*1.2. Aim of This Paper*

Hydroinformatics has considerable advances to show across the entire water cycle, however it would be beyond the scope of this paper to include a review of all contributions in the field, thus the focus is limited to urban water issues and perspectives. This is because as urbanization continues to accelerate concentrating ever increasing demands for water services in cities and megacities around the world [7], and as urban water infrastructure is ageing and related investments are lagging behind [8], it is argued that the urban environment urgently needs smarter solutions based on hydroinformatics more than any other domain.

The current state of the art in (urban) hydroinformatics is mapped, proposing a narrative that connects several elements and strands of work together into a coherent whole. This narrative necessarily leaves aspects of hydroinformatics out, and where applicable, references to additional review work is added to assist the reader. Specifically, the paper highlights three main pieces of the hydroinformatics puzzle: Data, analytics and decision support (the last one in both its formal planning/design and societal/communication/engagemen<sup>t</sup> sense) in an effort to sugges<sup>t</sup> a way of thinking about the domain and to point towards a promising future.

**Figure 1.** The circular nature of hydroinformatics.
