An Exploration into Fault Tree Analysis (FTA) Applied to Rural Drinking Water Systems

Increasing demand for water to meet a variety of needs places stress on shared sources, and gives rise to the requirement for effective techniques and practices in water resource development. Fulfilling the demand for water also requires assessing the potential for contamination of water used for human consumption and ensuring a sufficient quantity. Delivery of clean water at the point of use / consumption involves a number of steps from the source (where water is typically collected in containers), through transportation, storage, and treatment. Any of these steps carries a potential for contamination or failure in terms of final volume of water delivered to the household. It is suggested in this research that probabilistic risk analysis (PRA) methods combined with the application of fault tree analysis (FTA) represents an effective means to characterize these steps and the impact they have on the overall success or failure of the water development system. PRA provides a systematic means of quantifying the impact of the uncertainties in each step, whereas FTA provides a visual representation of those sequences of events that can lead to failure of the system. The field methods used for this research include individual household surveys and the collection of basic water quality data in the region of Buyamba, Uganda. The research question asks whether the data necessary to estimate the probabilities of failure for each step can be collected from the field work methods, allowing for the potential application of FTA in the assessment of quantity and quality failures in local potable water resource systems. Preliminary conclusions include: i) a fault tree can be constructed to represent the routes to failure in the system, ii) local water practitioners appear to view the resulting fault tree as a useful tool in the design of water development projects, and iii) measuring necessary and sufficient data in the field to quantify probabilities for FTA is possible, but will require both substantial application of the field surveys and careful attention to cultural sensitivities.