Nitrogen sources, retention and exports in the Hunze, Rhine and Elbe river basins

The study focused on simulating the long-term flux of Nitrogen (N) from source to mouth in the Hunze, Rhine, and Elbe river basins. This was achieved by integrating models that encompass hydrology, nutrient input to surface water, and in-stream retention. The aim was to comprehensively understand the spatial and temporal distribution of N sources, soil budget, delivery to streams, and in-stream retention across these basins. Notably, significant improvements in water quality were observed in these rivers following decades of efforts aimed at reducing nutrient pollution from agricultural and sewage sources. These improvements have brought the water quality close to the EU standard of 2.5 mg/L. However, it was observed that post-2000, the decline in N concentration stagnated. This study elucidates the long-term dynamics of N sources and their contribution to surface water in the three basins. The findings, which offer a spatially explicit nutrient source allocation, are crucial for strategically targeting nutrient reduction policies to foster sustainable water quality management.