A report has been published by the NRFA titled “Derivation of the UK National and Regional Runoff series”. The national and regional series are regularly featured in the reports published by the UK National Monitoring Programme where they are used to provide an objective framework within which to assess the exceptional nature of extreme hydrological episodes. The data also form an important component of the UK Government’s data reporting obligations to bodies such as European Environment Agency, Eurostat and OECD where they are published to inform international policy development. The report outlines the selection criteria for the index gauging stations, finalising the index networks and derivation of the daily outflow series for each domain. The national runoff series are considered a strategically important resource for indexing change – in circumstances where the impact of global warming on flood and drought risk across the UK remains high on both scientific and political agendas.