May 09, 2014
Research points to river revival
CARBONDALE, Ill. -- All the Lower Cache River needed was a little push.
Cut off for almost 100 years from its headwaters, the river changed from a vibrant fishery into a stagnant, linear swamp over time. Duckweed covers its surface in the summer, preventing photosynthesis in the water. And this, coupled with its zero flow rate at times, gives the stilled waters a near-zero oxygen content. Life within has been all but snuffed out.
But a team of researchers from Southern Illinois University Carbondale has found evidence that restoring even a modest flow to the Lower Cache would reverse decades of decline and could restore the Lower Cache River to its former glory, perhaps opening a floodgate of economic opportunity in the process.
Matt Whiles, professor of zoology and interim director of the Cooperative Wildlife Research Laboratory at SIU, is leading that team. Whiles said preliminary results from a study conducted last summer indicate restoring a low flow rate could result in a 20 to 30 percent increase in the oxygen in the water, making it again habitable for fish and other creatures.
In nature, oxygen can become dissolved in water mainly in two ways: through turbulence, where ambient air is essentially mixed into the water, or through photosynthesis, where plants in the water give off oxygen in the process of making their food.
But cutting off the Lower Cache eliminated turbulence during most of the summer and also allowed duckweed to take a firm hold, both of which killed oxygen levels.
“Having some water flow does several things, including getting rid of the duckweed,” said Whiles, who also heads up the SIU Center for Ecology. “It creates a biologically significant difference in the amount of oxygen in the water.”
The Cache River was cut in half in 1915 by a project known as Post Creek Cutoff. Its purpose was to drain wetlands in the area for agriculture use and timber harvesting.
The Upper Cache River, still connected to its headwaters, maintained flow. That flow, hemmed in to a smaller area by the Post Creek Cutoff, is causing the Upper Cache River to “incise” or cut down into the ground, leaving wetlands nearby high and dry. Meanwhile, the Lower Cache River became an elongated swamp, stagnant and choked by vegetation.
Whiles and his team essentially simulated what would happen if the upper and lower Cache rivers were partially reconnected. They did this by pumping water from nearby Buttonland Swamp into the Lower Cache River, giving the waters a gentle push, with the pumping action re-establishing some minimal flow, allowing the researchers to mimic those conditions and weigh the effects.
The study, when complete will provide important information on the wisdom of a partial reconnection of the river.
The Illinois Department of Natural Resources provides most funding for the reconnection simulation project through a U.S. Fish and Wildlife Service state wildlife grant, along with matching contributions from the Nature Conservancy Illinois and Little River Research and Design in Carbondale. The IDNR, along with Ducks Unlimited, the Natural Resource Conservation Service, The Nature Conservancy, U. S. Fish and Wildlife Service, the Big Creek Drainage Commission, and SIU Carbondale, have all contributed to the project.
The project began three years ago, when the researchers began placing oxygen sensors in the Lower Cache River to measure its oxygen content, providing a baseline for their experiment. Whiles admitted he was surprised at these initial measurements.
“There was no oxygen at times,” he said.
Whiles said the Cache River project has the potential to become a model for other river restoration projects worldwide, and that it is important to do studies such as this before taking action.
“We hope to provide the scientific basis for good decision-making,” Whiles said. “We need to keep perspective and study what the ecological benefits are before we just decide to do something.”
Whiles said the project has provided valuable research opportunities for SIU students such as Sophia Bonjour, a senior in zoology, Karen Bauman, a graduate student in zoology, and Heidi Ranatala, a post-doctoral fellow. Tracy Boutelle Fidler, who heads Shawnee Resource Conservation and Development’s Cache River Project, and Steve Gough, of the Little River Research & Design, also played important roles in the effort, he said.
“This has been a group effort to find these answers,” Whiles said. “We all want to make the best decisions based on good information.”