Extended dry spell reflected in lake
By Jack Storey
The Soo Evening News
Published June 2005
UPPER GREAT LAKES - A rainfall deficit of roughly six
inches across northern Michigan and the Eastern Upper
Peninsula so far in 2005 is slowly finding a reflection
in Upper Great Lakes water levels.
A run of late-spring thunderstorms may bring rainfall
closer to the historic average but a Corps of Engineers
official last week said hydrologists have already dialed
back their forecasts for a recovery in lake levels.
Carl Woodruff, hydrologist with the Corps' Detroit District,
said late last week that forecasters have shaved two to
three inches from summer lake level peaks because of continuing
He said even heavy rains through the spring and summer
may have little effect on Upper Great Lakes water levels,
mainly because the ground is so dry. He said dry soils
tend to soak up even copious amounts of rainfall, sending
relatively little downstream to the Lakes.
At the start of June, monthly comparisons of Great Lakes
water levels were beginning to reflect several months
of lighter than normal rainfall. As of June 1, Lake Superior
stood at three inches below its long-term average and
just an inch higher than the same time last June.
The early-June level on Lake Superior showed a slowing
in the Big Lake's gradual rise from near-record lows in
2001. The slowing rise came despite a relatively wet May
around the Lake Superior watershed, during which rainfall
was 120 percent of the average, Woodruff said.
He accounted for the apparent disparity between higher
rainfall and lower overall water supply to the Big Lake
with the dry soil observation.
To the south, Lake Huron and Lake Michigan had no disparity
last month. The watershed feeding the two lakes received
less than half its average May rainfall as near-drought
conditions continue throughout the two lakes' watershed.
At the start of June, the Corps reported Lakes Michigan
and Huron were running about 13 inches below their long-term
average after gaining on the norm through several months
late in 2004 and early 2005. The two lakes rose just one
inch in May compared to an average May rise of three inches.
While lake levels are beginning to reflect rainfall or
lack of it, Woodruff said experts do not expect the lakes
to bottom out if rainfall does not improve. He said hydrologists
recently adjusted the normal summer peak in Michigan-Huron
water levels about two inches lower than forecast in April.
The two lakes usually reach their highest levels of the
year in early July.
"We don't expect a severe drought, but you never
know," Woodruff said of the forecaster's conundrum.
Though Lake Huron and Michigan have fallen roughly half-way
to their recent low point - 23-24 inches below their long-term
average - Woodruff said officials do not expect a repeat
even if the light rainfall pattern persists through early
A similar prospect appears for Lake Superior, which usually
peaks in August or September.
Woodruff said if dry conditions continue to prevail across
the Upper Lakes region, runoff water supply will be negligible
and the only replenishment the lakes can expect from rain
is from precipitation on the lakes themselves.
With thunderstorm potential in the weather forecast for
several days this week, the rains have some considerable
ground to make up throughout the region. Year-to-date
deficits prevail across the north, even though respective
Great Lakes watersheds are much larger.
A report early last week showed Sault Ste. Marie and
Traverse City running very nearly six inches below average
for the year and several other locations across northern
lower Michigan in excess of five inches beneath their
averages for the time of year.
Whatever may be in the precipitation cards for the balance
of the summer, Woodruff said a collapse of water levels
to those seen in 2001 and 2002 is not likely in 2005.
Compared to datum, or the low-water minimum for shipping
channels across the Great Lakes, Lake Superior was still
five inches above the chart minimum in May and Lakes Michigan-Huron
were eight inches above datum.
At the height of the early-century water level drop,
lake levels on all three of the Upper Lakes fell below
datum for months at a time. As recently as February and
March 2004, the Upper Lakes slipped below datum again,
only to recover by some 12 inches later.
Summarizing the Corps' expectations for the balance of
summer on the Upper Lakes, Woodruff said, "Water
levels are a little lower than last year but a lot higher