Annual Fluctuations

   The level of Lake Erie, as with the levels of all the other Great Lakes, undergoes a natural cycle of changes throughout the year. Typically, the lake level is highest during the early summer months and lowest during the dead of winter. These fluctuations are related to seasonal changes in the amount of water flowing into and out of the lake. In-flow for Lake Erie includes drainage from the upper portion of the Great Lakes basin through the Detroit River, water from rivers flowing directly into the lake, contribution from ground water, and also from precipitation falling directly into the lake. Out-flow includes discharge to Lake Ontario through the Niagara River, evaporation, and any diversions or other withdrawals.

Long Term Fluctuations

   In addition to this annual fluctuation, the levels of the Great Lakes also exhibit long-term fluctuations that cycle between a much wider range of levels. These fluctuations result from cumulative effects of a prolonged and persistent deviation from average climatic conditions. Several successive seasons or years of above or below normal precipitation are usually required before a reversal of the current general trend can begin.

Recent Trends

   The level of Lake Erie generally ranged above normal for the last 30 or so years of the 20th century. These persistently high water levels reflect the above-normal precipitation that consistently fell in the Great Lakes basin, especially during the 20-year period prior to the record-high level year of 1986. During this 20-year period, precipitation accumulated to nearly 39 inches above normal, and for individual years was below normal in only four of those twenty years. The high levels reached during 1985-87 surpassed the previous high levels set in the early 1970s. Following drier years, most notably 1976-77 and 1987-89, lake levels declined to near normal during the late winter and early spring months, but quickly rebounded to above-normal by the summer months following spring runoff. In early 1996, lake levels again approached normal before rising sharply following above-normal precipitation in the upper Great Lakes basin. However, below normal precipitation and increased evaporation during late 1997 and 1998 resulted in Lake Erie level falling to below normal during spring 1999 for the first time since the late 1960's. The level of Lake Erie declined nearly 3 feet from the middle of 1998 until early 1999, a significant drop in water levels in the Great Lakes.

   Typically, the level of Lake Erie fluctuates about 14 inches during a given year. During 2002, the Lake level fluctuated quite a bit more than this amount, about 20 inches. After its steep decline from near record-high levels in 1997, the level of Lake Erie generally remained below average from early 1999 through mid-2004. However, a combination of favorable hydrologic conditions in late 2001 and early 2002 resulted in a marked recovery of lake levels, which hovered around average through the first half of 2002. The recovery was short lived as a rather hot and dry summer during 2002 negated these earlier improvements and lake levels fell back below average through mid-2004. Lake levels during the next 4 years reflected precipitation patterns, rising following extended periods of above normal precipitation and declining following prolonged periods of below normal precipitation. Following above normal precipitation, lake levels rose to above average from June 2004 through May 2005, from October 2006 through May 2007, and again from February 2008 through July 2008 while levels declined to below average during most of the remainder of this 4 year period following extended durations with below normal precipitation across the Great Lakes basin.

Short Term Predictions

   Above normal precipitation has fallen in the Great Lakes basin from late autumn 2008 through early spring 2009. During this period, precipitation in the Lake Erie basin has averaged about 5 inches above normal. This precipitation and the combination of other hydrologic factors such as evaporation and ice cover, have resulted in a 1.5 feet rise in the level of Lake Erie during this period. This time of the year is typically a period when the level of Lake Erie remains relatively stable. By January, the lake level had risen above the normal seasonal average. The U.S. Army Corps of Engineers predicts that, based on the hydrologic condition of the Great Lakes basin at the end of March and anticipated future weather conditions, the level of Lake Erie is expected to remain above normal for the foreseeable future, perhaps falling to near normal during late summer 2009. Deviations from the expected weather patterns could result in the level of Lake Erie ranging from 12 inches above normal to as much as 8 inches below the normal seasonal average.

Scott Kirk
Ohio Department of Natural Resources
Division of Water
Water Inventory Section
2045 Morse Rd., Bldg. B
Columbus, Ohio 43229-6693

Phone: (614) 265-6742
E-mail: scott.kirk@dnr.state.oh.us