It is very difficult to reverse the effects of water pollution. Natural processes that cleanse the water can take years, decades, or even centuries, and even with costly technological processes, it can take years to remove all of the harmful substances from the water.
The Great Lakes are a set of five lakes in Canada and the United States, connected by approximately 5,000 tributaries. The five lakes are Lake Superior, Lake Michigan, Lake Huron, Lake Erie and Lake Ontario. The Great Lakes basin includes two countries, eight states, one province, dozens of tribes and First Nations communities and hundreds of local municipal and regional governments.