Lake Superior Water Level at Record Low

Lake Superior's water levels have been reaching record lows the past few months. North America's largest Great Lake and the world's largest freshwater lake by surface area, Lake Superior and its channels are vital waterways for commercial shippers and important sources of hydroelectric power. However, with the lake's current water levels, shippers are unable to transport full cargo loads and hydroelectric power plants must run at less than 100 percent capacity.

According to statistics from the U.S. Army Corps of Engineers, Lake Superior's current average water level is about 0.5 meters below the lake's long-term average level. Just on Tuesday, October 2, the lake's water level was 183.066 meters, which is less than the recorded minimum of 183.10 meters for the month of October, recorded in 1925. According to a U.S. Army Corps of Engineers' press release from August 2007, "Since April 1998 Lake Superior has been below its long-term average (1918-2006) and is currently in the longest period of below average water levels in history."

Many different factors are affecting the lake's water levels. The U.S. Army Corps of Engineers states, "Water levels on Lake Superior are highly dependent on the supply of water received by the Lake Superior watershed. The hydrologic cycle has many components that affect the supply of water to the lake such as precipitation, evaporation and runoff. Natural factors contributing to these record low water levels on Lake Superior include:

  • Precipitation in 2007 through July is an inch (25 mm) below average.

  • Precipitation in 2006 was close to 6 inches (150 mm) below average.

  • Precipitation in 2005 was about an inch and a half (37 mm) below average.

  • December 2006 was a relatively warm month, leading to slower than normal ice growth. When very cold air temps arrived in mid-January, evaporation rates greatly increased. Evaporation in January and February of 2007 was much above average. In 2007, only the months of May and June saw below average evaporation.

  • The amount of water available from the winter 2006/2007 snow pack was 60% below average.

  • Portions of the Lake Superior watershed have been classified as moderate drought or drier since May 2006.

The above factors influence the amount of water available to the lake (known as the supply) and largely contribute to water levels. Regulation of Lake Superior outflow also has an effect on water levels but to a much lesser extent. …The major influence on Lake Superior water levels is the hydrologic cycle and the current dry conditions are having a substantial effect on water levels." Regardless of the causes, the U.S. Corps of Engineers projects that Lake Superior's water level will only continue to drop in the near future, as seen in the graph here.

Lake Superior is not the only lake that is suffering from low water levels. The other Great Lakes are also significantly low. Additionally, water levels of Lake Powell on the border of Arizona and Utah and Lake Mead in Nevada are both dwindling. Lake Okeechobee in Florida recently hit record lows as well. These low water levels affect both the environment and economy. Environmentally, wetlands are drying up and beaches are appearing where they never were before. Economically, cargo ships, in fear of scraping the lakes' bottoms, can not carry full loads. Moreover, many power plants can only run at half capacity.

Many see Congress' recent passage of the Water Resources Development Act (WRDA) of 2007, which, according to the American Association of Port Authorities (AAPA), "addresses a seven-year backlog of U.S. Army Corps of Engineers programs," as a partial solution to dropping water levels. One program the WRDA addresses is the dredging of the Great Lakes, which the U.S. Army Corps of Engineers calls "necessary to allow for safe commercial navigation and recreational boating." However, others speculate that dredging causes water to flow downstream faster and are worried that more dredging will just decrease water levels even more. In fact, the International Joint Commission actually just began a five-year study of the effect of dredging in the St. Clair River. Regardless, there is no disputing the fact that water levels are currently dropping drastically in various places, most significantly Lake Superior.