Overview of the Issue: The Great Lakes Basin comprising of Lakes Superior, Michigan, Huron, Erie and Ontario make up the largest surface freshwater system on Earth and holds one-fifth of the world's supply of freshwater. To visualize this, " if only the Earth were flat and the lakes adaptable as buckets, there'd be enough H20 here to flood all the land of the Western Hemisphere under two feet of water" according to J. Mitchell. Each day, four trillion litres of water are pumped from the Great Lakes. As natural influences as well as human factors are putting tremendous pressures on this water system, the water levels are dropping at an alarming rate. The falling water levels present an enormous environmental impact to thousands of species of plant and wildlife and to the 45 million inhabitants who dwell in the Great Lakes area according to the Council of Canadians. Lake Huron and Lake Michigan are the two lakes that have been the most affected.
Environmental Impacts: There are several theories explaining the declining water levels. The water levels of the Great Lakes are dependent on three major components: They are the evaporation off of the surface of lakes, the precipitation directly on to the surface of lakes and the runoff of precipitation coming from the land (groundwater and streams). One of the major causes that has occurred over the years is the change in weather patterns. Changes in water supply are driven by climatic factors including precipitation and temperature. The Great Lakes are particularly affected by winters. If the winters are severe with higher snowfalls and colder temperatures, ice cover (which acts as an insulation), will result in higher water levels. If the winters are milder with warmer temperatures there is less ice coverage resulting in more evaporation and decreasing the water level. “Overall, the Great Lakes have lost 71% of their ice cover since 1973” ,according to the Watershed Council, most of which is due to increasing air and water temperatures. More water is being evaporated than is being precipitated therefore resulting in a 9 - 17 cm drop of water in the Great Lakes. Studies released in 2009 have indicated that climate change played a big factor in the drop of 25 cm in Lakes Huron & Michigan relative to Lake Erie between the years of 1963 – 2007 according to T. Thanh Ha and D. Biac
Global Warming: Although the Earth's climate goes through naturally-occurring cycles, the human impact of global warming is accelerating the changes in lake levels. Shorter winters and dry, hot summers mean more water evaporating from the lakes than being replaced through precipitation.
Dredging of the St. Clair River: The St. Clair River flows out of Lake Huron and has been dredged several times in the past century to accommodate large commercial vessels. This has caused a significant increase in the flow of water out of Lake Huron and Lake Michigan resulting in water levels lowering 7 -14 cm. In...