Tuesday, June 19, 2007

Great Lakes--Lower Levels Raising Concern

Visible by satellite--the earth's largest figure-ground study--the Great Lakes give shape to Michigan. The Great Lakes State is surrounded by 20% of the world's fresh surface water (source). Alaska is the only state with more coastline (we have 3,288 miles of it).

At the moment, a lot of people are worried about low lake levels and with reason. Lake Superior is at its lowest level since the Dust Bowl years. The Duluth News Tribune reports that for the first time in more than 30 years the 71-foot ship Winonah will not operate from Grand Portage to Isle Royale.

Sootoday.com reported a contentious public forum held on the Canadian side of the Soo last Thursday. It quotes Tom McAuley, engineering adviser to the IJC (International Joint Commission) and David Fay, Ontario manager of the Great Lakes St. Lawrence River Regulation Office for Environment Canada's Meteorological Services of Canada:

"For the past nine years, Lake Superior net basin supplies have been at a net loss," said Fay. "This means that more water is leaving the lake than is going in."

"It's climate change," he said. "Lake Superior is a very large lake and it hasn't frozen over in years."

McAuley and Fay agreed that more water is evaporating from the lake between the months of September and February in recent times than ever before in recorded history.

"The lowest level in the lake was in 1926 and we are just one centimeter above that right now," said weatherman Fay. "I expect it will drop below that by September this year."

Fay said he's seen credible models that predict catastrophic water loss in the lake over the next few years as well.


Cynthia Sellinger, hydrologist and Deputy Director at NOAA's Great Lakes Environmental Research Lab in Ann Arbor says,"The western end of Lake Superior has been in a severe drought since last June. Since 2003 parts of Minnesota, Wisconsin and Michigan have been in and out of conditions ranging from moderately dry to severe drought. Lake Superior supplies about 30% of the water to Lakes Michigan and Huron." Less water in Superior means less water flowing into Michigan and Huron. Lakes Erie and Ontario, currently higher than their longterm mean levels,"have gotten a lot of moisture from the Gulf of Mexico,"Sellinger said.

"The upper lakes get a much of their moisture from polar air masses and from the Pacific as well. But recently there has been less of that moisture than in previous years."

Travis Dahl, Chief, Water Hydrology Branch, U.S. Army Corps of Engineers Detroit Office said,"Since 1918, the record lows for Superior were set during the Dust Bowl, but the record lows for Lakes Michigan and Huron actually were set in the mid 1960s." A multi-continent severe drought was to blame.

I was looking for a comforting longterm perspective on the matter of lake levels. After all, a certain amount of fluctuation is normal and has been observed since records have been kept. The hydrologic cycle is a complex interplay of precipitation, evaporation, transpiration, percolation, runoff and outflows.

When asked point blank if there was anything she could say to assuage fears about the impact of falling lake levels, Sellinger said,"not really." Ouch.

"We've had a lot less moisture and more evaporation in the upper lakes. But the lower lakes have been receiving more precipitation from the Atlantic hurricane tracks. So you're getting a mixture of things affecting the region,"she said.

"Increased hurricane activity resulting from climate change will likely bring more moisture into the region of the lower lakes. You can't say that overall that global warming is going to suck the lakes dry, but they do respond to climatic events,"she said. Such events include the year-long severe drought affecting Superior right now, previous multi-continent severe droughts and ongoing events like increasing global air temperatures and ocean temperatures. (The Aral Sea disaster was brought on by human activities, namely massive river diversions.)

What does this mean for human activities? Shipping is already affected. As reported in yesterday's Lansing State Journal, Saginaw River traffic has slowed in part due to water levels. The Toronto Star reported last week, " Windsor harbour master Bill Marshall says low water levels mean ships are forced to carry lighter loads, which in the end means higher prices for consumers." As for recreation, some boaters will not be able to launch from their home docks or marinas (source).

A multitude of government agencies--Canadian, U.S. and bi-national--collaborate to monitor and steward the Great Lakes. The lakes have always commanded our respect and humility. As vast as the lakes are, global changes will have an impact.

From the Great Lakes Atlas published by the U.S. EPA, Great Lakes National Program Office:

"Warmer climates mean increased evaporation from the lake surfaces and evapotranspiration from the land surface of the basin. This in turn will augment the percentage of precipitation that is returned to the atmosphere. Studies have shown that the resulting net basin supply, the amount of water contributed by each lake basin to the overall hydrologic system, will be decreased by 23 to 50 percent. The resulting decreases in average lake levels will be from half a metre to two metres, depending on the GCM [general circulation model] used."

Walk lightly, everyone.

(Since this was posted the Independent (UK) has published Climate change blamed as Superior shrinks, June 20, 2007)