## There is [a newer version](https://doi.org/10.25678/0008KG) of this dataset. **There is [an older version](https://doi.org/10.25678/0006MV) of this dataset.** The “National Long-term Surveillance of Swiss Rivers” (NADUF) program was initiated in 1972 as a cooperative project between three institutes: + [Federal Office for the Environment (FOEN)](https://www.bafu.admin.ch/bafu/en/home.html) + [Swiss Federal Institute of Aquatic Science and Technology (EAWAG)](https://www.eawag.ch) + [Swiss Federal Institute for Forest, Snow and Landscape Research (WSL)](https://www.wsl.ch/en.html) (since 2003) The following institutes participated later: + [Amt für Umwelt und Energie des Kantons Basel-Stadt (AUE)](https://www.aue.bs.ch) + [Federal Institute of Metrology (METAS)](https://www.metas.ch/metas/en/home.html) With the NADUF program, the chemical-physical state of Swiss rivers as well as intermediate-term and long-term changes in concentration are observed. Furthermore, it provides data for scientific studies on biological, chemical and physical processes in river water. The NADUF network serves as a basic data and sampling facility to evaluate the effectiveness of water protection measures and for various scientific projects. ### Data from 2020 to 2021 The physical data for the years 2020 and 2021 are provisional. Accordingly, the chemical data are not yet definitive.