Sand dams are a promising water supply technology in semi-arid regions but there has been little study of their water quality. This project aims to address this gap.

At a glance

There are estimated to be 748 million people in the world who do not have access to improved sources of drinking water and 43% of these live in Sub-Saharan Africa. There are lots of technologies that can bring clean water close to people's homes, including sand dams. Sand dams are impermeable concrete structures constructed across seasonal rivers in order to trap both water and sediment (sand) behind them during rain storms.

To date there have been no studies on the quality of water removed from sand dams. We are testing the hypothesis that water in a sand dam is not only protected from contamination, but its quality is improved as it passes through the sand.

This hypothesis will be tested through a combined programme of field measurements, laboratory experiments and computer modelling. If sand dam water quality can be demonstrated to be of acceptable microbiological quality then it can be drunk safely and it is an attractive water supply option for communities and relief and development agencies serving them.

The major impact of this project will be to inform development practice by improving the scientific understanding of sand dams so as to provide donors with the confidence to invest in this low cost technology and thereby improve welfare.

Progress update

The field measurements will be supported by Excellent Development, a UK based charity who have built 325 sand dams in Kenya since 1985. We will randomly select three of their sand dams and install piezometers after the seasonal rain storms. A piezometer is a tube with holes in it such that the water level in the tube reflects the water level in the trapped sand. Samples for water quality testing will be collected from these tubes weekly. A range of water quality parameters will be measured including coliforms, which are the bacteria that cause diarrhoea, and turbidity.

The next stage will be to do lab experiments that replicate conditions within sand dams from the end of the flood events. The final stage will be to create computer models of the sand dam system using the results of the lab and field work. These can be used to understand the effects of factors like grain size, sand dam size and input water quality so that recommendations on sand dam design can be made.

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