This chapter describes how to design appropriate and cost-effective forest green infrastructure for water payment schemes to protect and improve water quality. It is structured by the main steps involved in establishing a payment scheme, starting with identifying the water issues and how tree planting and forest management can help, managing potential disbenefits and exploring multiple benefits, followed by scheme design, monitoring and communication. The approach is relevant to all actors involved in sustainable water management, farming and forestry, from policy makers, catchment planners and land managers to private investors, practitioners and local communities. We provide a common language and framework to help ensure schemes are successful in delivering water and other ecosystem services while minimising possible trade-offs (such as the potential for tree planting to reduce water resources).