OR/17/056 Lusaka case study

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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.

Setting

Lusaka is the capital of Zambia with a rapidly-growing population. The 2010 national census reports the population of Lusaka as 1.7 million, with an average annual growth rate between 2000 and 2010 of 4.9% (Abujafood, 2013[1]). The population of the Lusaka Province is c. 2.2 million; an increase of 0.7 million since 2000. Population growth is from both migration from rural areas but also from the Copper Belt. The majority of the population in Lusaka, up to 70%, live in peri-urban settlements, both formal and informal. Low–income, densely populated settlements lie to the north, north-west and south of the central district. These generally lack well-functioning water and electricity supplies, sewerage systems and solid waste collection (Grönwall et al., 2010[2]).

Nkhuwa (2003)[3] reported a high incidence of gastro intestinal diseases, such as diarrhoea, dysentery and cholera between 1997 and 1999. In this period infant mortality in the poorest households was as likely in the most developed province of Lusaka as the poorest area in Zambia (Madise et al., 2003[4]). Grönwall et al. (2010)[2] also reported cholera outbreaks in the city.

Nyambe et al. (2007)[5] state that Zambia is one of the most urbanised countries in southern Africa with 40% of the population living in urban areas. This is concentrated in unplanned settlements or peri-urban areas of Lusaka and the Copperbelt towns of Ndola and Kitwe. Common features of these settlements are overcrowding, poor water supply and sanitation coupled with high rate of unemployment and disease. There are 372 peri-urban areas in Zambia of which only 51% are legalised. Residents are supplied with water through domestic connections, communal taps and water kiosks (Nyambe et al., 2007[5]). Sharma et al. (2005)[6] evaluates the sustainability of handpumps in rural and semirural areas of Zambia.

Hydrogeology

Lusaka is underlain by a thick sequence of Pre-Cambrian Katangan metasedimentary rocks (Figure 8.1). The northern part of the city, where the formal settlements are, is underlain by strongly folded and faulted Ridgeway Schist and Matero Quartzite. Some groundwater is available from carbonate sequences in the schists. Below this are high-yielding karstified limestone/dolomitic marble of the Lusaka Dolomite Formation, which out-crops in the southern part of the city. Yields are highest in the top 30 m or so of the strata, where fissures are well developed. These aquifers provide a significant proportion of the water supply to the city of Lusaka, especially from karstic sections, where boreholes yield up to 35–50 l/s (BGS, 2001[7]).

Groundwater flow is from SE to NW. The water table is relatively shallow, typically 6 to 15 m below ground surface, but can be as shallow as 0.5 m. Water levels are declining in some places, ascribed to over abstraction, which leads to shallow wells drying-up during the dry season, particularly in the schist and quartzite areas. In other areas, abstractions mitigate the annual risk of flooding (Von Münch and Mayumbelo, 2007[8]; De Waele et al., 2004[9]; Mpamba et al., 2008[10]).

Yields from boreholes in the limestones are high, but because of the karst nature of the aquifer, the success rate is less than 50%. Low yields and borehole failures in the schists and quartzites are attributed to poor local drilling practice (Grönwall et al., 2010[2]). Typical borehole depths are around 50–70 m below ground level.

The Lusaka terrain shows a complete lack of surface water drainage due to the karst nature of the aquifer and, as such, rain and wastewater drain rapidly to groundwater with little natural attenuation (Nkhuwa, 2006[11]).

File:OR17056fig8.1.jpg
Figure 8.1    Geological map of the Lusaka area (Source: Nkhuwa (2003))

Water supply

The city derives about 70% of its total water supply, which amounted to some 240 000 m3/day in 2004, from groundwater with the remainder coming from the Kafue river (De Waele et al., 2004[9]). It is estimated that between 80 000 and 150 000 m3 of groundwater are also abstracted daily from the ground by private boreholes and shallow wells (De Waele et al., 2004[9]; Nyambe et al., 2007[5]). In 2010, it was estimated that there might have been 1900 registered private boreholes and at least as many unregistered ones. In addition, there are a large number of shallow hand-dug wells in backyards. Figure 8.2 gives the spread of boreholes across the Lusaka landscape in the late 1990s (Nkhuwa, 2003[3]).

Most residents in high-density settlements lack a connection to the reticulated supply. The only options, when/where available, are communal taps, community based schemes using NGO boreholes, rare public taps, public hand-pumps and water kiosks, where water may be purchased from the water company or from private borehole owners. As such, shallow hand-dug wells are common in these areas of Lusaka, most of which are open and lack any stone or brick lining. These give moderate to good yields since water is drawn in relatively small quantities. Little, if any, of the water from these private sources is treated before use (Grönwall et al., 2010[2]). Industries and commercial farms in and around Lusaka also use groundwater.

UN Habitat (2010)[12] assessed that almost all households in Lusaka, including those in the urban area, have access to safe drinking water (Figure 8.3), but this may be a long distance away and may necessitate spending long hours in queues.

File:OR17056fig8.2.jpg
Figure 8.2    Distribution of the water supply authority and private boreholes in Lusaka in the mid-late 1990s (modified after Nkhuwa (2003)[3]).
File:OR17056fig8.3.jpg
Figure 8.3    Households in the Lusaka urban area with access to: a) safe drinking water; b) sanitary means of excreta disposal (from UN Habitat, 2010[12]).

Sanitation

The lack of a sewerage system means that sanitation provision in the peri-urban and up-coming low-density areas is generally left to the initiative of the residents, the majority of whom use on-site pit latrines and septic tanks, respectively, that they dig within their plot boundaries (von Münch and Mayumbelo, 2007[13]). The pits are covered with soil once they are full. The liquid fraction of the excreta percolates into the ground and ultimately reaches the groundwater. To avoid these pit latrines filling up quickly, the practice has been to dig them quite deeply, 4–6 m, which results in less attenuation of the leachate to groundwater (Nkhuwa, 2003[3]).

File:OR17056fig8.4.jpg
Figure 8.4    Proximity of water supply sources to on-site sanitation facilities in low- and high-density settlements of Lusaka. (Nkhuwa, unpublished (left) & 2006 (right)).

There are some VIP latrines, but many are of rudimentary construction, unlined or are shared. People may also use dried up wells in the dry season (von Münch and Mayumbelo, 2007[13]). Many latrines and septic tanks are typically close to water supply wells (Figure 8.3). The sanitation coverage (ratio of population with access to adequate sanitation) is quite low — only 17% (Bäumle et al., 2010[14]). This poses great risk to the quality of groundwater.

File:OR17056fig8.5.jpg
Figure 8.5    Locations of waste disposal sites and public supply boreholes in Lusaka (Nkhuwa, 2003[3]).

Other sources

Lusaka produces about 1.1 tonnes/day of solid waste, of which only about 10% is collected (De Waele et al., 2004[9]). This is transported away from the city to landfill. The remainder of the solid wastes are often dumped between houses or dumped in uncontrolled sites on the dolomite, perhaps filling old quarries (Cidu et al., 2003[15]). Waste dumped in these features consisted of, among others, old car bodies, oils and various forms of infectious/hazardous clinical wastes (Nkhuwa, 2003[3]) with some medical waste also being disposed of inappropriately in refuse pits (Nkhuwa et al., 2008[16]). UN Habitat (2010)[12] assessed that solid waste disposal is very poor across Lusaka with the potential for the spread of disease.

Groundwater quality

Limited baseline data available suggest possible high fluoride in some parts of Lusaka (BGS, 2001[7]). Bäumle et al. (2010)[14] showed that there are still areas with water quality unaffected by human activity, in which SEC is less than 800 mS/cm and nitrate, chloride and sulphate below 10 mg/L. Groundwater was still considered acceptable for domestic use after treatment in 2004 (De Waele et al., 2004[9]). Under the prevailing pH (median = 7.0, min = 5.8, max = 8.0) in the calcareous geological environment, potentially toxic heavy metals like lead, cadmium or arsenic as well as iron or manganese tend to form hydroxyl- and carbonate complexes which are insoluble and can therefore not be found in the water. Thus, concentrations of these cations are generally well below the WHO limit in groundwater. Nachiyunde et al. (2013)[17] also assessed both nitrate and sodium to be widespread and prominent in high density residential areas. Table 8.1 gives a summary of the inorganic water quality in different parts of Lusaka undertaken by different researchers between 2003 and 2013.

In one large-scale groundwater study in 1978 (von Hoyer et al., 1978[18]) there was bacteriological and chemical pollution in all the water samples tested. The study also revealed that both biological and chemical content of the water varied with season and borehole locality. Exceptionally high values were recorded during the rainy season and in areas that are reliant on pit latrines and septic tanks. Further, chemical and bacteriological investigations conducted in 1996 also revealed considerable and variable levels of pollution in the same areas (Nkhuwa, 1996[19]). Isotopic studies conducted by Nkhuwa and Tembo (1998)[20] indicated that the greatest susceptibility to pollution of the aquifer occurs mainly in the rainy season (November–April) when recharge to the groundwater store occurs. This study also showed that this process is especially exacerbated during periods of continuous and prolonged rainfall.

In the 1990s many boreholes had high concentrations of total and faecal coliforms. All data reported by (Nkhuwa, 2003[3]) were positive and 28% had total coliforms TNTC (Table 8.2). In 2008 and 2010, only one third of sampled boreholes were below the Total Coliform limit of MPN=20 under the ZDWS, whereas elevated concentrations of Escherichia coli occurred much less frequently (Bäumle and Nick, 2011[21]). Nitrate concentrations were found to be very high in many boreholes and often exceeded the Zambian Drinking Water Standards (ZDWS) limit of 44 mg/L. While the large production public supply boreholes of LWSC exhibit nitrate concentrations below the ZDWS, boreholes for the local supply of peri-urban high density settlement areas showed considerably higher values, with some exceeding 100 mg/L. Groundwater in the vicinity of medical waste disposal sites (Nkhuwa et al., 2008[16]) showed variable levels and evidence of pollution dependent on clinic practices (Table 8.2).

Table 8.1    Inorganic water quality in Lusaka.
Supply NO3 (mg/L) Mean (Range) NH4 (mg/L) Cl (mg/L) SEC (µS/cm) Other (µg/L) Reference
Buckley 13 0.08 52 Alkalinity 361 Nkhuwa (2003)[3]
John Laing 39.5 59.7 102 211
Kamanga 10.3 10.3 42.3 564
Woodlands 0.03 0.9 90.1 124
Wells and surface water, Lusaka 16.8
(0–43) 		0.99
(<0.25–>4) 		14.7
(4.2–36) 		570
(200–860) 		Hg <0.4–13 Cidu et al. (2003)[15]; (De Waele and Follesa, 2003[22]; De Waele et al., 2004[9])
Affected areas 123 1450 (Bäumle et al., 2010[14])
Lusaka province 19.1
(0–128) 		3.09
(0.17–6.49) 		19.2
(0.63–73) 		Nachiyunde, K et al. (2013)[17]
Table 8.2    Microbiological water quality in Lusaka.
Supply/Area SEC COD Total Coli
(counts/100mL) 		Faecal Coli
(counts/100mL) 		Reference
Near medical clinics 669 (506–1060) 52 (48–64) 20 (0–58) 14 (0–45) Nkhuwa et al. (2008)
Chawama NA 58 (9–320) 19 (1–TNTC) 21, TNTC Nkhuwa (2003)[3]

Aquifer management

This has involved groundwater monitoring and sampling network, thematic mapping, development of groundwater information system, capacity building and awareness raising (Bäumle et al., 2010[14]; Bäumle and Nick, 2011[21]). An outline is shown in (Figure 8.6).

Kang’omba and Bäumle (2013)[23] make the following recommendations for managing groundwater.

  • They assessed the current level of groundwater abstraction as sustainable but to safeguard supplies by continuing conjunctive use of surface water and to transfer some large abstraction to areas 5–30 km from the city.
  • To improve sanitation, including biogas systems, and dry toilets, focussing first on highly vulnerable areas
  • To protect groundwater by a zoned approach of land-use restrictions and to improves these zones using tracer tests.
  • To make the city council responsible for water and sanitation and to provide resources for this
File:OR17056fig8.6.jpg
Figure 8.6    Simplified flowchart showing the investigation program towards the development of a groundwater management strategy for Lusaka (after BGR, 2013[24]).

References

  1. ↑ ABUJAFOOD. 2013. Top 5 Cities in Nigeria by Population. Nigeria: Lagos, the mega-city of slums. Energypublisher.com. https://www.energypublisher.com/article.asp?id=5307
  2. ↑ 2.0 2.1 2.2 2.3 GRÖNWALL, J T, MULENGA, M, and MCGRANAHAN, G. 2010. Groundwater, self-supply and poor urban dwellers: A review with case studies of Bangalore and Lusaka. (London: IIED.)
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 NKHUWA, D C W. 2003. Human activities and threats of chronic epidemics in a fragile geologic environment. Physics and Chemistry of the Earth, Vol. 28, 1139–1145.
  4. ↑ MADISE, N J, BANDA, E M, and BENAYA, K W. 2003. Infant mortality in Zambia: Socioeconomic and demographic correlates. Biodemography and Social Biology, Vol. 50, 148–166.
  5. ↑ 5.0 5.1 5.2 NYAMBE, I A, KAWAMYA, V M, LYAMBA, K, and YONDELA, G. 2007. Do existing national policies, strategies and guidelines take into account the characteristics of peri-urban areas in Zambia. UNESCO — Institute for Water Education.
  6. ↑ SHARMA, S K, NUMWA, N G, and AMY, G. 2005. Evaluation of handpump water supply in selected rural and semi-urban areas of Zambia. 31st WEDC International Conference: Maximizing the benefits from water and environmental sanitation. Kampala, Uganda.
  7. ↑ 7.0 7.1 BRITISH GEOLOGICAL SURVEY. 2001. Groundwater quality: Zambia. https://www.wateraid.org/~/media/Publications/groundwater-quality-information-zambia.pdf
  8. ↑ VON MÜNCH, E, and MAYUMBELO, K. 2007. Methodology to compare costs of sanitation options for low-income peri-urban areas in Lusaka, Zambia. Water SA, Vol. 33, 593–602.
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 DE WAELE, J, NYAMBE, I A, DI GREGORIO, A, DI GREGORIO, F, SIMASIKU, S, FOLLESA, R, and NKEMBA, S. 2004. Urban waste landfill planning and karstic groundwater resources in developing countries: the example of Lusaka (Zambia). Journal of African Earth Sciences, Vol. 39, 501–508.
  10. ↑ MPAMBA, N H, HUSSEN, A, KANGOMBA, S, NKHUWA, D C W, NYAMBE, I A, MDALA, C, WOHNLICH, S, and SHIBASAKI, N. 2008. Evidence and implications of groundwater mining in the Lusaka urban aquifers. Physics and Chemistry of the Earth, Vol. 33, 648–654.
  11. ↑ NKHUWA, D C W. 2006. Groundwater quality assessment in the John Laing and Misisi areas of Lusaka. 239–252 in Groundwater pollution in Africa. XU, Y, and USHER, B (editors). (Leiden: Taylor & Francis/Balkema.)
  12. ↑ 12.0 12.1 12.2 UN HABITAT. 2010. Intra-Cities Differentials Lusaka, Zambia.
  13. ↑ 13.0 13.1 VON MÜNCH, E, and MAYUMBELO, K. 2007. Methodology to compare costs of sanitation options for low-income peri-urban areas in Lusaka, Zambia. Water SA, Vol. 33, 593–602.
  14. ↑ 14.0 14.1 14.2 14.3 BÄUMLE, R, HAHNE, K, MUSETEKA, L, and NICK, A. 2010. Developing of an aquifer management strategy for the rapidly expanding City of Lusaka, Zambia. Groundwater Quality Sustainability, Krakow, 12–17 September 2010, University of Silesia Press. Cite error: Invalid <ref> tag; name "Bäumle 2010" defined multiple times with different content
  15. ↑ 15.0 15.1 CIDU, R, DE WAELE, J, DI GREGARIO, F, and FOLLESA, R. 2003. Geochemistry of groundwater in an intensely urbanised karst area (Lusaka, Zambia) GeoActa, Vol. 2, 35–42.
  16. ↑ 16.0 16.1 NKHUWA, D C W, KAFULA, T, and AHMED, A H. 2008. A preliminary inventory of hazardous medical waste disposal systems and their influence on groundwater quality in Lusaka. Medical Journal of Zambia, Vol. 35, 129–138.
  17. ↑ 17.0 17.1 NACHIYUNDE, K, IKEDA, H, TANAKA, K, and KOZAKI, D. 2013. Evaluation of portable water in five provinces of Zambia using a water pollution index. African Journal of Environmental Science and Technology, Vol. 7, 14–29.
  18. ↑ VON HOYER, M, KÖHLER, G, and SCHMIDT, G. 1978. Groundwater and management studies for Lusaka. Water Supply. Part 1. BGR (Hannover).
  19. ↑ NKHUWA, D C W. 1996. Hydrogeological and engineering geological problems of urban development over karstified marble in Lusaka. RWTH Aachen University.
  20. ↑ NKHUWA, D C W, and TEMBO, F. 1998. Groundwater recharge and susceptibility to pollution of the Lusaka aquifer. Proceedings of the International Symposium on Isotope Techniques in the Study of Past and Current Environmental Changes in the Hydrosphere and the Atmosphere. Vienna, Austria, IAEA, 837–839.
  21. ↑ 21.0 21.1 BÄUMLE, R, and NICK, A. 2011. Development of groundwater management tools, guidelines and strategies for the Southern Province and the City of Lusaka, Zambia. BGR (Lusaka).
  22. ↑ DE WAELE, J, and FOLLESA, R. 2003. Human impact on karst, the example of Lusaka (Zambia). International Journal of Speleology, Vol. 32, 71–83.
  23. ↑ KANG'OMBA, S, and BÄUMLE, R. 2013. Development of a groundwater information and management program for the Lusaka groundwater systems. DWA-MMEW, BMZ & BGR Final Report (Lusaka).
  24. ↑ BGR. 2013. TC Zambia: Groundwater Information System and Management Programme for Lusaka. Hannover: Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) [Federal Institute for Geosciences and Natural Resources]. https://www.bgr.bund.de/EN/Themen/Wasser/Projekte/laufend/TZ/Zambia/zambia_lusaka_prov_fb_en.html
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