A new report says that a joint U.S.-Canadian study exploring lower water levels on Lakes Michigan and Huron has significantly underestimated the amount of water the lakes have lost due to erosion on the St. Clair River.

A study released in the spring by the International Joint Commission said the water loss was four inches. But the report prepared by the coastal engineering consultants Baird & Associates says the water loss was actually more than nine inches.

A spokesman for the Joint Commission says the group disagrees with the report. When it released its study in May, the group said there was no need to place barriers in the St. Clair to stem the outflow.

The report's author says he doesn't want a public spat, but is convinced the Joint Commission's study is based on miscalculated data.