Book excerpt: The aim of this report is to help improve the quality of the knowledge on the state of the world's water resources. In order to provide a basis for discussing the issues, FAO's Aquastat programme compiles existing quantitative and qualitative information on water resources, water use and irrigation by country. This report focuses on the work done through the Aquastat surveys to collect and analyse available information on water resources for all countries in the world. The report presents the concepts and methodology applied in order to compute country-level water resources data. It presents and analyses the key findings at both global and regional levels. It also discusses the limitations of the approach and the information gaps that remain.