Watercourse biology

A large proportion of the waterbodies in the Swiss Plateau can only fulfil their role as habitats for animals and plants to a limited extent, as a biological assessment of streams and small rivers shows. The species composition in large rivers is also strongly impacted by human activity and invasive alien species. The Red Lists give a clear indication of how the quality of waterbodies is severely compromised; over 50 per cent of all species living in and around them are endangered or already extinct.

Biological assessment of streams and rivers

The National Surface Water Quality Monitoring Programme (NAWA) is a comprehensive study into the biology of around one hundred watercourses. Diatoms (microalgae), macrozoobenthos (small organisms living at the bottom of the watercourse), aquatic plants and fish are the bioindicators used to assess how well a watercourse fulfils its function as a habitat for animals and plants and whether the ecological objectives of the Water Protection Ordinance – that habitats of aquatic organisms should be near-natural and rich in biological communities – are being attained.
In a broader sense, the biological studies of the Upper Rhine conducted since the early 1990s under the International Commission for the Protection of the Rhine (ICPR)'s biology monitoring programme also form part of NAWA.

Streams and small rivers widely fail to meet ecological targets

The quality of streams and rivers is particularly poor when assessed on the basis of the indicators 'fish' and 'aquatic plants'. Both indicators react to a number of different stressors and therefore well reflect the degree of anthropogenic influences and their complex interplay. Taking all indicators together, a comprehensive assessment of the ecological status of watercourses can be made. The overall state of a watercourse section is determined by the indicator with the worst rating. This worst-case scenario shows that over 60 per cent of the watercourses studied do not meet the ecological objectives of the Water Protection Ordinance. Taking only those where fish is one of the bioindicators, over 70 per cent can be shown to be in an unsatisfactory state. If we consider only those watercourses where all four biological indicators can be surveyed, then up to 80 per cent of the sites are in a poor state. In other words, a large proportion of the streams and rivers studied do not provide a functional habitat for animals and plants. These watercourses thus do not meet the ecological objectives of the Water Protection Ordinance.
There are particularly severe deficits in the intensively used Swiss Plateau, where the watercourses are structurally impaired and fish are unable to migrate along them in many places. Small watercourses are under particular pressure from nutrient run-off from agriculture; in medium-sized rivers, micropollutants from wastewater treatment plants (WWTPs) affect aquatic life.

Biologische Indizes

The biological indices assess different factors in water quality, and so there is some considerable difference between the degree of target achievement depending on the index. Diatoms indicate the nutrient load, macrozoobenthos the water quality and habitat diversity, and aquatic plants and fish reflect the combination of different stressors. Data: NAWA TREND 2019

Biologische Indikatoren

The more biological indicators are used to assess a watercourse, the worse the assessment becomes. The overall state is determined in each case by the indicator with the worst rating a) Assessment of all NAWA TREND monitoring sites using two to four indicators; b) Assessment using three indicators (diatoms, macrozoobenthos and fish); c) Assessment using four indicators (diatoms, macrozoobenthos, fish and aquatic plants). Data: NAWA TREND 2019

Major deficits also in the biology of large rivers

The communities of macrozoobenthos, aquatic plants and fish are also severely deficient in Switzerland's large rivers. This is the evidence from both the regular Upper Rhine surveys and cantonal campaigns.
Long-distance migrants such as salmon have been extinct in Switzerland for quite some time, most likely because of the many obstacles to migration posed by power plants. Other migratory fish are highly endangered. Stocks of fish specialised for free-flowing and cool rivers are also declining. The composition of aquatic plants is also strongly impacted by water quality and river structure. Many important colonies of taller aquatic plants have disappeared where rivers have been artificially channelled. Furthermore, dammed areas containing lots of sand and mud are colonised by algae and aquatic plants that are untypical for rivers.
Macrozoobenthos communities are dominated by generalists and alien species. Specialised species have become very rare – for example, those whose habitat is the calm water near a river bank or in a water meadow.

The results of the studies conducted in the Upper Rhine and Aare can be found under Documentation.

Aquatic life is under threat

The ecological deficits discussed here are borne out by the fact that biodiversity in and around lakes and rivers has declined sharply or is highly endangered. Over 50 per cent of all species living in and around water are endangered or already extinct. Invasive alien plants and animals, some of which are spreading rapidly in large rivers and lakes, are putting additional pressure on native species. Rich biodiversity is essential for ecosystems to remain resilient to environmental changes such as climate change and the presence of alien species.

Further information

Documents

NAWA: Messstellendokumentation (PDF, 112 MB, 15.05.2018)Chaix O., Stalder P., Hürlimann J. 2018: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Messstellendokumentation (Startphase 2012–2013) im Auftrag des BAFU

Fish

NAWA - TREND Biologie - Streckendossiers Fische 2019 (PDF, 26 MB, 28.02.2022)Beschreibung der Befischungsstrecken im Auftrag des BAFU

NAWA TREND Biologie – Besatzkoordinationskarten Fische 2019 (PDF, 30 MB, 08.03.2022)Ninck L., Dönni W., Gouskov A., Guthruf J., Périat G., Vonlanthen P., Zaugg C. 2021: NAWA TREND Biologie, 3. Kampagne (2019), Karten Besatzkoordination Fische. Im Auftrag des BAFU.

NAWA-Fachbericht Modul Fische 2012-2013 (PDF, 5 MB, 16.05.2014)Dönni W. und Guthruf J. 2014: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Modul Fische (Startphase 2012–2013). Expertenbericht im Auftrag des BAFU

NAWA-Modul Fische 2012-2013 Quantitative Erhebungen (PDF, 567 kB, 23.06.2014)Dönni W., Guthruf J., Riedl C., Werner S. und Zaugg C. 2014: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Modul Fische: Quantitative Erhebungen (Startphase 2012–2013). Auswertungen im Auftrag des BAFU

Macrozoobenthos

NAWA-Fachbericht Modul Makrozoobenthos 2015 (PDF, 1 MB, 28.02.2017)Stucki P. und Knispel S. 2017: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Modul Makrozoobenthos 2015. Expertenbericht im Auftrag des BAFU

NAWA: Rapport technique Macrozoobenthos 2011-2014 (PDF, 1 MB, 31.05.2015)Stucki P., Knispel S., Vicentini H. et Wagner A. 2015: NAWA TREND Biologie. Rapport Sectoriel Macrozoobenthos, campagne 2012, campagnes complémentaires 2011‐2014. Sur mandat de l’OFEV

Diatoms

NAWA-Fachbericht Modul Diatomeen 2015 (PDF, 1 MB, 12.07.2017)Hürlimann J. und Straub F. 2017: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Modul Diatomeen und äusserer Aspekt 2015. Expertenbericht im Auftrag des BAFU

NAWA-Fachbericht Modul Diatomeen 2011-2013 (PDF, 3 MB, 23.06.2014)Hürlimann J. und Straub F. 2014: NAWA TREND Biologie 2011-2013, Teil Diatomeen. Expertenbericht im Auftrag des BAFU

NAWA: Äusserer Aspekt (PDF, 566 kB, 15.05.2018)Hürlimann J., Küng M., Straub F. 2014: NAWA TREND Biologie 2011-2013, Teil Äusserer Aspekt. Erfassung der Feldprotokolle und erste Analysen. Kurzbericht im Auftrag des Bundesamtes für Umwelt

Macrophytes

NAWA-Fachbericht Modul Makrophyten 2015: Anhänge A-E (PDF, 1 MB, 13.09.2019)Roth E. und Müller N. 2017: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Modul Makrophyten 2015: Anhang. Expertenbericht im Auftrag des BAFU

NAWA-Fachbericht Modul Makrophyten 2015: Anhang F (PDF, 208 MB, 13.09.2019)Roth E. und Müller N. 2017: Biologische Erhebungen der Nationalen Beobachtung Oberflächengewässerqualität (NAWA), Modul Makrophyten 2015: Anhang. Expertenbericht im Auftrag des BAFU

NAWA-Fachbericht Modul Makrophyten 2012 (PDF, 958 kB, 16.05.2014)Roth E. 2013: NAWA TREND Biologie
Teilbereich Makrophyten 2012. Expertenbericht im Auftrag des BAFU

NAWA-Fachbericht Modul Makrophyten 2012: Anhang F (PDF, 34 MB, 16.05.2014)Roth E. 2013: NAWA TREND Biologie
Teilbereich Makrophyten 2012: Messstellendossiers im Auftrag des BAFU

Contact
Last modification 23.08.2022

Top of page

https://www.bafu.admin.ch/content/bafu/en/home/topics/water/info-specialists/state-of-waterbodies/state-of-watercourses/water-quality-in-watercourses/watercourse-biology.html/