Great Lake levels take a plunge

Low precipitation levels and increased evaporation due to warmer temperatures have contributed to the single largest annual drop in the water levels of lakes Erie and Ontario since 1931. Although scientists say it is still too soon to determine whether or not climate change is responsible for the plunge, the decline has generated both concern and opportunity for shoreline residents.

Lower waters mean larger beaches—a major draw for tourists and shoreline property owners—reduce flood damage, and provide municipalities with a chance to clean up local waterways. The surrounding wetlands also flourish during low periods when their seed banks surface and begin to germinate. At the same time, low levels mean costly dredging efforts for commercial navigation and marina channels, force freighters to carry lighter loads, and reduce spawning areas for many species of fish.

Using monitoring data collected in cooperation with the Department of Fisheries and Oceans from more than 30 gauges across the Great Lakes, and historic and hydrological information collected by other Canadian and American agencies over the past 80 years, scientists at Environment Canada are studying changing lake levels to improve their ability to forecast future events and better understand the impact of climate and land-based activities on water levels. Their studies show that although levels in lakes Erie and Ontario plummeted more than half a metre between May 1998 and May 1999, similar trends have occurred in the past, and Great Lakes water levels are still some 60 centimetres above the lowest levels recorded this century.

Conveying this information and improving the public's understanding of lake levels are two of the goals of Environment Canada's research in this field. Over the years, the number of people using the Great Lakes for recreational purposes has increased dramatically—and so, too, has the potential for impacts from fluctuating levels, such as floods, moving sandbars and erosion.

The Department's Great Lakes Water Level Information Office in Burlington, Ontario, helps various sectors of the economy deal with these impacts by providing regular information on lake levels to clients ranging from commercial fisheries to the media. For municipalities, this information is critical for budgeting such works projects as dredging harbours, extending intake pipes for water supplies, and covering exposed outflows. It is also critical to boaters in avoiding sandbars and rocks.

These data are also used for resource management to determine how much water can be released through dams at different times of the year. Most recently, the Department's studies have been used in developing a new model for determining the impact of future land-based development along the Detroit and St. Clair rivers. The St. Clair and Detroit Rivers' Encroachment Analysis will look at how infill from development and aquatic habitat projects changes the rivers' levels and flows, and aims to prevent the cumulative impacts of these projects from leading to increased ice jams, flooding and erosion.

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