Reserve System – the Great Lakes, Lake Superior subregion. The Lake Superior Reserve and the Old Woman Creek (Lake Erie in Ohio) are the only Great Lakes freshwater estuaries in the Reserve System. This subregion contains all of Lake Superior and its freshwater estuaries. One of these estuaries formed where the waters of the St. Louis River enter Lake Superior. Lake Superior, which is bordered by Michigan, Minnesota, Wisconsin and Ontario, Canada, is the largest of the Great Lakes and the most pristine. Freshwater estuaries occur where rivers and Great Lakes water mix in shallow wetlands located near the mouth of a river. The Reserve contains all three common defining characteristics of a Great Lakes freshwater estuary including a) presence of a drowned river mouth b) adequate zone of transition between lake and river water and c) influence from tide or seiche. References External links National Estuarine Research Reserves of the United States Protected areas of Douglas County, Wisconsin Estuaries of Wisconsin Landforms of Douglas County, Wisconsin Protected areas established in 2010 2010 establishments in Wisconsin University of Wisconsin–Superior