November 2, 2007
Lower Water Levels Not Linked to Erosion
By JOHN FLESHER
TRAVERSE CITY, Mich. - Video images from the St. Clair River bottom show no evidence of erosion causing water levels on Lakes Michigan and Huron to drop, scientists working for a U.S.-Canadian advisory group said Thursday.Leaders of the research team said the findings were preliminary, and that it was too early to judge the validity of a Canadian group's contention that erosion on the upper portion of the river is a leading culprit in the two lakes' steady decline since the late 1990s.
But they said the underwater video - taken in September along a roughly 30-mile stretch - showed the riverbed is covered with gravel, pebbles and stones up to 10 inches long. The rock layer is stable, meaning "the bed cannot be eroding," the team's report said.
"On a preliminary basis, we're finding that ongoing erosion does not appear to be a cause of low water levels," said John Nevin, spokesman for the International Joint Commission (IJC), which advises the U.S. and Canadian governments on Great Lakes issues.
Researchers acknowledged many questions remained unanswered, such as whether river flow rates have changed over time and how long the riverbed has been stable. The rock layer holding it steady may have been covered previously by sediment that washed away, said Ted Yuzyk, co-chairman of the study team.
Additional measurements will be taken to provide further information, he said.
The video was taken by Bommanna Krishnappan, a research scientist with the National Water Research Institute Ontario, who also reviewed previous reports of sediment flow on the river.
A spokeswoman for the Georgian Bay Association, which blames erosion under the river for the low water levels, said the IJC's report was unconvincing and contained errors.
"It's premature for them to be releasing this information," said Mary Muter, chairwoman of the group's environment committee. "They're wasting time and wasting money."
Low water is causing ecological and economic problems on the Great Lakes, particularly for commercial shippers and recreational marinas.
Lakes Michigan and Huron, which geographically are considered the same lake, are about 20 inches below their historical average levels for this time of year. Lake Superior, meanwhile, hit a record monthly low in September.
Many scientists say the dropoff is caused by drought and milder temperatures, which promote evaporation.
But engineers hired by the Georgian Bay Association, which represents thousands of Lake Huron waterfront property owners, place much of the blame on human activities in the St. Clair River - particularly dredging to deepen the shipping channel during the 1960s.
In an August report, the association said erosion from the dredging is causing Lake Huron to lose an extra 2.5 billion gallons per day. The excess water flows into the lower Great Lakes and eventually the Atlantic Ocean, the group said, likening the widened river channel to an enormous drain hole.
The IJC this year began studying the issue. It initially promised a final report by 2010 but recently said results would be produced a year earlier after getting pressure from U.S. senators and other political leaders.
Gov. Jennifer Granholm and U.S. Sen. Debbie Stabenow last month asked the U.S. Army Corps of Engineers to consider placing underwater barriers in the St. Clair River to limit its flow even before the commission's study is finished.
Editor's note - John Flesher is the AP correspondent in Traverse City and has covered environmental issues since 1992.
On the Net:
Georgian Bay Association: http://www.georgianbay.ca/index.html
International Joint Commission: http://www.ijc.org