The U.S. Army Corps of Engineers predicts that both Lake Michigan and Lake Huron will continue to decline, reaching water levels not seen since 1964 at the end of 2012, and set new records for low water levels in early 2013. Connected by the Staits of Mackinac, the lakes are a single body of water from a hydrological perspective.
According to US Army Corps of Engineers Chief of Watershed Hydrology Keith Kompoltowic the low water levels are a result of reduced of runoff from snowmelt followed by a hot, dry summer.
The causes for the declining water levels are open to debate, most likely complex and cyclical. In fact, part of the declining water level is a result of the land rising, through a geological phenomenon knows as isostatic rebound. Land that was once compressed by the weight of glaciers rebounds.
This is the longest period of time — more than a decade — that Lakes Huron-Michigan have remained below their long-term average lows since the Corps began keeping records on Great Lake in 1918.