What is an inch of Lake Superior worth? Consider this: it takes 551 billion gallons of water to raise the level of Lake Superior by one inch.

That much water meets a year’s worth of water use for about 1.1 million Americans or for about 1.7 million Canadians.

That much water allows Lake Superior’s freighters an extra inch of draft (the amount of boat below the surface), which means about 270 extra tons of cargo for a 1,000-foot laker or about 100 extra tons for the largest ocean-going vessels (740 feet) sailing the Great Lakes. An inch of lost clearance can mean a loss of up to $28,000 per load for an ocean-going ship.

Top: Inches can equal thousands - water clearance to dollars - for freight-carrying vessels. Below: A water level chart for Lake Superior shows the ups and downs of the big lake in metres for the last 140 years. The red line is the long-term mean average.

That much water powers the hydroelectric plant at St. Marys River for more than a month of 24-hour, near-peak capacity at 25,000 cubic feet of water per second. (It generally runs 12,000 cfs to 26,000 cfs.

In other words, one inch of Lake Superior - whether calculated in kilowatt hours, shipping dollars or glasses of refreshing, life-giving beverage - is worth quite a lot.

Now consider this: at press time, Lake Superior was 6 inches below its long-term water level average. Luckily, that’s 8 inches higher than the same time last year, reports the U.S. Army Corps of Engineers.

Since 1998, the water levels of the Great Lakes in general, and of Lake Superior in particular, have generated great interest as they’ve inched lower. Most of the lakes hover near 35-year lows; lakes Michigan and Huron came painfully close to all-time recorded lows in the summer of 2000.

From commercial shippers to small boat marinas, from lakeside nuclear power plants to lakeshore property owners, everyone seems to be watching the comings and flowings of Great Lakes water levels.

But those who watch the closest are those who predict for the rest of us whether the waters might rise or recede in the months to come.

A large stable of researchers in a half dozen U.S. or Canadian federal bureaus employ water-watching tools that range from on-the-ground volunteers with measuring instruments to low-flying aircraft capable of measuring the water in snow to statistic-gathering buoys on the lakes or even farther out - out of this world - to a series of satellites that periodically focus on the Great Lakes.

Bringing every scrap of current statistical information to bear on computer models of what should happen, however, is far from a guarantee of what will happen.

“You’re dealing with a vast area with a lot of variability going on,” says Roger L. Gauthier, chief of the Watershed Hydrology Branch of the Great Lakes Hydraulics and Hydrology Office - the Corps’ Detroit District.

“Our institutional approach is that we’ll forecast six months into the future and that’s all we’ll tell you.”

Six months might not tell you much about a Great Lakes trend. Some researchers speculate that the lakes might be on a 30- or even a 160-year cycle of high and low waters, says Cynthia Sellinger, a water level expert with the Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan.

“The lakes have been following global weather patterns,” she says. “They show lows during the Dust Bowl. Lake Superior’s low was in 1926. Its high was in 1985.”

Lakes Michigan and Huron reached their record high water levels in 1986. Before then, their highest recorded levels were in 1886.

So what can be expected of Great Lakes water levels in the next six months?

Look for current signs, researchers suggest.

“The thing that makes the biggest difference in forecasting is knowing the current conditions in the basin,” says Tom Croley with the National Oceanic and Atmospheric Administration’s laboratory in Ann Arbor. “The storage of water, the heat of the lakes, the temperature of the air … any day that we want to make a forecast, we start with these initial conditions.”

For instance, you don’t need high-tech equipment to read “snow shortage” from the high number of ski marathons, dog sled races or snowmobile rallies that have been delayed, cancelled or shortened all around Lake Superior this winter.

“The intriguing part is that Lake Superior is normally the most stable of all,” Roger says. “It has the least amount of variance. It is consistently closer to average in terms of the timing of the snow, normally starting in November and lasting into May with peak accumulations sometime around the 10th of March.”

Snow is not the only winter indicator of future water levels in a Great Lake.

Lake Superior’s vast surface area (31,700 square miles) and vast water volume (3 quadrillion gallons) make it a prime candidate for winter-time evaporation. The water absorbs heat in the summer and retains it in the winter. When the lake remains ice-free most of the winter - as Lake Superior did this winter - nothing blocks the warmer water from the colder air and evaporation sucks water away. Not quite half of the water lost from Lake Superior each year leaves via evaporation. The remainder flows out through the St. Marys River.

“We were hoping to get a nice ice cover. It seems the time is passing for that,” Cynthia Sellinger says.

“We have evaporation on the lakes (this winter),” Tom Croley says, “which is very much a function of the heat on the lake as well as wind speeds. With heat in the lake, we have a much higher evaporation rate. Lake Superior is a very deep lake and it has a huge heat capacity.”

“If what we’re seeing now continues, this could be as bad as last year for low water levels,” Roger says.

“We expect levels to remain below average over the next six months for Lake Superior,” echoes David Fay, senior water resources engineer for Environment Canada.

How Lake Superior is faring concerns those throughout the Great Lakes. After all, 25 percent of the water added each year to lakes Huron and Michigan comes from Lake Superior through the St. Marys River.

“Superior being the headwaters, if the water level on Lake Superior gets above average, that bodes well for the rest of the system,” Roger Gauthier says.

One thing might help to raise water levels of the Great Lakes and the hopes of the shipping industry, marinas and power plants: Early spring snows or late spring showers.

Great Lakes water levels are represented in feet above sea level. The water level chart that appears in each issue of this magazine is taken from the U.S. Army Corps of Engineers and NOAA. It compares the all-time highs and lows as well as the long-term averages and current water level conditions. Daily, weekly and monthly updates can be found on the Corps’ water levels home Website at huron.lre.usace.army.mil/levels/hmpglv.html

“The last thing that we can depend on is to have a good snow pack so that we’ll have a good spring runoff,” Cynthia says.

In 2001, spring runoff accounted for a record high April rise in water levels for Lake Superior. Many believed it signaled an end to the “la Niña” dry effect in place since 1998.

“April happened and we had record rainfall on the Lake Superior basin,” Roger says. “The lake went up 11 inches in one month. That was quick relief, but since that time, supplies have been back to getting below average.”

For now, most U.S. and Canadian researchers are expecting more of the same when it comes to low water levels in the Great Lakes for the next six months. And while a 12-month forecast does circulate even through the NOAA environmental laboratory in Ann Arbor, Tom Croley admits, “after six months, I just ignore that.”

So for Lake Superior shoreline property owners, this could be another year without loss of beachfront.

For small boat marinas, this may be another year of needing to dredge to keep slips accessible.

For Edison Sault Electric, which provides hydroelectric power from the St. Marys River to the eastern half of Michigan’s Upper Peninsula, this could be another year of logging extra costs when it must occasionally use its diesel-run units or buy power from other sources.

For Great Lakes shippers, it may be another year of more frequent trips with lighter loads but heavier costs.

For everyone, it will be another year of careful watching to see what will happen with Great Lakes water levels and to wonder through the summer whether Lake Superior will be inching up or inching down.

Lake-effect snow, like that seen in this 2000 satellite image, can be dry as far as snows go. “It’s the process by which the snow forms,” explains Thomas Carroll, National Operational Hydrologic Remote Sensing Center. Lake-effect snows tend to contain comparatively little water because the snow forms in a relatively shallow atmospheric layer where warm, moist air over the lake mixes with cooler from-the-land air. The deeper that “mixing” layer, the more moisture absorbed by snow as it forms. “It is difficult to get dense, wet snow if the atmospheric mixing layer is less than 1 to 1.5 kilometers,” says Tom. Plus, most of the moisture came from the lake itself.

As a general rule of thumb, Tom says, 10 inches of “normal” snow generates one inch of water. But the 81.5 inches of lake-effect snow dumped on Buffalo, New York, early this winter had low water content. “It would take 20 inches or more of snow, of that lake-effect, Buffalo-type snow, to make 1 inch of water.”

 

MINNESOTA SEA GRANT

Another “effect” for Lake Superior comes with fall gales. Lake water levels hardly seem low, given these November 27 storm waves at Duluth, Minnesota’s Canal Park (above). The color map (below) by the Great Lakes Environmental Research Laboratory shows how the Great Lakes wave forecast looked for that day.

F.Y.I. The Great Lakes Forecast System can be found at superior.eng.ohio-state.edu/

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