Abstract
Sub-Saharan Africa is experiencing rapid urbanisation and many urban residents use groundwater where piped supplies are intermittent or unavailable. This study aimed to investigate long-term changes in groundwater contamination hazards and hand-dug well water quality in two informal settlements in Kisumu city, Kenya. Buildings, pit latrines, and wells were mapped in 1999 and 2013–2014. Sanitary risk inspection and water quality testing were conducted at 51 hand-dug wells in 2002 to 2004 and 2014. Pit latrine density increased between 1999 and 2014, whilst sanitary risk scores for wells increased between 2002 to 2004 and 2014 (n = 37, Z = −1.98, p = 0.048). Nitrate levels dropped from 2004 to 2014 (n = 14, Z = −3.296, p = 0.001), but multivariate analysis suggested high rainfall in 2004 could account for this. Thermotolerant coliform counts dropped between 2004 and 2014, with this reduction significant in one settlement. Hand-dug wells had thus remained an important source of domestic water between 1999 and 2014, but contamination risks increased over this period. Water quality trends were complex, but nitrate levels were related to both sanitary risks and rainfall. Given widespread groundwater use by the urban poor in sub-Saharan Africa, the study protocol could be further refined to monitor contamination in hand-dug wells in similar settings.
Highlights
Urban Africa is expanding rapidly, with its population estimated to grow from around 400 million in 2010 to 1.2 billion by 2050 [1]
As unplanned urban development takes place and population density increases, pit latrines, open defecation by both humans and livestock, uncollected waste and other contamination hazards may potentially develop close to groundwater sources that were originally constructed on sites some distance from such hazards
Long-term groundwater quality monitoring efforts are generally focused on deep aquifers, but from a public health perspective, in sub-Saharan Africa, households are frequently exposed to potentially contaminated water from shallow aquifers
Summary
Urban Africa is expanding rapidly, with its population estimated to grow from around 400 million in 2010 to 1.2 billion by 2050 [1]. Over a quarter of the world’s 100 fastest-growing cities are in Africa and this rapid growth raises concerns over water security. In many cities in Sub-Saharan Africa, shallow wells are a widespread form of self-supply to obtain domestic water, and their use in many expanding urban centres has been documented [3]. They are relatively cheap to build and maintain where conditions are suitable [4], they are often at risk of contamination due to a number of factors, including inflow from surface runoff, contamination as water is abstracted by users, and/or contaminant transport through the unsaturated and saturated zones. Well water contamination in these environments can be associated with inadequate well lining and protection of the wellhead, by-pass pathways such as contaminated buckets and ropes, and by ingress of faecal matter into the underlying aquifer from surrounding hazards such as pit latrines [5]
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