EPFL's heating a treat for lake trouts

December 5, 2012 by Jan Overney
EPFL's heating a treat for lake trouts
Credit: Andreas/Flickr under a Creative Commons License

A recently conducted study also shows that the streams surrounding EPFL can handle future campus growth.

Since 1985, the EPFL has relied on from to heat and cool their buildings. Once used, this water is injected back into the nearby streams. For his Master's project at the Laboratory, Jonathan Sidler studied the impact of this alternative heating approach on the health of the stream ecosystems, which contribute to the mating grounds of one of the largest trout populations in Western Europe. Surprisingly, he concluded that injecting lake water into the streams improves their overall ecological quality and their attractiveness to the fish.

Influenced by the 1970s , a decision was made in the mid 1980s to heat and cool the buildings of the EFPL campus using water from Lake Geneva. Extracted at depth of 68 meters below the lake's surface at 6°C, this water is warm enough to supply heat in the winter using heat pumps and to absorb excess heat in the summer. As a result, heating has decreased considerably since before the introduction of this approach over 25 years ago - and that despite today's much larger campus.

Sidler's Master's thesis focuses on analyzing the impact of the heating and cooling system on the stream ecosystems and makes predictions on the impact of the campus expansion that is underway. His project was spawned in an attempt to evaluate the water quality of the Sorge, the Mèbre and the Chamberonne that flow near EPFL and UNIL. Water fed back to the streams after passing through the heat pumps, located near the Sorge metro station, was diluting the river water, as well as the that was under examination. Finding a way to account for this dilution opened the door to Sidler's investigations.

Bringing back lake trout

Lake trout, an to Lake Geneva that can weigh well over 15 kilograms, tend to be picky in choosing where they mate: preferably in rivers, where the temperatures are not to warm in the summer, and neither too warm nor too cold in the winter. If the river water falls within this narrow temperature range, the fish find conditions in which they can reproduce and thrive.

While the fish may have been adapted to the river's environment in the past, agricultural practices and urbanization have had an impact on the temperature and flow rates of the streams, making them less attractive to the trout. "By injecting the used lake water back into the streams, we actually cool them in the summertime and early winter, keeping the temperatures within a range that the fish are adapted to. Besides that, we help maintain river flow even in the dry season, and dilute any pollution that is present in the rivers," explains Luca Rossi, who supervised Sidler for his Master's thesis.

What is good for the fish is not necessarily beneficial to other species. The arbitrary changes in flow rate that depend on the heating and cooling needs of the campuses could spell trouble for beaver populations that have settled nearby. But a growing beaver population suggests that the fact that the rivers never run dry outweighs the detrimental effect of fluctuating flow rates.

An outdoor lab surrounding campus

As the campus expands, the demand for lake water will increase, as will the amount of water injected back into the rivers. Using computer simulations, Sidler was able to predict the bounds on the temperatures that the river will be exposed to. Taking into account two major construction projects that are underway, the conference center at EPFL and the Geopolis building at UNIL, both of which will adopt the same approach for heating and cooling, he showed that the rivers could sustain this increase. The Sorge river, however, would be pushed close to its limits, especially in the winter months, when the water used for heating would be injected back into the already cold river.

Besides addressing these pragmatic questions in need of an answer, this project is laying the groundwork to using the Sorge, the Mèbre and the Chamberonne as a lab ecosystem in EPFL's backyard, in the same way that Lake Geneva has been used in the Leman21 and élemo campaigns. "Now that everyone knows that we have a lake, it's about time that we take advantage of our rivers," says Rossi.

Explore further: Climate change has surprising effect on endangered naked carp

Related Stories

Climate change has surprising effect on endangered naked carp

December 19, 2006

Forthcoming in the January/February 2007 issue of Physiological and Biochemical Zoology, a groundbreaking study reveals an unanticipated way freshwater fish may respond to water diversion and climate change. Endangered naked ...

Mini-submarines to gauge Lake Geneva pollution

June 14, 2011

Two mini-submarines that have filmed the wreckage of the doomed luxury cruise liner Titanic will dive into Lake Geneva to gauge its pollution levels, Swiss researchers said Tuesday.

Climate change endangering U.S. salmon

January 7, 2008

Salmon in the Columbia River and other U.S. streams could face an uncertain future if global temperatures continue to warm, experts say.

Recommended for you

Study finds parrotfish are critical to coral reef health

January 23, 2017

An analysis of fossilized parrotfish teeth and sea urchin spines by researchers at Scripps Institution of Oceanography at the University of California San Diego showed that when there are more algae-eating fish on a reef, ...

Caves in central China show history of natural flood patterns

January 19, 2017

Researchers at the University of Minnesota have found that major flooding and large amounts of precipitation occur on 500-year cycles in central China. These findings shed light on the forecasting of future floods and improve ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.