New guidance supports source-to-sea water management

The new guidance was developed as part of the UN Water Convention and offers concrete steps and recommendations to tackle water pollution, biodiversity loss, and climate impacts. It supports governments, river and sea basin managers, and technical experts responsible for managing shared waters and interconnected ecosystems such as deltas, estuaries, and marine areas. The 1992 UN Water Convention includes commitments to protect transboundary land, water, and sea connections. Europe, for example, has regional river commissions for the Rhine, Meuse, and Danube that work closely within the framework of the Water Convention.

Source-to-sea management offers environmental benefits such as restored aquatic habitats or increased carbon sequestration, social benefits such as reductions in waterborne diseases or greater social cohesion, and economic benefits such as increased value of fisheries or a more attractive tourism industry. It can also facilitate peace and security benefits by strengthening regional integration and reducing political tensions through increased coordination on shared objectives.

Sonja Koeppel, Secretary of the Water Convention

Three Case Studies from Our Practice

Transformative Transboundary Water Management in the Rhine (Europe)

This case describes how climate change and socio-economic developments affect water flows, sediment transport, and water quality in the Rhine basin. The International Commission for the Hydrology of the Rhine Basin (CHR) conducts studies on glacier melt, sea level rise, and changing water demands. The results show that transboundary cooperation and adaptive water management are essential to address future challenges.

Characterizing Plastic Waste Pollution from Source to Sea in Indonesia (Asia)

This study used hydrological data and advanced models to map the quantity and distribution of plastic pollution in Indonesia. The analysis covered more than 500 districts and identified where plastic enters the environment and eventually reaches the sea. The results provide a detailed basis for policy and targeted interventions to tackle plastic pollution at the source.

Narrowing the Data and Knowledge Gap on Hazardous Chemicals in the Danube River Basin (Europe)

The Danube Hazard m3c project developed a chemical emissions model and collected data on hazardous substances in the Danube region. Through collaboration between eight countries and various research institutions, a scientifically grounded basis was created for policy development and measures against chemical pollution. The project strengthened the link between science and policy and delivered practical tools for transboundary environmental management.

I’ve had positive experiences with cross-border collaboration, for example with governments and research institutes in the Rhine basin. Only through joint actions can we work toward sustainable and widely supported solutions for water distribution and management. People, nature, and the economy along the entire river benefit from this.

Judith ter Maat, expert surface water and delta management

Source-to-Sea Approach

The guidance is a call to action and offers support for deeper collaboration between river basins worldwide. This approach was recently endorsed at the 2025 International Ocean Conference in Nice.

Deltares contributes globally to the source-to-sea approach by developing knowledge on how pollutants move through the environment, where they affect resources for people and nature, and which substances end up in the sea, soil, or groundwater. Some substances break down and disappear along the way, while others reappear elsewhere. We also conduct experiments to expand this knowledge. To expand the knowledge base, we work closely with the Source-to-Sea Platform and several European consortia. The new guidance is also an example of how we do this.