The Great Lakes are the largest surface freshwater system on the Earth, with 84% of North America’s surface freshwater and 21% of the world’s supply. Only the polar ice caps contain more fresh water. More than 30 million people live in the Great Lakes basin, and the daily activities of these people, from the water consumed to the waste returned, directly affect the Great Lakes environments.
In spite of their large size, the Great Lakes are sensitive to the effects of a wide range of pollutants. Major stresses on the lakes include toxic and nutrient pollution, invasive species and habitat degradation. Sources of pollution include the runoff of soils and farm chemicals from agricultural lands, waste from cities, discharges from industrial areas and leachate from disposal sites.
The large surface area of the lakes also makes them vulnerable to direct atmospheric pollutants that fall as rain, snow, or dust on the lake surface, or exchange as gases with the lake water. Outflows from the Great Lakes are relatively small in comparison with the total volume of water, so pollutants that enter the lakes are retained in the system and become more concentrated with time.
ELPC’s work to improve nutrient and other water quality standards and reduce mercury and other pollution from old coal-fired power plants, as well as other efforts, are contributing to the region’s ability to protect and preserve this important natural resource.