Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Aquifers suffocate when river beds silt up

03.12.2013
In the course of the last few decades, the oxygen concentration levels in aquifers in the Swiss Plateau have dropped irregularly.

Results of the National Research Programme "Sustainable Water Management” (NRP 61) suggest that the irregular decrease might be related to various degrees of silting in watercourses.

A significant proportion of the water we use comes from aquifers that are fed by infiltration along watercourses. River water temperatures have been rising regularly for several decades. By analysing data from municipal pumping stations, the Eawag researchers Simon Figura, David Livingstone and Rolf Kipfer have observed that this trend also extends to groundwater, where the average temperature increase is 0.3 to 0.6°C every ten years.

Sawtooth decrease
The increase in groundwater temperature is probably having a negative impact on the concentration of dissolved oxygen in ground water by encouraging biological activity and therefore oxygen consumption. At the same time, it is reducing the solubility of the oxygen in the water.

A new analysis by the researchers now confirms that there is a trend towards lower levels of dissolved oxygen. As opposed to water temperatures, this decrease is not continuous but follows a sawtooth pattern: it is regularly interrupted by sudden increases that cannot be solely due to temperature.

By analysing the variations in water flow rate and the pumping volumes, the researchers have developed a new hypothesis: high river discharge and high pumping volumes lead to better river bed infiltration. This, in turn, leads to a swift increase in the oxygen concentration. However, it seems that this only happens after extreme spates that sweep away the silt on river beds. The spates thus clean the natural filter formed by river beds, which facilitates greater renewed infiltration and reoxygenation of the groundwater.

This hypothesis on the effects of the removal of riverbed silting is supported by field observations. During the 1970s, a layer of zebra mussels approximately five centimetres thick formed on the bed of the Rhine near to one of the pumping stations studied by the researchers. Several years later, divers noticed that the layer was no longer there. For this period, measurements indicate a clear increase in dissolved oxygen concentrations in aquifers.

What does the future hold?
Climate forecasts for the 21st century predict an increase in extreme weather. Scorching summers such as that experienced in 2003 are likely to become more frequent. Some aquifers became anoxic in 2003. One of the major consequences of this was the solubilisation of iron and manganese particles, which precipitated out of the water in pumping stations, where they negatively affected the operation of the pumping wells. However, there should also be more spates to clean river beds and encourage groundwater oxygenation. The researchers thus expect the slow decline in oxygen levels to continue, but believe that the spates as well as high discharge and high pumping volumes will prevent continuous aquifer anoxia.
(*) Simon Figura, David Livingstone, and Rolf Kipfer (2013). Competing controls on groundwater oxygen concentrations revealed in multidecadal time-series from riverbank filtration sites. Water Resources Re-search. DOI: 10.1002/2013WR013750

(Available to journalists in PDF format from the SNSF: com@snf.ch)

Contact
Simon Figura
Eawag
Überlandstrasse 133
CH-8600 Dübendorf
Tel.: +41 58 765 55 10
E-mail: simon.figura@eawag.ch
National Research Programme "Sustainable Water Management" (NRP 61)
The National Research Programme “Sustainable Water Management” (NRP 61) develops scientific principles and methods for the sustainable management of water resources, which are under increasing pressure. NRP 61 explores the effects of climate and social changes on these resources and identifies the risks and future conflicts associated with their use. NRP 61 operates with CHF 12 million for a research duration of four years. Website of NRP 61 "Sustainable Water Management": www.nrp61.ch

Weitere Informationen:

http://www.snf.ch/E/media/pressreleases/Pages/2013.aspx
http://www.nrp61.ch

Medien - Abteilung Kommunikation | idw
Further information:
http://www.snf.ch
http://www.nrp61.ch

More articles from Earth Sciences:

nachricht From volcano's slope, NASA instrument looks sky high and to the future
27.04.2017 | NASA/Goddard Space Flight Center

nachricht Penn researchers quantify the changes that lightning inspires in rock
27.04.2017 | University of Pennsylvania

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Bare bones: Making bones transparent

27.04.2017 | Life Sciences

Study offers new theoretical approach to describing non-equilibrium phase transitions

27.04.2017 | Physics and Astronomy

From volcano's slope, NASA instrument looks sky high and to the future

27.04.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>