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MPhil in Engineering for Sustainable Development

global challenges, engineering solutions

Studying at Cambridge

Joel Westberg

Evaluation of the Potential, Benefits and Risks of Self Supply Water

Joel Westberg

Evaluation of the Potential, Benefits and Risks of Self Supply Water

 

Self Supply is one of the four flagship themes that the Rural Water Supply Network has identified that will help to reduce cost and improve the sustainability of rural water supplies in Sub-Saharan Africa. It is defined as the improvement of community or household water supplies through user investment in supply, construction and upgrading of wells, rainwater harvesting, and household water treatment. It is based on the concept of incremental improvement to water supplies that are easily replicable and affordable to users. This represents a shift in thinking from the dualistic approach of looking at sources as either “improved” or “unimproved”, and sees unimproved sources as potential improved sources through a ladder of progressive potential improvements that can be facilitated by strategic government and NGO support placing the end-user at the centre of the development process.

Governments and NGOs have previously been hesitant to support self-supply due to a number of justifiable concerns; namely perceived poorer water quality, the fear that incremental improvements can become the permanent solution, and lower ability to categorise the results of investment. While these barriers are beginning to be overcome, there is still a knowledge gap with respect to water quality.

Based on a study performed by RIPPLE in Ethiopia, a comparison of different types of wells and the factors that influence quality was performed including two sanitation surveys. Key findings included that there is little difference between microbiological quality in traditional wells in the dry season compared to protected springs in Ethiopia. Results indicate the wet season significantly reduces water quality in traditional wells and household filtration improves the quality of water at point of use. During the dry season, quality was better in wells with improved aprons, as the length of lining increased, and as the seal of the well improved confirming that one major route of contamination is directly above and around the well head. Some surprising results showed that water quality decreased as latrine distances increased, when the area around the well was drier, and if the bucket was stored in the well compared to leaving it on the ground. However, when wet season data is used, these trends were reversed or different groupings became indistinguishable from each other.  The less detailed UNICEF sanitary survey performed during the wet season showed much poorer correlation between well characteristics and water quality on the same 90 wells that were surveyed in the dry season. However, when a larger data set is used from the wet season (n = 346), each factor did have some effect on the quality of water, and the overall scores were significantly associated with a certain level of contamination.

While these surveys may be helpful for determining which factors influence water quality, it appears as though they currently are not capturing the complexity or inherent variability in the testing method that contributes to overall microbiological water quality results. Statistical analysis of individual factors in addition to overall scores helps to identify which factors are more significant, but also highlights this complexity. Therefore, they should not be relied on to predict water quality.

Improving traditional groundwater sources may be a very important component of self-supply, but the fact that there are so many factors influencing quality suggests that protecting a source alone will not be sufficient to consistently achieve good quality water. Source improvement must be promoted alongside household water treatment within an even larger hygiene and sanitation education programme to minimise the investment of the user while maximising the health, reliability and economic benefits, engage and provide the user with a number of options to chose from, and further utilise whatever available sources there are locally. Only through this multi-faceted, multi-barrier approach will the goals of safe water, improved reliability, adequacy, poverty reduction and adaptation to climate change be achieved.