Management of urban waters with nature-based solutions in circular cities—exemplified through seven urban circularity challenges

Hasan Volkan Oral*, Matej Radinja, Anacleto Rizzo, Katharina Kearney, Theis Raaschou Andersen, Pawel Krzeminski, Gianluigi Buttiglieri, Derya Ayral-Cinar, Joaquim Comas, Magdalena Gajewska, Marco Hartl, David C. Finger, Jan K. Kazak, Harri Mattila, Patrícia Vieira, Patrizia Piro, Stefania Anna Palermo, Michele Turco, Behrouz Pirouz, Alexandros StefanakisMartin Regelsberger, Nadia Ursino, Pedro N. Carvalho

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Nature-Based Solutions (NBS) have been proven to effectively mitigate and solve resource depletion and climate-related challenges in urban areas. The COST (Cooperation in Science and Technology) Action CA17133 entitled “Implementing nature-based solutions (NBS) for building a resourceful circular city” has established seven urban circularity challenges (UCC) that can be addressed effectively with NBS. This paper presents the outcomes of five elucidation workshops with more than 20 European experts from different backgrounds. These international workshops were used to examine the effectiveness of NBS to address UCC and foster NBS implementation towards circular urban water management. A major outcome was the identification of the two most relevant challenges for water resources in urban areas: ‘Restoring and maintaining the water cycle’ (UCC1) and ‘Water and waste treatment, recovery, and reuse’ (UCC2). s Moreover, significant synergies with ‘Nutrient recovery and reuse’, ‘Material recovery and reuse’, ‘Food and biomass production’, ‘Energy efficiency and recovery’, and ‘Building system recovery’ were identified. Additionally, the paper presents real-life case studies to demonstrate how different NBS and supporting units can contribute to the UCC. Finally, a case-based semi-quantitative assessment of the presented NBS was performed. Most notably, this paper identifies the most typically employed NBS that enable processes for UCC1 and UCC2. While current consensus is well established by experts in individual NBS, we presently highlight the potential to address UCC by combining different NBS and synergize enabling processes. This study presents a new paradigm and aims to enhance awareness on the ability of NBS to solve multiple urban circularity issues.

Original languageEnglish
Article number3334
JournalWater (Switzerland)
Issue number23
Publication statusPublished - 24 Nov 2021

Bibliographical note

Funding Information:
Acknowledgments: The work was carried out within the COST Action CA17133 Circular City (“Implementing nature-based solutions for creating a resourceful circular city”, (accessed on 12 April 2021), duration 22 October 2018—21 October 2022). COST Actions are funded within the EU Horizon 2020 Programme. The authors are grateful for the support. Additionally, authors would like to thank the following colleagues that have actively participated in at least one workshop and respective discussions, and/or contributed to the collection of examples: Antonia Lorenzo (BioAzul), Attila Toth (Slovak University of Agriculture in Nitra), Fabio Masi (IRIDRA) and Natasa Atanasova (University of Ljubljana). Patrícia Vieira is grateful for her research contract funded by Fundação para a Ciência e Tecnologia (FCT) and project CENTRO-04-3559-FSE-000095—Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). Joaquim Comas and Gianluigi Buttiglieri acknowledge the CLEaN-TOUR project (CTM2017-85385-C2-1-R) from the Spanish Ministry of Economy and Competitiveness, Generalitat de Catalunya through Consolidated Research Group 2017-SGR-1318 and funding from CERCA programme/Generalitat de Catalunya.

Funding Information:
Funding: The APC was funded by COST CA 17133.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Other keywords

  • Blue-green infrastructure
  • Climate change and mitigation
  • Sustainable water management
  • Urban circularity challenges
  • Water reuse


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