Government forecasters are projecting that
Lake Superior, the largest of the five, will
fall to its lowest level for September since
modern recordkeeping began nearly a century
ago. The amount flowing out of the lake at its
outlet, the St. Mary's River, has plunged too,
and would have to rise by a staggering 50 per
cent to reach the average of the past century.
Levels on Lakes Michigan and Huron are also
sagging, Ontario is down, as is Erie –
although the latter, the smallest by volume,
has been the least affected.
What's going on? While there is no
scientific certainty about what's ailing the
Great Lakes – which together form the world's
largest interconnected body of fresh water –
some fear global warming is at work, causing
them to shrink.
For Michigan and Huron, there is an added
concern: Human meddling may have made them
spring what amounts to a giant leak.
Environmentalists contend that decades-ago
dredging near Sarnia is causing them to lose
an enormous amount of water – estimated at
about an extra 10 billion litres a day, or
enough to fill 4,000 Olympic-size pools.
The falling water levels aren't news to
Gary Vent, whose home overlooks Georgian Bay,
an arm of Lake Huron, near Waubaushene, Ont.
He can see the effects: The shoreline that
used to be 50 metres from his house is now
more than 150 metres. Newly emerging land from
the drying lakebed means that, where he docked
his boat just six years ago, he now plays
"You can hit a solid seven iron," he says.
"I've got a golf course now instead of a place
to park my boat."
Water levels on the Great Lakes go through
seasonal fluctuations driven by the flow and
ebb of the spring snow melt. They also
experience lengthy – perhaps as long as 30
years – alternating cycles of high and low
readings that occur for unknown reasons and
can cause levels to vary by a metre or even
more over the years.
The lakes contain about one-fifth of all
the fresh water on the planet. Although a drop
of a metre may not seem like much compared to
what they contain, about 99 per cent of the
lake water is considered a legacy of the last
ice age and is basically non-renewable.
Only about 1 per cent is replenished each
year through precipitation, and has to offset
what flows out of the lakes through the St.
Lawrence River into the Atlantic Ocean. And
while the lakes are big, they're not
limitless. Except for Superior, their average
depth is less than 100 metres (compared to
oceans that plunge more than 3,000 metres.)
The lakes are now in the midst of one of
their periodic down cycles. But this one seems
much more extreme than usual, lasting for
nearly a decade – prompting questions about
Computer model projections generally show
that the lakes will shrink as climate changes
cause air temperatures around them to rise.
Not only will the lakes themselves become
warmer, leading them to lose more water to
evaporation, but the land is likely to become
drier, reducing the supply of groundwater to
streams that feed the lakes.
At this point, global warming is
speculation, but Mary Muter thinks she has
another explanation for why things are worse
this time, at least for Lakes Michigan and
Huron, which are joined at their northern tips
and consequently have the same water level.
Ms. Muter, head of the environment
committee for the Georgian Bay Association, is
advancing a controversial theory that the two
lakes are inadvertently being drained because
of the effects of dredging on the St. Clair
River in the early 1960s.
She believes dredging has made the river
bed more susceptible to erosion, which over
time has deepened it, and caused more water to
flow into Lake Erie. "The drain hole is
getting bigger," she says.
In 2005, the group commissioned a study
that estimated the erosion had caused an extra
daily outflow of about 3.2 billion litres. An
update issued last month, using more recent
estimates on lake levels, upped the figure to
10 billion litres, leading to concerns that
the ecological integrity of the lakes was
being damaged. Since 1970, the extra drainage
has lowered the levels of the lakes by an
estimated 60 centimetres, the group says.
The International Joint Commission, the
organization that oversees the lakes for the
Canadian and U.S. governments, has announced
that it will study water levels on Lakes
Superior, Michigan and Huron, but it isn't
expected to report its findings on the giant
leak for another three years.
Ms. Muter says the problem could easily be
fixed by piling large boulders into vulnerable
parts of the riverbed to shore it up,
something she says should be done right away,
given that most of the water draining away is
a non-renewable resource.
"I consider it bordering on immoral to not
address this," she says. "How much longer are
we going to wait to do the right thing?"
Environment Canada wants to see what the
IJC concludes before considering mitigation
measures. "We'll be looking to see what they
find out in their study to see if [riverbed
erosion] is a primary factor or whether it's a
secondary factor or no factor in the change in
levels that's occurring," says Ralph Moulton,
a senior engineer at Environment Canada.
Lake Superior is also undergoing travails.
It's experienced below-average water levels
for nearly 10 years, the longest period of
below-average readings on record. Mr. Moulton
says the lake is "almost certainly" going to
set a new record for the lowest September,
eclipsing the previous low-water mark set in
1926, probably by a few centimetres.
Lake Superior levels are being driven down
in part by a lack of rain in the area it
drains. Last year, precipitation was at its
lowest since the mid-1920s.
But another worrisome development is that
Superior has been getting warmer, a reflection
of higher air temperatures around the lake.
According to a study by University of
Minnesota researchers released this year,
summer water temperatures rose about 2.5
degrees from 1979 to 2006.
There is no mistaking the warming – the
lake has less ice cover in winter. And with
Superior not freezing over as much, more of
its water is being lost to evaporation.
Meanwhile, Lake Ontario is about a fifth of
a metre below its average level, and Lake Erie
is down by a little more than a tenth of a
Mr. Moulton says Environment Canada
modelling indicates that under all the
scenarios used, global warming will cause
water levels to drop, possibly by as much as
1.2 metres by 2050, although he also says
these simulations show precipitation will
rise, which hasn't occurred.
Whether global warming is beginning to dry
out the lakes, he says, "is the $64,000