Abstract
Groundwater provides a vital source of drinking water for rural communities in many parts of Africa, particularly in the dry season when there are few safe alternative sources. This paper summarises results from a study (n = 428) assessing dry season water quality, both microbiological and inorganic chemistry, in handpump equipped boreholes (HPBs) across the Ethiopia Highlands (n = 142), Malawi (n = 162) and Uganda (n = 124) using a stratified, randomised sampling design. This study seeks to examine general water quality by randomly sampling rural groundwater supplies across larger areas with different geology and climate. The majority, 72%, of HPBs surveyed provide good quality dry season drinking water as defined by WHO drinking water quality criteria. Within this overall picture, the most notable constraints were from thermotolerant coliforms (TTCs), which exceeded the WHO drinking water guideline of zero colony forming units (cfu/100 ml) in 21% of sites (range 0–626 cfu/100 ml). TTC contamination was found to have a significant and positive correlation with annual average rainfall (ρ = 0.2, p = 0.00003). Across all three countries, WHO health based chemical drinking water quality values were exceeded at 9% of sites and were found for manganese (4%), fluoride (2.6%) and nitrate (2.5%); arsenic concentrations were below the guideline value of 10 μg l−1 (range < 0.5–7 μg l−1). The high percentage of Mn exceedances (14% ± 5.2% >400 μg l−1) found in drinking water sources in Uganda challenges the decision by WHO not to formalise a health-based guideline for Mn. While the overall level of microbiological contamination from HPBs is low, results from this study strongly suggest that at a national and regional level, microbiological contamination rather than chemical contamination will provide a greater barrier to achieving targets set for improved drinking water quality under the UN-SDG 6. Efforts should be made to ensure that boreholes are properly sited and constructed effectively to reduce pathogen contamination.
Highlights
Groundwater is the major source of drinking water in Africa (Foster et al 2008, Pavelic et al 2012, Gaye and Tindimugaya 2019) and use of groundwater for drinking water is increasing due to population and economic growth (Vörösmarty et al 2005, United Nations Department of Economic and Social Affairs Population Division 2019) and the search for climate resilient water supplies (Howard et al 2016)
This study provides an assessment of the baseline drinking water quality from rural handpump equipped boreholes (HPBs) in SubSaharan Africa across a range of different climates and aquifer geology
The results from this study across three countries in Africa show that the majority of drinking water from rural HPBs is found to be of good quality, based on health-based criteria, and certainly better quality than most alternative sources available in rural Africa which confirms earlier smaller scale assessments (Parker et al 2010, Pritchard et al 2016, Macdonald et al 2019)
Summary
Africa wide meta-analyses of groundwater quality have been undertaken for selected water quality parameters, including nitrate (Ouedraogo and Vanclooster 2016), fluoride (Kut et al 2016), arsenic (Ahoule et al 2015) and faecal contamination (Bain et al 2014). These meta-studies have highlighted that the majority of published studies on groundwater quality in Africa have (i) limited geographical and geological scope, (ii) studies rarely consider paired observations of microbiological and chemical water quality, and (iii) results are often reported from a mixture of different groundwater source types (e.g. Smedley 1996, Reimann et al 2003, Parker et al 2010, Sorensen et al 2015b, Bretzler et al 2017)
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