The Great Lakes Are In Trouble
Drought has pushed Lake Superior's water level to its lowest point on record for this time of year. Data shows Superior's average water level in September dipped 1.6 inches beneath the previous low for that month reached in 1926. The U.S. Army Corps of Engineers has the level at 4 inches below the record.
It has been 81 years since the lake has reached a new monthly low. The Corps recorded Superior as also setting a record by a half-inch in August. But the NOAA lab had the lake above its record level then. The lake has now dipped beneath its long-term average level for a decade.
All the Great Lakes, which make up about 20 percent of the world's fresh surface water, have been in decline since the late 1990s. Lakes Huron and Michigan are about 2 feet below their long-term average levels, while Lake Superior is about 20 inches off. Lake Ontario is about 7 inches below its long-term average and Lake Erie is a few inches down.
Levels for the lakes fluctuate throughout the year. Superior, which feeds the other lakes, rises in spring and summer as melted snow flows into its headwaters, then recedes in fall and winter. But precipitation is well below normal in the Lake Superior watershed, and unusually mild winters have reduced the winter ice cap, boosting evaporation. Possible causes for the low water include historical cycles, weather patterns and global warming.
October 2, 2007 6:43 AM | Category: Great Lakes, Lake Erie, Lake Huron, Lake Michigan, Lake Ontario, Lake Superior