WAUKEGAN, Illinois (CNN) -- Some consumers could see prices rise as lower water levels in the Great Lakes this summer make some shipping routes more difficult to navigate.
Water levels on Lake Michigan as well as Lake Huron have dropped more than three feet (more than 90 centimeters) in the past three years.
The Waukegan, Illinois, commercial harbor on Lake Michigan is now so shallow that ships that mainly carry home-building materials are forced to come in only half full.
"If they have to bring it in half-empty or half-full -- depending on which way you look at it -- then it costs them more money," said Port of Waukegan manager Mary Walker. "That means the product [price], to you the consumer, is more."
'I ran aground'
Parts of Lake Michigan have become treacherous these days even for recreational boating.
The Port of Waukegan is already dredging to keep its harbor open for recreational boaters.
"I ran aground in some sand out there and got caught and couldn't get forward, backward, couldn't heel the boat," said boat owner Bill Hellquist. "We just stayed there."
"We've had several boats come in that were damaged and actually sunk in the lake due to the low lake levels," said Larry Larsen of Larsen Marine Service.
While Larsen's boatyard in Waukegan is making money fixing those damaged boats, it will cost him $100,000 this year to lower docks and dredge his marina.
Better weather to blame
Experts blame the lower water levels on mild winters and hot summers.
Three straight mild winters have produced little snow, which normally helps to raise water levels in the lakes when it melts. In the summer, evaporation is the problem with warmer temperatures.
While the shrinking lakes have left bigger beaches for sunbathers, geologists are concerned about erosion.
"The lake bed is being down cut as the waves come in and break over the shore," said Charles Shabica, a professor of coastal geology at Northeastern Illinois University in Chicago.
Recent Midwest rains have helped bring lake levels up to only 19 inches (48 centimeters) below normal.
Forecasters predict the departure of the La Nina weather pattern could bring more rain and a snowy winter, which might help boaters and shippers stay afloat on the Great Lakes.
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CNN's Patty Davis looks at the causes and effects of the low water levels in Lakes Michigan and Huron