Low lake levels’ future unknown
Lake Huron’s water levels should rise over the next few months, as they do every spring, but where they’ll be over the long run is open to question.
Great Lakes water levels are rising right now due to snow melt and spring runoff, Drew Gronewald, Great Lakes Environmental Research Laboratory hydrologist, said. Recent rains that have caused flooding in West Michigan should give the lakes an additional boost.
“Michigan is experiencing a very high level of precipitation and runoff,” he said. “This could increase water levels above and beyond of what is an average spring rise.”
However, it’s hard to say whether the spring floods will have an effect beyond this year, or even this spring, Gronewald said.
After dropping about two meters in the late 1990s, water levels in Lakes Michigan and Huron have remained low but stable, Gronewald said. This drop was due to changes in precipitation and evaporation levels.
This period of stability ended in December 2012 and January 2013, when water levels on these two lakes hit all-time lows, Gronewald said. He attributed this to lack of snow pack from the previous winter and significant evaporation over the course of 2012, largely due to higher water temperatures.
Lakes Michigan and Huron are considered to be one lake because they are connected via the Straits of Mackinac, Gronewald said.
The U.S. Army Corps of Engineers’ latest lake levels bulletin shows that Lakes Michigan and Huron have risen from the record lows they hit in December and January, but not by much. They’re still well below average lake levels, and the low water datum level – what’s considered as a reference mark of sorts when measuring water depth.
Lake level changes are due to changes in what Gronewald referred to the Great Lakes’ water budget. That’s water coming into and going out of the Great Lakes basin. Of the many factors in the water budget, evaporation from the lakes, runoff from the land and over-lake precipitation are the three biggest factors.
Low lake levels have an effect on shipping and recreational boating, Tom Landon, National Weather Service water levels expert, said. Lower water levels in the connecting channels between the lakes will decrease the amount of tonnage freighters and tankers can move.
“In terms of recreational boating, there are many harbors right now where boaters can’t even get out of the harbor,” he said.
Water levels also can affect the ecosystem along the shoreline, Landon said. As the lakes recede, plant life along the shoreline changes, and aquatic communities can shrink.
There’s considerable uncertainty as to what lake levels will do over the long term, Gronewald said. He referred to several models, some of which show the lakes returning to average levels or higher. Others show them going even lower than they are today.
This uncertainty is “a direct representation of the uncertainty of the future climate,” Gronewald said, adding it’s unknown how much climate change will affect lake levels.
The Great Lakes have the longest continuous coastline in the lower 48 states, Gronewald said. There are 4,530 miles of coastline, compared to 2,170 on the Atlantic Ocean, 1,630 on the Gulf of Mexico and 1,300 on the Pacific. Alaska and Hawaii have the Great Lakes beat, with a combined 6,330 miles of coastline.
Unfrozen fresh water also is in no short supply throughout the Great Lakes, with Lakes Michigan and Huron being the largest in the world in terms of surface area, and Lake Superior coming in second, Gronewald said. Lake Erie comes in at ninth and Lake Ontario at 11th.