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The Lake Ontario Drainage Basin

Lake Ontario is the last of the chain of Great Lakes that straddle the Canada/United States border. Its shoreline is bordered by the Province of Ontario on the Canadian side and New York State on the US side. Lake Ontario is the smallest of the Great Lakes, with a surface area of 18 960 square kilometres, but it has the highest ratio of watershed area to lake surface area.

A map of the Lake Ontario drainage basin, and the international border between Canada and the United States. Areas of Concern are shown in Hamilton Harbour, Metro Toronto, Port Hope, Bay of Quinte, Rochester Embayment, Eighteen Mile Creek, Niagara River (New York) and Niagara River (Ontario). The Oswego River Delisted Area of Concern is also shown.

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