The aim of WP4 is to apply the SWAT+ model to the six river basins to quantify daily concentrations and loads of N and P and nutrient sources, pathways, and sinks. A comparison of SWAT+ with existing national models will be performed and the model’s potential as a harmonised tool for the region will be assessed. Nutrient reduction targets will be defined based on the difference between simulated nutrient concentration and loads and safe ecological boundaries, taking into consideration both current and future climate conditions.