* Heat, drought, lack of snow drew down water levels
* Water level has been dropping for 10 years
* Level could fall to record low this winter
By Sam Nelson
CHICAGO, Nov 30 (Reuters) - The worst drought in the United States in over a half century slashed crop output, snarled river transportation and is now drawing down water in the U.S. Great Lakes, particularly Lake Michigan.
The low water was exposing broad expanses of shoreline to owners of lakeside property, but so far no significant impact has been reported by commercial shipping interests, the U.S. Army Corps of Engineers said this week.
The water level in Lake Michigan is within two inches of its December record low set 48 years ago. The lake is one of the five lakes that make up the Great Lakes, which cover 94,000 square miles and straddle the United States and Canadian border.
The water level on Lake Michigan may fall to record lows over the winter unless heavy rains fall soon or large snowstorms blanket the area surrounding the Lakes.
"There is a good chance of setting record lows. We've been falling below average for over a decade due to lean winter snowfalls," said Keith Kompoltowicz, chief of watershed hydrology for the Army Corps of Engineers.
The Great Lakes, which comprise lakes Michigan, Huron, Erie, Superior and Ontario, contain about a fifth of the world's fresh water supply and 84 percent of the supply in North America.
Drew Gronewold, research hydrologist with the National Oceanic Atmospheric Administration's (NOAA) Great Lakes environmental research laboratory said water levels have been dropping since the 1990s.
"Water levels naturally fluctuate and have been at low levels for 10 years. But this year of extreme high water temperatures increased evaporation rapidly and that helped draw down water levels," Gronewold said.
Kompoltowicz said the record low water line for Lake Michigan-Lake Huron for December was 576.18 feet set in 1964, January's record low was 576.12 feet in 1965 and February's record low was 576.08 feet in 1964. (Reporting By Sam Nelson; Editing by Bob Burgdorfer)