Lake Huron Basin Update - Ontario Side
Water Levels a Concern in Lakes Michigan and Huron
By Mary Muter, Georgian Bay Association
Back in 1999 when water levels began to decline, no one was
surprised as the levels had been well above average for 30 years,
and we all knew that Great Lakes water levels are cyclical. In
others words we expected the decline. But when levels stayed
low for five years and approached record lows, some people
began to ask questions. And in the relatively shallow waters
among the 30,000 islands on Georgian Bay, the impact of
sustained low levels was significant. The main concern was that
the wetlands not only dried up but also began to convert to
grassy meadows. Wetland biologists told us that once that
happened it would take a decade or more for the wetlands to
re-establish if and when the water levels returned to more
normal levels. And even more worrisome was the reality that the
aquatic life forced out of these particular wetlands could not find
similar habitat on the adjacent steep granite shorelines. Since
wetlands are needed by over 70% of Great Lakes fish at some
point in their life cycle for spawning, nursery or feeding habitat,
we knew that this loss of wetlands could further threaten the
already declining Georgian Bay/Lake Huron native fishery.
It was then that the Georgian Bay Association (GBA) began its
own investigation into what might be causing this steep decline
in water levels. It is a very complex topic, for many factors
influence levels; so from our membership we formed a committee
with several engineers reviewing extensive historical data.We
came to the conclusion that, at the place where Lake Huron
drains out, there appeared to be an increase in the conveyance
capacity of the St. Clair River that could be contributing to the
lower lake levels. Then GBA Foundation decided to retain the
internationally respected coastal consulting engineering firm
W.F. Baird and Associates to review our findings. This was a huge
undertaking by a relatively small non-governmental organization
(NGO), and GBA Foundation had certainly not done anything like
it before. Baird then confirmed our findings and added more
shocking ones. The research report is available on our website:
www.georgianbay.ca.
According to the Baird Report, Lakes Michigan and Huron –
considered one body of water because they are connected at
the Straits of Mackinac – have permanently lost an additional
12 inches since 1970 because of ongoing erosion at the mouth of
the St. Clair River. This erosion has gone undetected since the
1962 dredging for navigation.
All told, the dredging and erosion have accounted for a water loss
from the lakes equivalent to 28 Lake St. Clairs or 1/4 of Lake Erie,
according to the Baird Report.
Because the extra water moves so quickly through Lake St. Clair,
the Detroit River, and Lake Erie on its way over Niagara Falls, it has
not raised the levels of those waters appreciably, reported Dr. Rob
Nairn, the principal researcher. A modest resurgence in Great
Lakes water levels during the past two years is part of a natural
cycle, but doesn’t mask the fact that the Huron/Michigan waters
are still a foot below where they would be without the erosion,
Nairn said. During the last half of 2005, the resurgence seems to
have ebbed away. And the problem can’t be explained by natural
forces, said Nairn. Geologists say that erosion in the St. Clair River
basin stopped between 2,000 and 3,000 years ago. But it began
again in the 1900s because of man-made factors including:
- Dredging of the channel to 27 feet deep to
accommodate ships;
- Erosion at the sites of sand and gravel mining that
took place in the river in the early part of the 1900s; and
- Erosion-control structures protecting beaches on lower
Lake Huron that deprive the St. Clair River of sediment that
normally would have washed into it and filled holes in the
river bottom.
The Georgian Bay Association took the Baird Report to the
International Joint Commission (IJC), and we were told that this
level of work by an NGO was unheard of.We are pleased that the
IJC recently announced a revised Upper Lakes Levels Study that
includes best mitigation designs and costs.
Unfortunately we have learned that the IJC had looked at this loss
of Huron/Michigan water on at least three previous occasions.The
last time was in the early 1960’s, when they knew engineers were
again lowering lake levels by dredging for the 27-foot channel. But
at that same time the IJC discovered that Chicago was taking too
much water; so it forced Chicago to cut back. Then water levels
rose, and the interest in mitigation was lost. The problem has now
come back as the ongoing erosion continues to allow more water
out. Recent bathymetry data shared with us by the US Geological
Survey show that additional erosion at the outflow of Lake Huron
took place between 2000 and 2003.
We are hopeful that a solution can finally be put in place. The first
action will be to cover over the eroding areas with hard rock
substrate to stop the erosion of exposed soft clay. This may
actually improve a resurgent sturgeon spawning habitat in the
very deep, fast flowing part of the river, where it is now over 60
feet deep. (Ships need only 30 feet of depth.) And then flexible
control gates such as were designed previously could be put in
place. One thing we know we don’t want, or need is locks. They
would lead to very challenging ecological problems.
Until something is done though, the forecast for future water
levels is not good – especially if climate change is added to the
mix. The other Great Lakes have the capacity to hold back water
under any scenario. Something has to be put in place for Lakes
Michigan and Huron.
For more information:
Georgian Bay Association, Georgian Baykeeper, GBA Foundation
mmuter@sympatico.ca
Disclaimer:
The interpretations and conclusions presented in this newsletter represent the opinions of the individual authors. They in no way represent the views of the Tip of the Mitt Watershed Council, the C.S. Mott Foundation, subscribers, donors, or any organization mentioned in this publication.
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