The light snow and minimal ice cover of the three mild winters of 1997-98 through 1999-2000 minimized the need for Great Lakes icebreaking this spring. That was the good news.

But they also had a nasty bad-news boomerang effect. The lack of ice cover promoted more evaporation than normal. The spring runoff did little to counter the effects of evaporation. And both of those factors — combined with less rain in spring, summer and fall months — led to rapidly falling water levels in the Great Lakes.

In a story in the Washington Post in April, Roger Gauthier, supervising hydrologist at the U.S. Army Corps of Engineers office in Detroit, said, “All of this has thrown a whammy at the system at large. It could be the most radical three-year decline ever.”

Since the summer of 1997, the water levels on lakes Michigan, Huron and Erie have fallen 3.5 feet and are receding at a pace that could soon hit all-time lows. Lake Superior is down about 8 inches. (The level of Lake Ontario, which is controlled by mechanical gates, has stayed the same or risen by as much as 4 inches.)

Low water levels, in turn, have led to problems for carriers, forcing many ships to lighten their loads to avoid running aground in suddenly shallower waters.

Lighter loads mean less efficiency and, bottom line, the transport of less cargo. “Even though the demand for iron ore is strong, and the demand for low-sulfur, environmentally friendly coal from out West is booming,” said Davis Helberg, executive director of the Duluth Seaway Port Authority, it seems inevitable at this point that we’ll fall short of 1999 tonnage figures.

“Weather permitting, we expect fewer laker layups in December and more traffic than usual in January. Nonetheless, we can move only so much cargo in our defined shipping season.”

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In its Great Lakes Update newsletters of November 1999 and April 2000, the Corps of Engineers published Q&A sections on water levels. Some excerpts:

Why are water levels so low?
Great Lakes levels are affected by natural and man-made factors. The largest are evaporation and precipitation. Water levels were generally within inches of record high levels during 1997, following two years of above-normal rain and snowfall, especially on the Lake Superior basin. Since the headwaters of the Great Lakes have seen below average precipitation over the past 30 months, the lower lakes have also responded by falling rapidly.

Lakes Michigan-Huron have experienced their most dramatic year-to-year fall on record. Lakes St. Clair and Erie experienced their second-largest year-to-year fall.

This autumn [of 1999], water level declines are also occurring at a faster than average rate. The net result is a greater than anticipated seasonal decline in the levels of the lower Great Lakes.

This fall has continued over the last year [ending April 2000]. The year 2000 continues to show the decline of water levels, with a threat of levels approaching record lows for lakes Michigan-Huron later this year.

What role does evaporation play?
Evaporation for the most part is an invisible but very significant factor in the loss of water from the Great Lakes. During prime evaporation periods, the Lakes may lose 1 to 2 inches of surface water per week to evaporation.

Because of minimal ice coverage and higher than normal air temperatures over the past three winters, evaporation during winter months has greatly increased and has contributed directly to lower lake levels.

How low have the Great Lakes fallen, and how do they compare with all-time records?
Lake Superior fell 2.2 feet from July 1997 to March 1999. Michigan-Huron plummeted nearly 3 feet from July 1997 to September 1999. As of April 1, 2000, Lake Superior was 15 inches above its record low (1926), Michigan-Huron was 10 inches above its record (1964) and Erie was 20 inches above its record (1934). Lake Ontario, meanwhile, was only two inches below average and two feet above its record low (1935).

When was the last time the Great Lakes were this low?
Lake Superior has been nearly constant since July 1999, at 4 to 6 inches less than the long-term average. However, lakes Michigan-Huron, St. Clair and Erie have not been this low since 1966. Lake Ontario was last at its current level in 1991.

Can extreme low water levels be prevented?
Humans have limited control over this massive fresh water system and no control over Mother Nature. If a drought occurs, levels will fall and humans can do little, if anything, to alleviate the condition.

Ship owners this season will be watching the skies, hoping for precipitation and watching the waters while operating with utmost care.