Costing improved water supply systems for developing countries

The aim of this paper is to present a practical manual prepared for the World Health Organization (WHO) on how to identify, collect, estimate and compare costs of the available technical options to provide access to safe drinking water in low-income communities. In order to cost - from a social point of view - an improved water supply technology that is likely to secure access to safe drinking water (as defined by the WHO-Unicef joint monitoring programme for water supply and sanitation), an analytical approach is used that disaggregates the technology process according to its essential components, singled out by an engineering description. Questionnaires were developed to identify the main resources invested in a water supply project and to collect, at different disaggregation levels, four types of costs: investment, operation, maintenance and other relevant costs (e. g. administration). Comparability of these different cost elements is achieved by discounting expenditures at different times to the same reference time. Full and unit cost indicators that allow a least-cost analysis can then be derived from this cost picture. To successfully apply the method to actual projects, a spreadsheet was developed using Microsoft Excel to enable user-friendly implementation of all the costing tasks.