Sustainable and equitable access to safe water and adequate sanitation are widely acknowledged as important development goals. Mechanisms to achieve these goals are broad and varied in terms of the types of services (water supply, drinking water quality, sanitation, sewerage, and hygiene); the setting (urban, peri-urban, rural); and the typology of delivery (public or private interventions, decentralized delivery, expansion or rehabilitation). In addition, there is a wide spectrum of possible socio-cultural, economic, environmental, political and legal conditions in which services are delivered. The impacts of water supply and sanitation (WSS) policies and programs range from greater efficiency in the utilities sector, improved access to higher quality services, health improvements, increased incomes and consumption, social and gender inclusion, and education improvements. Yet, to date we have few or no rigorous scientific impact<br>evaluations showing that WSS policies are effective in delivering many of the desired outcomes, except for health.
