WASHINGTON — As anyone who lives along the St. Lawrence River knows, changing water levels on Lake Ontario can flood river shorelines or leave them dry.
But would a 20-inch increase in water levels on Lake Huron, hundreds of miles away, make any difference?
An expanded study by the U.S.-Canada International Joint Commission could shed light on what has been called the "great leak on the Great Lakes," or the theory that water levels on the Upper Great Lakes have a bigger impact on Lake Ontario and the St. Lawrence than scientists have thought.
The commission, which oversees policies on the two nations' water boundary, said Tuesday that it will expand a study of Upper Great Lakes water regulation to explore possible impacts throughout the Great Lakes and St. Lawrence system if the IJC tries to raise water levels farther upstream. Water levels in the upper lakes have been at historically low levels.
The impact is "believed to be fairly small, but we don't know," said John Nevin, a spokesman for the IJC's Upper Great Lakes study group. Some of the scenarios raised by the study group could increase water levels by just a few inches or by nearly 20 inches, a level last seen at the turn of the 20th century.
In Northern New York, Save the River, the Clayton environmental group, has been focused on the IJC's study of water level regulations on Lake Ontario and the St. Lawrence. But the discussion about the upper lakes raises interesting questions, said Executive Director Jennifer Caddick. Among those is the theory that dredging on the St. Clair River in Michigan has so eroded the river bottom that water escapes into the lower lakes, as if through a drain.
Scientists say water levels on lakes Huron and Michigan are a foot lower because of dredging of the St. Clair River.
The study group will examine the impact of leaving water levels alone or raising them 3.9 inches, 9.8 inches, 15.7 inches or 19.7 inches, the IJC told the U.S. and Canadian governments in a letter.
The St. Clair runs south from Lake Huron to Lake St. Clair, which then drains into Lake Michigan.
As in Northern New York, water levels are controlled in the Upper Great Lakes by man-made structures such as locks and dams. However, regulators are constantly challenged by varying rainfall and snowmelt, forcing decisions that weigh the interests of riverfront property owners, boaters, commercial shipping and environmental protection.
Mr. Nevin said the study of possible effects on the lower lakes and St. Lawrence will be general in scope, rather than a detailed engineering review, and should be completed early next year.