Large investments currently being made in freshwater restoration in New Zealand require comprehensive monitoring programmes to support change detection and demonstrate value for money. The concept of Te Mana o Te Wai is embedded in the National Policy Statement for Freshwater Management (NPS-FM, 2020) and identifies the importance of freshwater and the need for healthy ecosystems to sustain life. The NPS-FM requires that the quality of freshwater be maintained, or improved where it is degraded, and introduces additional monitoring and reporting requirements for management authorities. In this context, land stewards need confidence that improvements in the state of the freshwater resource are identified robustly and in a timely manner, and that causal links can be established between management actions and freshwater outcomes. This Our Land and Water National Science Challenge research is a national (NZ) programme that aims to develop a range of tools and resources to: (1) assess the performance of existing monitoring networks and (2) suggest how the existing network may be augmented to optimise its likelihood of detecting changes from freshwater restoration actions, using both mātauranga Māori (traditional knowledge systems) and biophysical indicators. The research covers rivers, lakes and groundwater systems. Monitoring location, frequency, duration, technologies, relative cost and likelihood of detecting change are key parameters in the monitoring design optimisation. We present an overview of the programme and how tools first developed at the national scale can be applied at the catchment and sub-catchment scale using case studies.