Solving the mystery of erosion in the south Tobacco Creek watershed
You may have noticed that after a heavy rainstorm, creeks and rivers often turn the color of chocolate milk. That cloudy brown color is caused by sediments--weathered rock material ranging in size from tiny granules of mud to stones. As it courses along, water sweeps up sediments in the well-known process of erosion. Eventually, the sediments find a home, sometimes in a place where it isn't wanted. And, it's not just mud and sand that gets carried to water sources. Contaminants often catch a ride to waterways by clinging to sediments.
Soil experts David Lobb and Dr. Sheng Li check sediment collection traps. The sediment is collected annually to track the origin and pattern of soil migration.
Photo credit Landice Yestrau
Soil scientist David Lobb investigates the origin of these nomadic sediments. His work is in the Tobacco Creek Watershed, a collection of streams that flow into the Red River and ultimately dump into Lake Winnipeg, Canada. Lake Winnipeg is the final resting place of three major rivers, making it the second largest watershed in Canada. It feels the effects of activity taking place upstream.
"We are all being challenged to look at the watershed as a whole, not just at the water that flows out a watershed," says Lobb.
Watershed health and water quality issues are a growing concern. A variety of human activities can negatively impact watersheds.
Fertilizers used to bolster crop yields, sewage pollution from treatment facilities, and refuse from livestock can leach an excess of nutrients. The nutrients, especially phosphorus, enter large bodies of water like Lake Winnipeg. Algae feeds on this influx of phosphorus and goes into a frenzy of growth, which can lead to the choking out other species and throwing off the function of the entire ecosystem. Sediments are often blamed for carrying this nutrient runoff from topsoil sources like farm fields and livestock production areas.
In the context of these issues, Lobb and his team were keen to examine the sediments traveling downstream toward Lake Winnipeg. In order to better understand where sediments are coming from, Lobb and his colleagues from the University of Manitoba and the University of Northern British Columbia use a technique called color fingerprinting. The color of a particular sediment is key to identifying the specific origin of the erosion. "It's not as particular as fingerprinting in a crime scene investigation," says Lobb, "but we have the tools to get a sophisticated identification of the sources of sediments."
At first glance, the color fingerprinting technique is fairly intuitive. It's also cheap and quick. "In the most simple case, black sediment is from surface sources and light sediment is from subsurface," says Lobb, "That's an oversimplification of a very precise process backed up by statistical models."
The distinction between surface and subsurface sediment sources is important. Subsurface sediment, or subsoil, is usually pulled by the water from the sides or bottoms of streams. Surface sediment, or topsoil, is more than likely coming from farm fields, riparian areas, or forest floors.
South Tobacco Creek revealed some facts that complicate the picture of erosion, and the human role in the process of sedimentation.
"We found that nature is more often to blame for a lot of the sediments we see in our streams," says Lobb, "Humans may not have as much of an effect on the amount of sediment flowing out of a watershed as we've been taught," says Lobb, "but we do have a profound effect on hydrology, and that can contribute to the erosion and sediment produced downstream."
Most of the sediment found in the South Tobacco Creek is from subsurface sources. It's coming from the stream banks and the huge rock walls that borders the creek as it cuts through a 600-foot escarpment. "Most people assumed sedimentation is caused by erosion in farm fields," says Lobb. "But one of the biggest culprits is the natural channel erosion that is constantly taking place."
The color coding technique makes it simple to find the geographic origin of sediment. "What to do with these answers is not as simple," say Lobb, "but precise color fingerprinting allows technology to open up to new directions. We are now looking at managing runoff from farm fields as being as important as managing erosion and sediment losses from farm fields. And, we are looking at managing runoff and erosion from the farm field scale to the watershed scale."
One of the complications is scale. Watersheds are dynamic. The health of one section of stream or river affects another section. To address issues at the watershed level requires looking at the area as a whole. In the case of Lake Winnipeg, the watershed spans an area 40 times the size of the lake itself.
"The public is demanding actions and impacts on a watershed scale," says Lobb. "Therefore, practices and processes have to reflect that larger regional scale."
Read the results of the study in the Journal of Environmental Quality.
Susan Fisk | EurekAlert!
Plasma-zapping process could yield trans fat-free soybean oil product
02.12.2016 | Purdue University
New findings about the deformed wing virus, a major factor in honey bee colony mortality
11.11.2016 | Veterinärmedizinische Universität Wien
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Power and Electrical Engineering
16.01.2017 | Information Technology
16.01.2017 | Power and Electrical Engineering