Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

'Thermal pollution' in rivers not fully mediated by gravel augmentation

09.06.2011
Cool patches created by adding gravel, however, can serve as important refuges for fish

Although adding gravel to a river to replace lost sediments won't likely cool the whole river channel, it can create cool water refuges that protect fish from thermal pollution, according to a U.S. Forest Service Pacific Northwest Research Station study.

The research—featured in the June 2011 issue of Science Findings, a monthly publication of the station—is among the first to explore the interplay between sub-surface water flow and temperature in large rivers and is helping to guide river restoration strategies in the Pacific Northwest.

In the study, which began in 2006, station research hydrologist Gordon Grant and Oregon State University colleagues Barbara Burkholder and Roy Haggerty examined the effect of subsurface water flow through riverbed sediment—a process known as "hyporheic flow"—on daily minimum and maximum water temperatures. The focus of their study was Oregon's Clackamas River, which, at the time, was undergoing intensive restoration planning efforts led by Portland General Electric (PGE) as part of the relicensing process for the river's hydroelectric system. The addition of gravel to the large river as part of these efforts—aimed primarily at reversing changes in river channel morphology that have resulted from sediment transport being interrupted by the dams—allowed the researchers to explore whether doing so had any measurable effect on reducing "thermal pollution," or unusually high water temperatures caused by human activities like dam operation, logging, and wastewater treatment.

"Previous work suggested that water emerging from gravel bars might actually be cooler than the surrounding water," said Grant.

The research team hypothesized that the continual cycling of subsurface water through the riverbed—during which cool nighttime water would travel through the gravel bar, exiting and mixing with the stream during the warmer daytime—would have a "buffering" effect that would keep the river's daily peak temperatures down, but not necessarily change the river's overall mean temperature. To explore their hypothesis, they mapped the locations of gravel bars along a 15-mile stretch of the river and documented the temperature of water cycling into and out of each of them.

They found 52 temperature differences within the stretch of the Clackamas, with temperatures at these locations from 1 to 4 degrees cooler than the main channel. The researchers were then able to link the cooler areas with specific gravel bar features and with specific times and locations within the Clackamas to create models that depicted the subsurface flow patterns—ultimately revealing that a very small percentage of the river's water actually passed through the gravel bars, making any overall effect on the mean temperature minute.

"Results showed a hundredth of a degree of temperature change through a single bar," said Grant. "Not much."

This finding suggests that gravel augmentation alone is not likely to have a significant temperature-mediating effect in large rivers. However, the work demonstrated that gravel augmentation may provide local habitat benefits to fish and small invertebrates by creating cool areas within rivers where they can seek refuge during hot weather.

To read the June 2011 issue of Science Findings online, visit http://www.treesearch.fs.fed.us/pubs/37952.

The PNW Research Station is headquartered in Portland, Oregon. It has 11 laboratories and centers located in Alaska, Oregon, and Washington and about 425 employees.

Yasmeen Sands | EurekAlert!
Further information:
http://www.fs.fed.us
http://www.treesearch.fs.fed.us/pubs/37952

More articles from Agricultural and Forestry Science:

nachricht Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University

nachricht New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>