TRAVERSE CITY, Mich. (AP) - Abundant rain and snowfall have given the Great Lakes a boost this year, but it's too early to declare an end to slumping water levels that have plagued the inland seas since the late 1990s and made life miserable for cargo shippers and marina operators, federal scientists said Wednesday.
All five of the lakes were significantly higher when measured at the end of October than a year earlier, when much of the nation was mired in drought. Even Lakes Huron and Michigan, which have fared worst during the low-water period and in January hit their lowest level since record keeping began in 1918, have risen nearly a foot since October 2012.
But Huron and Michigan, which scientists consider one lake because they are connected and their water level relative to sea level is identical, still were 17 inches below their long-term average for the month. Lake Superior was slightly below average and Lake Erie was normal. Lake Ontario, the only one with regulated levels, was 1 inch above normal.
The dramatic rebound shows "how extremely wet conditions were last spring," said Keith Kompoltowicz, watershed hydrology chief with the U.S. Army Corps of Engineers district office in Detroit. "The snowmelt, combined with heavy rainfall, allowed levels to rise very quickly."
The Army Corps works with the National Oceanic and Atmospheric Administration and Canada's fisheries and oceans department to measure water levels from gauges and stations around the Great Lakes and to predict future trends.
In a forecast released Wednesday, scientists with the U.S. agencies said all five lakes probably would be below their long-term monthly averages by next April, around the time they begin their seasonal rise as winter snowmelt replenishes them. Huron and Michigan were projected to lag 16 inches below normal, although under a best-case scenario the deficit could be as little as 8 inches.
Superior and Erie are expected to be around 3 inches below normal and Ontario about 6 inches below, although experts said the lakes could wind up higher or lower than projected depending on winter precipitation.
"Will we see another very wet period in 2014?" Kompoltowicz said. "Or will we return to maybe drier conditions? That may mean losing what we've gained."
While Superior could return to normal if winter precipitation is heavy, it would take several more wet years for Huron and Michigan to recover, Kompoltowicz said.
Great Lakes levels fluctuate seasonally and have experienced multi-year ups and downs. They were low in the 1960s, but by the 1980s were so high that Lake Michigan cottages were swept away.
In the late 1990s, they were jolted by a sharp decline that experts said apparently was linked to an El Nino event _ a warming of Pacific Ocean temperatures that can affect weather patterns far away. It apparently caused a rapid acceleration in evaporation from the lakes that has continued since, said Drew Gronewold, a hydrologist with NOAA's Great Lakes Environmental Research Laboratory.
Michigan and Huron have been below their long-term averages for 14 consecutive years, the longest period on record.
It's unclear whether the rampant evaporation is the wave of the future, Gronewold said. But researchers have found that winter ice cover on the lakes is shrinking, while water temperatures are warming _ conditions that would appear to favor continued high rates of water loss to the atmosphere.
This year's improvement has provided at least a temporary boost to shipping companies that have been forced to transport smaller loads of iron ore, coal and other commodities. Many vessels have hauled 5,000 to 6,000 tons more cargo this year than in 2012, said Glen Nekvasil, spokesman for the Lake Carriers Association. But that's still a good 5,000 tons below normal, he said.
His group is lobbying Congress to provide more money for dredging shallow harbors.
Regardless of which direction water levels go, "Mother Nature is not going to solve the dredging crisis," he said.
Follow John Flesher on Twitter at http://twitter.com/JohnFlesher
(Copyright 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)