Urban water balance studies support sustainable resource management, climate change adaptation, and flood risk reduction by optimizing water allocation and protecting groundwater quality. They act as the first step in improving communication between experts, decision-makers, and users, and need to be based on high-quality groundwater monitoring, mapping, data sharing, and good planning practices. The lack of a solid theoretical and empirical basis for decision-making is not only an information vacuum but is potentially a serious hazard creating problems. Such urban-scale hydrogeological problems are caused by the unobserved and unanticipated interaction between groundwater and underground infrastructure. Addressing these problems requires coordinated action from water utilities, geological surveys, urban planners, and hydrogeologists, especially in view of climate change and green infrastructure initiatives. Effective management can be achieved by implementing a dedicated municipal service in charge of data and decision-making on geology, groundwater, and underground infrastructure elements and networks. Significant policy improvements and related technical cooperation between institutions are the basis for success in implementing appropriate groundwater management in cities. This depends on implementing an interdisciplinary, multi-stakeholder approach with a shared understanding of the issues.