NAPSEA: N and P from Source to Sea
The NAPSEA project supported national and local authorities in selecting effective measures and policies to reduce nutrient loads, while building societal support for their implementation.
The project focused on the Wadden Sea catchment area, with case studies covering the Rhine, Elbe and Hunze catchments, as well as the Wadden Sea itself. It took an integrated source-to-sea approach to address nutrient pollution, bringing together three complementary perspectives: governance and social acceptance, nutrient pathways and measures, and ecosystem health.
Ecosystem health perspective
Water quality objectives from source to sea are not aligned at the operational level. Differences persist between legal frameworks - notably the Water Framework Directive and Marine Strategy Framework Directive - and between countries. In addition, current indicators are highly technical and less accessible to a wider audience.
NAPSEA addressed this by proposing alternative indicators and objectives, such as the recovery of seagrass in the Wadden Sea and submerged vegetation in Zuidlaardermeer. These habitats are highly valued for their biodiversity and respond well to reductions in nutrient pollution.
Exploring effective nutrient management strategies
Germany is an important partner for the Netherlands, given the transboundary nature of nutrient flows and ongoing collaboration on intercalibration (calibration between two or more instruments or datasets). Within NAPSEA, this collaboration generated valuable knowledge and insight into effective nutrient management strategies.
The project assessed both existing and potential additional measures, as well as the societal support for them. It evaluated different combinations of measures against thresholds for a range of ecological indicators, providing a clear picture of both their costs and their ecological benefits.
Main conclusions and recommendations
- Currently planned nutrient reduction measures are insufficient to achieve all the proposed ecological objectives; more stringent measures are needed.
- Climate change has a significant impact on riverine nutrient loads, particularly in the Elbe.
- Increase transparency on the aims and narratives of nutrient reduction targets.
- Align and expand monitoring locations for water flows and nutrient concentrations to support reliable nutrient load estimates.
- Adopt an integrated source-to-sea approach to better understand nutrient dynamics and define effective measures.
- Take climate change impacts, adaptation measures and biodiversity policies into account in nutrient management.
Importance for Rijkswaterstaat and the Ministry of Infrastructure and Water Management
Inconsistencies in nutrient objectives between marine and inland waters have been recognised for several years. NAPSEA clarified where the Dutch and German implementations of EU policies diverge and highlighted the interdependence between the two countries. The project’s results support continued dialogue and collaboration, and underline the importance of designing effective and coherent measures to achieve the ecological objectives in the areas concerned.
Period
October 2021 - September 2025
Programme
Horizon Europe Framework Programme
Project website
Partners
Rijkswaterstaat, Deltares (project coordinator), Helmholtz - Zentrum Hereon GmbH, Fresh Thoughts Consulting GmbH, Helmholtz Centre for Environmental Research, Umwelt Bundesambt, Nutriënten Management Instituut.
