Developing a graph-based, object-oriented urban water cycle simulation engine to explore circular water options

This study demonstrates the development and use of a graph-based, object-oriented urban water cycle simulation engine able to model: (a) arbitrary information flows through graph edges and (b) arbitrary circular water technologies, either at the supply or the demand side, through graph nodes. The concept, built in Python, is demonstrated for the information flows of water quantity and (conservative) quality in a real-world application at a neighbourhood spatial scale in the Netherlands, where it delivers quantitative insights that agree with previous research works, while significantly reducing the complexity of earlier procedural modelling structures. Structural aspects and limitations are discussed, including slower runtimes but drastically improved code coherence and readability due to the use of OOP and high-level graph network management libraries. The application shows the potential of this engine to be used as a modus universalis for designing circular water options and understanding their role within the complex socio-technical urban water system.