Nature-based solutions of different spatial scales to improve the urban water cycle

The urban water cycle has traditionally been designed by engineering concepts of recollection, conveyance and centralized treatment of storm and waste waters. These concepts of a “drained city” have led to an optimization of urban space for housing and vehicle transport but at the cost of urban ecology and rivers due to high degrees of surface sealing, piping and channelization of (natural) water flow paths. With the implementation of Nature-based solutions in form of Green Infrastructures at three spatial scales (1 in-situ as source control of surface runoff, 2 at decentralized undeveloped urban free spaces and 3 along urban streams), the inter- and transdisciplinary research group SEE-URBAN-WATER challenges this traditional approach. The implementation of these Green Infrastructures is characterized by a process of Co-Design with local residents and other stakeholders in order to achieve a high degree of multi-functionality. This multi-functionality includes a technically sound design to reduce surface runoff and treat waste water, social-acceptance through including functionalities of direct benefit to the local residents and improvements of the ecological status of urban spaces and streams. In this manner, the implementation of Green Infrastructures addresses societal challenges more effectively and adaptively than merely technical solutions, while simultaneously providing human well-being and biodiversity benefits. In this contribution, the transdisciplinary process of site selection, design and implementation of pilot measures of Green Infrastructure in the district of Llorente in Costa Rica is presented. Different design alternatives and how they have been co-designed are discussed. Additionally, a concept is introduced of how the multi-functionality of the three spatial scales of Green Infrastructures and the differences of ecological and social functions of them relate to each other. Finally, difficulties and important steps of this process are addressed as well as recommendations for replication of similar processes at other sites are highlighted