Water quality is a critical challenge in Asia in the context of growing industrialization, urbanization and climate change. Nature-based solutions (NBS) could play an important role in reducing urban water pollution while generating multiple co-benefits that could make cities more livable and resilient. In this regard, a number of pilot and demonstration projects have been set up to explore their potential across cities in Asia. Their effectiveness, however, has not been adequately documented and how they can be sustained, replicated and up-scaled remains poorly understood. This project aims to contribute to addressing those questions by compiling and analyzing the experiences of existing pilot and demonstration projects in six cities in Southeast Asia (two in each Sri Lanka, Philippines and Vietnam) and developing and testing a nature-based water treatment pathways methodology and guide that can be used to support the establishment, maintenance and scaling of nature-based water treatment through collaborative action research and multi-stakeholder consultations. The project will be implemented in close collaboration with relevant international networks and will be informed by international experiences with the integration of nature-based water treatment in urban water management and planning from Australia and Europe.