Department Surface Waters - Research and Management

The ETH-Board appoints Carsten Schubert as a new member of the Directorate of Eawag, the aquatic research institute.

Sprawling carpets of floating plants are the result of too many nutrients. However, they could become part of solution strategies, Eawag researchers show.

When the wind on Lake Biel blows from the south-west and it rains heavily, large quantities of sediment are washed out of the River Aare into the lake. Since the south-west wind also influences the circulation in the lake, the wind direction determines to a large extent where the sediment is deposited in the lake, namely along the eastern shore towards Biel – an important finding for identifying areas at risk of landslides.

The findings of a new measurement campaign on Lake Kivu in Africa show that, contrary to previous assumptions, the methane concentration in the water is relatively stable or increasing only very slowly. Therefore, the risk of a sudden gas eruption from the lake is currently not increasing.

Whether a lake was once polluted with excess nutrients is reflected even decades later in the community of bacteria living on these nutrients in the sediment. However, there is still surprisingly little research into how microbes in the sediment cooperate.

Adaptation to warmer environmental conditions may increase the resistance of viruses, making them harder to be inactivated. This is the finding of a new study involving Eawag. Global warming could therefore make it more difficult to combat viruses.

Process Engineer Adriano Joss from Eawag water research institute has been working for many years on wastewater treatment plants and the removal of micropollutants from water. Together with Ralf Kägi, Head of the Eawag Particle Laboratory, he has compiled the current status of knowledge on microplastics. In an interview, he presents the most important findings. We have recently posted detailed information on the website “Microplastics in the environment”.

Researchers from Agroscope, Eawag, University of Bern and ETH have developed a method for the comprehensive detection of organic pollutant residues in soils and sediments. Initial results show that, in addition to known substances, there are also a number of substances detected for the first time.

126 Swiss researchers, including 6 from Eawag, want to draw the attention their Swiss compatriots to the scientific evidence showing the link between the emergence of pandemics and human disturbance of the natural environment.

In many places in Switzerland, rivers, streams and lakeshores are being restored. The new practice documentation “Evaluating the outcome of restoration projects” by Eawag and FOEN provides the basis for joint learning across project boundaries.

There is a flip side to the annoying blankets of pollen found on cars, garden furniture and other surfaces: when it comes to satellite images, pollen on lakes reveals currents that are otherwise only visible in computer models. This makes the waterbody researchers and remote sensing experts very happy.

Contaminated waste water often flows into rivers and streams after heavy rains. Antibiotic-resistant bacteria thus also enter the waters. Eawag is researching exactly which ones and in what amounts as part of a national research programme.

The theme to this year’s UNESCO World Water Day is “Water and Climate Change”. Environmental scientist Martin Schmid, who is Head of the Eawag Group Applied System Analysis in the Surface Waters Department, talks about how climate change is impacting on waterbodies in Switzerland.

Pesticides in sediments cause adverse effects on benthic organisms. This was shown by a monitoring study conducted by the Ecotox Centre and Eawag on five streams in agricultural areas. Crustaceans were particularly affected. Concentrations of several insecticides, including chlorpyrifos and the pyrethroid cypermethrin, exceeded effect thresholds, indicating impaired sediment quality.

The Global Science Film Festival took place from the 15th to the 17th November in Zurich. In addition to films and short films, videos produced by scientists were shown – amongst those, a film by Helmut Bürgmann and Davide Ciccarese.

The energy strategy calls for a further expansion of hydropower. This puts pressure on Swiss water bodies and water landscapes. At today's Eawag Info Day, some 200 experts from practice, research and administration will discuss how the various interests in water can be met in a sustainable manner and where the competition between these interests calls for priorities to be set. The Eawag researchers will demonstrate that it is not only a question of technical solutions, but also of social acceptance, for example when measures in favour of water ecology lead to an increase in the price of electricity.

The summer heat has reached Switzerland and cooling down in the lake certainly does no harm. On the website "Meteolakes" you can find out how refreshing a dip in Lake Zurich will be at the moment, the next hours and days.

Since the last ice age, stickleback have managed to emerge from the sea to colonise many freshwater waterbodies. Genetic analysis by Eawag researchers and colleagues from the University of Bern and the National Institute of Genetics in Shizuoka, Japan, now demonstrate that they achieved this thanks to additional copies of a metabolism gene.

Geologist Carsten Schubert has been appointed adjungt professor by the ETH Board. He is thus honoured for his research on biogeochemical cycles and for his teaching activities and doctoral training.

As of this week, “LéXPLORE”, a 100 metre research platform, is afloat on Lake Geneva. On board are countless radiosondes and sensors which should enable researchers at Eawag, EPFL and the Universities of Lausanne and Geneva to gain a better understanding of the ecological processes at work in Lake Geneva as well as the interactions between the water and the atmosphere.

Antibiotic resistance genes are not completely eliminated by wastewater treatment. While some resistance genes are present in the influent, many others are found in activated sludge bacteria. A recent Eawag study shows that, rather than merely passing through, resistance genes are active and evolve within treatment plants.

When a population grows quickly and farms intensively, the environment often suffers. This is not only true today, but was also the case as early as Roman times. Evidence of this has been found by Eawag researchers in sediments in Lake Murten.

Mountain rivers swollen by heavy rainfall deposit large amounts of sediment in reservoirs. To prevent the loss of storage capacity, some reservoirs are equipped with bypass tunnels which convey sediment-laden waters to downstream reaches. The fact that such tunnels offer ecological benefits as well as economic advantages was shown, for example, by a study carried out on the Solis reservoir in Graubünden.

When does the poisonous blue alga reach its critical point and how does the lake react to heat waves? In the future, satellite pictures will answer these questions in real time. This is demonstrated by an Eawag researcher’s new dataset. 

Clear mountain lakes could change with ever greater frequency into milky soup in the future. Climate change is the guilty agent. This has been shown by a new study led by the University of Lausanne in collaboration with Eawag and the French National Agricultural Research Institute using the example of a French mountain lake.

Climate warming is not the only cause of temperature changes in lakes, rivers and other bodies of water. The use of waterbodies for heating and cooling also leads to increases or decreases in water temperature. There has been little research to date, however, on how this affects aquatic ecosystems. This lack of understanding has been highlighted by a recent literature review carried out at Eawag and the University of Bern.

A long-term study of Switzerland’s major watercourses has been continuing for almost 45 years. An evaluation of the time series shows that as the climate is changing, so are geochemical processes. Most of the measuring stations show an increase in the concentrations of bicarbonate. The changes are caused by increases in temperatures, the presence of nutrients in the lakes and the acidity of the soil. On the other hand, following a peak in the late 1980s, nitrogen concentrations have been decreasing. The reasons for this are a reduced input of nitrogen in agriculture and improved elimination in wastewater treatment.

Eawag has studied how various pumped-storage hydropower scenarios affect temperature and water quality in the waterbodies concerned. In the case of Sihlsee, which serves as a reservoir for the SBB Etzelwerk plant, the question of withdrawal depth was found to be crucially important. The study also highlighted the fact that the assessment of environmental impacts largely depends on the definition of the reference state: whereas in natural lakes water is discharged from the surface, in reservoirs it is withdrawn from the lower layer. The environmental and aesthetic impacts of pumped-storage operations in the riparian zone were not examined in this study.

Commitment to teaching: Eawag scientist Bernhard Wehrli took over the post of Director of Studies in Environmental Sciences at ETH Zurich on August 1, 2018.

Eawag, the ETH Zurich and the University of Bern have developed a new instrument: the “Combined Vacuum Crushing and Sieving System” (CVCS). This device makes possible the extraction of minute water and noble gas inclusions that are thousands of years old from the pores of minerals in caves, without distortion by the present atmosphere.

Thanks to Copernicus – the EU Earth Observation Programme initiated in 2014 – environmental researchers now have access to vast amounts of high-quality satellite data. As this is also invaluable for aquatic research, Eawag is currently expanding its capacity in the area of remote sensing.

Black plastic balls, which aim to reduce evaporation losses from open-air reservoirs under drought conditions, are not quite as efficient as previously assumed. Considerable quantities of water are already used in their production. 

Small hydropower plants are often constructed on alpine streams, where they may have adverse impacts on sensitive ecosystems. Little is known, however, about the particular effects of individual plants, or the cumulative effects of multiple plants within the same river system. The current state of knowledge has now been reviewed in a study by Eawag researchers. 

Antibiotic resistance is widespread in bacteria spores and preserved for years, as shown by experiments at Eawag and the University of Neuchâtel.

Faced with polluted river water, rural communities or aid agencies often drill groundwater wells to obtain water supplies. But data collected systematically for the first time in the Amazon basin show that this “solution” can create new problems: the groundwater may contain elevated concentrations of arsenic, manganese and aluminium – up to 70 times over the recommended limit in the case of arsenic, and up to 15 times for manganese.

“A rolling stone gathers no moss.” This is the saying credited with giving the famous British rock band its name…but does it hold true from an ecological or hydraulic engineering perspective? 

If the climate heats up, the temperature in the uppermost layer of lakes will increase, the thermic layering will become more stable and last longer, and less oxygen will reach the depths – this is the present theory on the effect of climate change on lakes.

A research team from the Surface Waters Research and Management Department is investigating the earliest traces of human life in the tropical Pacific. In July 2017, the team undertook an expedition to Vanuatu in Melanesia. The researchers took sediment cores from the lakes and marshes on seven islands in order to test these for indications of the earliest human activities.

How much thermal energy from Swiss lakes can be exploited without having an impact on their ecosystems? Eawag was commissioned by the Swiss Federal Office for the Environment (FOEN) to estimate the potentials with the larger lakes and rivers.

The composition of cyanobacterial communities in peri-alpine lakes has become increasingly similar over the past century. Climate warming and a period of eutrophication have favoured in particular potentially toxic species which can adapt rapidly to environmental changes. These are the findings of an Eawag-led study analysing DNA extracted from sediment cores.

Although nutrient inputs to Swiss lakes are today much lower than they were before the introduction of phosphate precipitation at wastewater treatment plants and the ban on phosphates in detergents, many lakes are still affected by oxygen depletion – especially in the deeper waters.

Christian Stamm and Alfred Johny Wüest are lecturing along with other academics and practitioners in a new online course on “Water in Switzerland”, run by the University of Zurich. The course, addressed to the public, examines how this element affects various aspects of life in Switzerland.

Compared to other foodstuffs, Switzerland’s drinking water shows low levels of contamination with antibiotic-resistant bacteria or resistance genes. This was demonstrated in a study of eight drinking water systems carried out by Eawag researchers on behalf of the Swiss Gas and Water Industry Association (SVGW) and water suppliers.

According to a study funded by the Federal Office for the Environment, pesticides or transformation products can persist in soils for a decade or more. In the study, Eawag and Agroscope scientists analysed topsoil samples collected from 14 agricultural sites between 1995 and 2008 as part of the Swiss Soil Monitoring Network programme. 

A study just published by Eawag scientists shows that gold and silver each amounting to around CHF 1.5 million a year are lost via effluents and sludge from wastewater treatment plants in Switzerland. The concentrations measured do not pose risks to the environment – and recycling would not be economically worthwhile. However, the study also produced surprising findings on other trace elements in wastewater, including rare earth metals such as gadolinium and the heavy metal niobium.

Single-celled bacteria are capable of mixing water layers in lakes – not directly, by movement of their flagella, but by accumulating locally and thus increasing water density. The heavier water then sinks, creating circular currents. Researchers have now observed this process for the first time not just in the laboratory, but in a natural water body – Lake Cadagno (canton of Ticino).

If the wind blows away the warm surface waters of a lake, cold water flows in from the depths. As a result of this effect the temperature in Lake Geneva recently sank to 8 degrees. A project led by Eawag and EPFL had predicted this cooling event.

In freshwater lakes, large amounts of the greenhouse gas methane are oxidized by bacteria before it can be emitted into the atmosphere. A study in Lakes Rotsee and Zug has now shown that the bulk of this work is done, not by “classical” methane consumers, but by filamentous bacteria previously known only as contaminants of water supplies.

Micropollutants enter rivers and streams in effluents discharged from wastewater treatment plants (WWTPs). As well as having adverse impacts on individual species, these substances appear to alter aquatic ecosystem functions, such as litter decomposition. This was shown by a research project launched by Eawag in view of the planned upgrade of selected Swiss WWTPs to reduce micropollutant loads. The effects of the first upgrades are already evident. 

The current issue of "Der Beobachter" takes a deep dive into Swiss watercourses. The comprehensive article presents the severe impairments of our rivers and streams - with a focus on pollution and construction.

The sensors@eawag working group organized the second workshop to foster knowledge exchange around sensors, loggers, wireless communication technologies and  electronics. The goal was to exchange information between the departments and open discussion about current, new or future applications.  20 interested scientists and technicians attended the meeting initiated by Bernhard Wehrli, which was held in Kastanienbaum for the first time.

Switzerland’s surface waters contain vast amounts of thermal energy which could be used for heating or cooling. Based on numerous studies, Eawag scientists have now estimated the ecological impacts of thermal use. 

Periodic oscillations of bottom-water oxygen concentrations can alter benthic communities and carbon storage for decades, reveals a new study published in Science Advances. This is particularly relevant as low oxygen conditions are on the rise in the world’s oceans.

The medal, honouring Kirsten Oswald's excellent doctoral dissertation, has been presented at the graduation ceremony on January 20, 2017.