Appropriate data management as the basis of effective performance reporting is crucial if sector institutions are to track whether they achieve their objectives. This paper shows how a post process of readily available data to construct water poverty maps can be used to identify effectively the most water poor communities, and thus improve the targeting of sector development policies and projects. To this end, water poverty takes its definition from the Water Poverty Index, which combines biophysical, social, economic and environmental data in one single and comparable number to produce a holistic and user-friendly tool for policy making. The study is based on a comprehensive record of the water sources developed by UNICEF in Turkana District, in Kenya. The main conclusion is that such an index allows decision-makers to determine and target priority needs for interventions in the water sector, while assessing the impacts of sector-related development policies.