Currently, the world is facing resource scarcity as the environmental impacts of human intervention continue to intensify. To facilitate the conservation and recovery of ecosystems and to transform cities into more sustainable, intelligent, regenerative, and resilient environments, the concepts of circularity and nature-based solutions (NbS) are applied. The role of NbS within green infrastructure in urban resilience is recognised, and considerable efforts are being made by the European Commission (EC) to achieve the European sustainability goals. However, it is not fully evidenced, in an integrated way, which are the main NbS implemented in the urban environment and their effects. This article aims to identify the main and most recent NbS applied in urban environments at the European level and to analyse the integration of different measures as an innovative analysis based on real cases. For this purpose, this work presents a literature review of 69 projects implemented in 24 European cities, as well as 8 urban actions and 3 spatial scales of implementation at the district level. Therefore, there is great potential for NbS adoption in buildings and their surroundings, which are still not prioritized, given the lack of effective monitoring of the effects of NbS.

In the context of freshwater scarcity, effective water resource management is essential. This study explores techniques to optimise the use of local water sources and promote conservation, proposing a model to balance the supply and demand of non-potable water in urban environments. The model serves as an alternative or complement to public water supplies, particularly in drought-prone regions. Through a qualitative analysis of national and international regulations, specifications, and technical standards, this research identifies key trends in the use of alternative water sources and highlights knowledge gaps in urban water management, which are addressed through the proposed model. The study emphasises the transition from Nearly Zero Water Buildings (NZWBs) to Urban Water Communities (UWCs) as a sustainable and resilient solution, integrating decentralised water management approaches and resource recovery from wastewater. Additionally, a case study in a Portuguese urbanisation area illustrates the application of these principles and assesses their potential in real-world scenarios. The findings contribute to the development of comprehensive guidelines and public policies for sustainable urban water management, supporting the implementation of decentralised and integrated solutions that enhance resilience, water security, and resource efficiency.