Accessibility to clean and sufficient water resources for agriculture is key in feeding the steadily increasing world population in a sustainable manner. Nature-Based Solutions (NBS) offer a promising contribution to enhance availability and quality of water for productive purposes and human consumption, while simultaneously striving to preserve the integrity and intrinsic value of the ecosystems. Implementing successful NBS for water management, however, is not an easy task, since many ecosystems are already severely degraded and exploited beyond their regenerative capacity. Furthermore, ecosystems are large and complex and the many stakeholders involved may have conflicting interests. Hence, implementation of NBS requires a structured and comprehensive approach that starts with the valuation of the services provided by the ecosystem. The whole set of use and non-use values, in monetary terms, provides a factual basis to guide the implementation of NBS, which is ideally based on transdisciplinary principles, i.e. complemented with scientific and case-specific knowledge of the ecosystem in an adaptive decision-making process that involves the relevant stakeholders.This discussion paper evaluated twenty-one NBS case studies using a non-representative sample, to learn from successful and failed experiences and to identify possible causalities among factors that characterize the implementation of NBS. The case studies give a minor role to valuation of ecosystem services, an area for which the literature is still developing guidance. Less successful water management projects tend to suffer from inadequate factual and scientific basis and uncoordinated or insufficient stakeholder involvement and lack of long term planning. Successful case studies point to satisfactory understanding of the functioning of ecosystems and importance of multi-stakeholder platforms, well-identified funding schemes, realistic monitoring and evaluation systems and endurance of its promoters.
