How much does it usually cost to provide clean drinking water for one person for a day/week?
To be able to calculate the real cost of providing a drinking water (or sanitation) service, you would need to know the life-cycle costs, i.e. what it costs to sustain a service over a longer period of time.
IRC's WASHCost project and the WASHCost calculator provide tools to calculate life-cycle costs. Based on research in India, Burkina Faso and Ghana, WASHCost has calculated a threshold of funds needed to be allocated per person per year as a necessary condition for sustainability. For a borehole and handpump water system, for example, the capital costs range from US$ 20-61 (2011 prices) per person. On top of that you need reserve US$ 3-6 per person per year to fund recurrent costs. These recurrent costs cover expenditure for operational and minor maintenance, capital maintenance and direct support. Similar figures are available for different types of piped schemes - see http://www.washcost.info/page/2584.
For more detailed analysis you can try out the WASHCost Calculator Beta - http://www.washcost.org/
Visit the WASHCost website for more background documents on life-cycle costs and service delivery ladders: http://www.washcost.info/
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