The Great Lakes are the largest system of fresh water lakes in the world, shared by the United States and Canada. They make up 95% of the surface freshwater in the United States and have 10,000 miles of coastline (including connecting channels, mainland and islands)—more than the both the American Pacific and Atlantic coastlines combined.

While 20% of fresh water in all of the world’s lakes is in Canadian lakes, only 6.5% of the world’s renewable water supply is in Canada.

Toronto is located in Southern Ontario, on the northwestern shore of Lake Ontario, and features a broad sloping plateau intersected by an extensive network of rivers, deep ravines, and urban forest.

Below are six of the most pressing issues facing this precious and extremely fragile natural resource: