The e-handbook is a decision-support toolkit for city decision makers and stakeholders in the urban water ecosystem. It contains information about smart planning, governance, engineering, and digital solutions for water saving and water reuse. The e-handbook consists of four thematic catalogues: "Smart tools for assessing the potential of urban water use", "Innovative engineering and nature-based solutions for circular water consumption", "Promoting smart water management tools", and "Novel digital tools promoting water efficiency among citizens/consumers".