Great Lakes levels have been significantly lower than average for months now, and much of the blame for the record or near-record lows was seen in last year’s extensive drought. However, other possible causes for the continued low levels of the lakes are being investigated, including dredging and river bed mining.

From The Grand Haven Tribune

“Findings recently released by the Georgian Bay Association indicate the decline in levels in Lakes Michigan and Huron is tied to American and Canadian navigational channel dredging, river bed mining and shoreline alteration projects near Port Huron and Sarnia, Ontario.

The association’s report says more than 2 billion gallons of water a day flows out of the St. Clair River — or more than 3,000 Olympic-size swimming pools. All of this water eventually ends up flowing over Niagara Falls and out to the Atlantic Ocean.”
The article, linked above, goes on to discuss the struggle to find a middle ground between navigational needs and maintaining lake levels.