce household expenses. Open space production generally supplies cities with fresh leafy vegetables and fruit. Farming in larger spaces provides crops such as maize or sorghum and export crops such as flowers. In convenient locations, e.g. near airports, there may be specialist crops such as pineapples. In Dar-es-Salaam, urban agriculture forms 60% of the informal sector and is the second largest urban employer. In Nairobi and Lusaka farming households produce 20–30% of their food requirements, whereas in poorer Harare and Kampala up to 60% is produced. The next stage in expansion is the loss of cultivatable land to a combination of land sale and degradation, and a reduction in food self-sufficiency and surplus for sale (Simon, 2008[10]).

Broad groups of contaminants and threats to groundwater resources

Urban groundwater resources are at risk of pollution by a large number of different broad groups of contaminants including microbiological pathogens, heavy metals (e.g. lead cadmium, and zinc), macronutrients (nitrogen, carbon, potassium and phosphorus), pesticides and herbicides, and a diverse array of other organic contaminants. High concentrations of naturally occurring contaminants such as fluoride, arsenic and uranium are also of concern, and although these are largely controlled by natural processes, anthropogenic influences can affect the hydrogeological regime and hydrogeochemical environment and hence their mobility and transport in the groundwater system. From a health risk standpoint microbiological pathogens and toxic metals are of particular concern and have been the focus of the majority of published studies to date.

Often excessive and inappropriate amounts of fertilisers and pesticides are used for peri-urban agriculture, contaminating crops, soil and water and causing health problems for farmers (Simon, 2008[10]). Due to shortages of land, water and fertiliser, waste by-products and contaminated water are often used for agriculture in peri-urban areas (Binns et al., 2003[21]). In Kano, Nigeria, water treatment and even water supply are non-existent and poor people cannot afford sanitation. Industrial effluents, particularly tannery wastes containing chromium (Cr) and cadmium (Cd), are a threat to local irrigation water as these are routinely discharged to open drains or water courses without treatment. Where factory or sewage waste are applied directly to land these can also carry viruses and high levels of faecal coliforms. There were also high levels of Pb in unpaved road dust and in dust deposition.

Access to water

The provision of water in densely populated peri-urban settlements is complex, involving a mixture of piped water supplies, self-provision and deliveries by small independent water providers (Sorensen et al., 2015a[22]; Matsinhe et al. 2008[23]). Where consumers make their own provision, the distance to a supply and number of users per facility have an impact on the time spent collecting water and therefore the amount of water collected and used (Table 2.1) (Hofmann, 2005[24]). Poorer households often have fewer facilities for storing water in the home (Mweemba et al., 2011[25]) and so will use less water, or spend more time collecting water (towards the left of Table 2.1). At the low end of the scale, adequate volumes for consumption and hygiene cannot be assured. However, as access increases, consumption increases and the volumes of water available for hygiene increases with the result that health concerns may decrease. But the task of collecting water is not evenly distributed across the community.

Studies have shown that over 70% of all trips to collect water are made by women and girls over the age of 15 (Trick et al., 2005[26]) with consequent effects on their education and their health.

Hofmann (2005)[24] has assessed the causes and consequences of lack of access to water supply and sanitation. The author concludes that these problems are particularly important in peri-urban areas. Lack of access can be due to:

  • The legal system — many policies and regulations do not take account of informal settlements, e.g. on tenure issues, and constitute an obstacle to improved access
  • An unfair allocation of resources which do not take account of gender roles, age, ethnicity and disadvantage.

Access to finance can also be a significant barrier to the improved water and sanitation and particularly effects the poorer parts of society (Evans and Trémolet 2010). Evans (2007) outlines some key reasons why poorer parts of urban society are excluded from water and sanitation provision:

  • The distance from trunk infrastructure — resulting high unit cost of service provision
  • The high cost of self-provision due to scale limitations
  • Legal barriers, e.g. land tenure
  • Their location in areas which are more technically challenging — e.g. on steep slopes or have a tendency to flood
  • They are priced out of formal services due to high connection fees (and corruption)
  • They do not have the necessary influence to obtain an official connection through often bureaucratic processes
File:OR17056tab2.1.jpg
Table 2.1    Relation between distance to services, collection time and amount of water used (after Hofmann, 2005[24]).

Musingi et al. (1999)[27] showed how the surface water supply for Mombasa has failed to meet the demand due to urban growth. Groundwater quality is compromised by saline intrusion, pit latrines, and septic tanks. In Old Naledi, Gabarone, Botswana, after rezoning of land for residential use, 93% of the population depended on communal standpipes with the remainder having private connections (Gwebu, 2003[28]). Over ninety percent of the population used pit latrines which filled rapidly, frequently overflowed during the wet season, and continually seeped into groundwater affected nearby water resources.

In Dar-es-Salaam, many peri-urban inhabitants could be described as water poor as they lack access to sufficient water of good quality and adequate sanitation (Allen et al. 2006b[29], see Table 2.2). Customary systems facilitate access to unplanned and high-density low-income housing where groundwater sources are heavily contaminated. As a result, residents are forced to spend a significant part of their income buying water from kiosks, small scale water providers, or other sources. Often, informally supplied water failed to meet minimum standards of quality with impacts on consumer’s health. Water is also required for income generating activities such as food vending, poultry and cattle keeping, concrete block making and textile production and lack of water poses a serious risk to livelihoods, and maintains people in poverty (Wright et al., 2013[30]).

Matsinhe et al. (2008)[23] describe a similar picture for Maputo, Mozambique. Here water delivery to large parts of the peri-urban area depends on informal service provision. Household waters sellers and small independent providers cater for over 20% of unconnected households, with the remainder from private wells and neighbour to neighbour water resale. Jiménez et al. (2012)[31] assessed the role of sustainable urban water distribution and measured the efficiency of a development project in Wukro Town, Ethiopia as a case study. This used the distance to a service connection as a benchmark. The relationship between stakeholders is critical to effective contribution to sustainability.

Links between culture, gender and sanitation in urban SSA

Improved WASH in urban SSA has obvious and well documented sanitary benefits as well as more subtle and poorly documented non-sanitary impacts and benefits (McMichael, 2000[32]). Non-sanitary impacts are briefly reviewed by Pearson and McPhedran (2008)[33], these include enhanced security, education and the dignity of disabled people, this is particularly important for women and girls as well as poor communities (Mweemba et al., 2011[25]). Pearson and McPhedran (2008)[33] note that this is an area of research that has received little attention, and there have been few studies in SSA. New cultural norms take a long time to be adopted, and the WASH sector is by no means immune from this (Paterson et al., 2007[34]). Many projects have found that the up-take and use of improved sanitation and drinking water facilities have been slowed or inhibited by a number of factors, the fact that changes in cultural norms work on the generational time scale while projects often work on the sub-decadal timescale remains a huge challenge. While the adoption of new norms is generally thought to be more rapid in urban settings, understanding these issues and how to enhance early adoption of new cultural norms where possible is critical to the future success of improved access to water and sanitation in SSA.

Table 2.2    Peri-urban water supply in Dar-es-Salaam (after Allen et al., 2006b[29]).
Provider Policy driven practice Needs-driven practice
Public sector Piped network and public standpipes
Wells and boreholes
Provision by tanker 		Water kiosks
Private sector Buying from licensed tankers
Buying packaged water (cans, bottles and sachets) 		Buying from informal tankers
Private vendors drawing from own well or piped connection and sold through pushcarts and bicycle vendors
Community Rainwater harvesting
Water theft
Clandestine connections
Private wells and boreholes
Piped network and taps run with NGO support
Borehole and kiosks run by the community

References

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  30. ↑ WRIGHT, J A, CRONIN, A, OKOTTO-OKOTTO, J, YANG, H, PEDLEY, S, and GUNDRY, S W. 2013. A spatial analysis of pit latrine density and groundwater source contamination. Environmental Monitoring and Assessment, Vol. 185, 4261–4272.
  31. ↑ JIMÉNEZ, R, MAGRINYÀ, F, and ALMANDOZ, J. 2012. The role of urban water distribution networks in the process of sustainable urbanisation in developing countries. Case study: Wuckro Supply. Wukro Town (Ethiopia).
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