LAKES
The North American Great Lakes contain nearly 20% of the world’s freshwater, much of it originally deposited by melting glaciers during the last ice age. Only a very small percentage of Great Lakes water is renewed each year through runoff, precipitation, and groundwater. Most of the water in the Great Lakes eventually enters the Atlantic Ocean via the St. Lawrence River, the rest flows to the Gulf of Mexico through large rivers in the southern basins. The region is also dotted with hundreds of thousands of smaller lakes and wetlands.