Great Lakes' retention/replacement time

The Great Lakes contain the largest supply of freshwater in the world, holding about 18% of the world’s total freshwater and about 90% of the United States’ total freshwater. The Lakes are a series of five interconnecting large lakes, one small lake, four connecting channels, and the St. Lawrence Seaway. Combined, the lakes cover an area of over 94,000 square miles (245,000 square kilometers) and contain over 5,400 cubic miles (23,000 cubic kilometers) of water
*Retention/Replacement time: The amount of time it takes for lakes to get rid of pollutants.