Geography 2011A/B : The Great Lakes Atlas
18 Nov 2013
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Document Summary
The great lakes: an environmental atlas and resource book. Lakes contain about 23,000 km3 of water, covering a total of 244,000 km2. Largest system of freshwater on earth, 18% of the world supply. Sensitive to effects of many pollutants: runoff of soils and farm chemicals from agricultural lands, waste from cities, discharges from industrial areas and leachate from disposal sites, atmospheric pollutants that fall with rain or snow. Northern great lakes climate is cold, terrain is dominated by granite bedrock (canadian shield) Southern great lakes climate is warmer, lands are fertile and agricultural. Lake superior largest, deepest, and coldest of the five: retention time of 191 years. Retention time measure based on the volume of water in the lake and the mean rate of outflow: most of the basin is forested, little agriculture because of cool climate and poor soils. Forest and sparse population result in few pollutants, except via airborne transport.
