This article asks whether urban water systems can foster commoning and collective self-organisation. The Water Gardens in Hemel Hempstead is analysed as a social–ecological system in which landscape design, hydrological functions, public use and community organisation interact.

The study combines Ostrom’s framework with archival research, observation, interviews and social-media topic and network analysis. It identifies leadership, recreation, knowledge sharing and online networking as levers that can strengthen collective stewardship.

The contribution extends urban-metabolism research toward the governance of shared resources. It shows that the capacity of infrastructure to support commoning depends on both its physical configuration and the relationships through which people interpret and care for it.