Lake retention time
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Lake retention time refers to measurements based on the volume of water in a lake and the average rate of outflow. It represents the amount of time it takes for a substance introduced into a lake to flow out of it again. This metric depends on a number of factors, including lake volume, number of rivers flowing in and out of the lake, and average depth. The retention time is especially important where pollutants are concerned.
[edit] Great Lakes
The greatest lake system in the United States is the Great Lakes system. The EPA has made available the retention time, in years, for each of the Great Lakes.
- Lake Superior: 191 years
- Lake Michigan: 99 years
- Lake Huron: 22 years
- Lake Erie: 2.6 years
- Lake Ontario: 6 years