Lakes and reservoirs are found throughout North America. The combination of extensive glaciations and widespread dam building has resulted in a continent that is rich in lakes of all sizes, from the smallest features tens of meters across to the Great Lakes, which might be considered inland seas. In this article the terms 'lake' and 'reservoir' will be used to signify water bodies of natural and human origins, respectively, and this distinction is the primary framework for organizing the discussion. The term 'water body' is used to indicate a lake or reservoir without regard to its origin.
The distribution of large lakes and reservoirs in North America is shown in Figure 1. This map includes 1835 water bodies averaging about 39 km2 in area. As is evident, both the largest water bodies and their highest concentrations are in eastern Canada and in adjacent portions of the United States. This is the area that was covered by continental ice sheets during the Pleistocene Epoch (—2 million to 12 thousand years ago). Although most of the features in this area are natural, many are reservoirs, especially in Quebec. The map also shows many large features outside the glaciated region. Some of these, particularly in the mountain system known as the North American Cordillera and including the Rocky Mountains, are of natural origin. Most of the water bodies outside the Cordillera and the glaciated area are reservoirs.
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