Increasing urbanization poses challenges, including water scarcity, insecurity, and loss of ecosystem services. In light of the increasing pressure on water resources worldwide, integrating decentralized approaches into existing infrastructure is essential for sustainable, efficient water resource management and reuse, establishing a circular water economy. Urban surface and groundwater are polluted, affecting quality of life, ecology, and land values. Chemical and biological hazards from inadequately treated water are growing concerns, especially with micropollutants and microplastics. Nature-Based Solutions for water treatment can complement grey infrastructure in urban environments, providing improved water quality, flood risk reduction, ecological connectivity, and attractive urban landscapes. Despite their potential, large-scale integration remains limited, as noted in the European Green Deal. Decision-makers often lack strategic tools, and technical knowledge gaps exist about system performance and response to climatic fluctuations. From an economic perspective, financing to stimulate rapid uptake of these NBS must look beyond private sector investment and towards spatial planning, regulation, and tax incentives. Tailored urban water management scenarios and frameworks are needed to help private stakeholders implement them citywide. MULTISOURCE has demonstrated a range of enhanced natural treatment systems for urban water and developed innovative tools, methods, and business models that support citywide integration of NBS for water treatment. The project has delivered new knowledge on contaminant removal, co-creation demand-driven tools, policy recommendations including three policy briefs, and a publication on mainstreaming gender inclusivity, thus reducing barriers to sustainable urban water management.
