Subregional and downscaled global scenarios of nutrient transfer in river basins: Seine‐Somme‐Scheldt case study

In an attempt to downscale the global prospective scenarios established by the Millennium Ecosystem Assessment to the level of three individual watersheds (the Seine, Somme, and Scheldt rivers), we examined the application of the regional RIVERSTRAHLER model, based on a mechanistic representation of in‐stream processes, in tandem with the semiempirical Global Nutrient Export from Watersheds (NEWS) model, by downscaling the input data of the latter into information required by the former. Overall, the model simulates the major trends of the changes that occurred in 1970–2000, although with some discrepancies revealing the weakness of certain hypothesis in the global approach. For the future, the prediction is a significant decrease in total nitrogen and phosphorus fluxes into the sea compared to those of 2000. We showed the benefits of combining a process‐based approach of nutrient transfer at the local scale with the use of global‐scale models for integrating the development of socioeconomic driving forces acting at the global level.