Scientists Declare Great Lakes Nonrenewable, Citing Minimal Annual Water Renewal
Scientists have determined that the Great Lakes, which contain approximately 21 percent of the planet's surface fresh water, are effectively nonrenewable on a human timescale. Despite their vast volume, less than one percent of this water renews annually through rain, snowmelt, runoff, and groundwater. This minimal renewal rate means that water leaving the basin does not return, and contaminants that enter the system tend to linger and become more concentrated rather than flushing out. The U.S. Environmental Protection Agency (EPA) notes that the Great Lakes account for 84 percent of North American surface fresh water and 95 percent of the U.S. surface supply. The lakes were formed by retreating ice sheets roughly 10,000 years ago, and the water they hold is largely a glacial legacy, not a continuously replenishing resource. This finding has significant implications for the 40 million residents of the United States and Canada who rely on these lakes for drinking water. 
