Development of cost functions for water supply and sanitation technologies: case study of Bahir Dar and Arba Minch, Ethiopia

Sustainable and improved water supply and sanitation service provision for communities who are lacking it is the forefront issue of the Millennium Development Goals (MDGs). To assist the achievement of the MDGs, it is essential to overcome the traditional approach to planning water supply and sanitation (WS&S) systems. This study developed user and/or service provider cost functions for available WS&S technologies in the vicinity of Bahir Dar and Arba Minch townships. The cost functions help to estimate the life cycle cost of WS&S systems. Eight water supply and eleven sanitation technologies' design documents and cost data were collected and analysed. Results revealed that the maximum daily water demand and person equivalent were the responsive variables for the initial investment and/or recurrent costs of almost all WS&S technologies, respectively. In addition, disinfectant types, pump head, pipe length and diameter, tower height, well depth, conveyance distance and composting volume were identified as important parameters for the corresponding WS&S technologies. However, the cost of shallow well equipped with hand pump was influenced merely by the well depth. The obtained cost functions contribute to overcoming the common practice of WS&S systems comparison in the study area, which largely focus on their initial investment costs.