UW News

August 4, 2005

Of pond critters and river currents

FARM POND FINDS: During the summer, recreational use of the 1 million or so farm ponds in Texas reaches its annual peak. To an angler, that means lots of fishing, but to Billy Higginbotham, Texas Cooperative Extension fisheries and wildlife specialist, it means more stories for his ever-expanding “weird pond problems” file, according to AgNews, a publication of the Texas A&M University System Agriculture Program.

“Farm ponds can be the sources of some pretty weird critter sightings and occurrences — some common throughout the state and a few that rarely happen at all,” Higginbotham told AgNews.

The examples often reflect a bit of detective work. For instance, a woman complained that her sunfish had died for no reason. Not so — an autopsy of the fish revealed it had died from ingesting toxic fire ants that dropped into the water from nearby vegetation.

Then there were the jellyishlike blobs of softball to basketball size, floating free or attached to submerged branches or pilings. “Also called ‘moss animals,’ they are a sign of good water quality and do no harm,” Higginbotham said. Leeches, grub worms and water snakes are present in those ponds, too.

TWO-WAY RIVER?: Since 1900, the common Windy City wisdom has been that engineers had successfully reversed the flow of the Chicago River to keep wastewater from polluting city drinking water and Lake Michigan. In fact, it was hailed as one of the seven engineering wonders in the country.

But in 1998, scientists from the U.S. Geological Survey detected traces of mysterious currents deep in the river that were running toward the lake, not away from it. The water flow is not just an academic question — if water is flowing toward the city and the lake, according to the campus news bureau’s report, it’s most likely coming from the river’s North Branch, which gets much of its flow from a wastewater treatment center, and it could threaten the water quality of Lake Michigan.

As engineers pondered the problem, Marcelo Garcia, a professor of civil engineering at the university, began to suspect the culprit was a density current, or a layer of denser liquid flowing underneath the less-dense river. He got funding to research the idea in 2001, and built a working model of the river as it flows near the city. He has apparently proved his theory of water flow, but says more research is needed on how to prevent such currents in the future.

“What is unbelievable is that everybody had thought for 100 years that the river has flowed away from Lake Michigan, but the river has not lost its memory,” Garcia said. “This shows that if the river had a choice, it would still flow to the lake.”