GRAND RIVER, Ontario The Grand River and its tributaries comprise the largest watershed in Southern Ontario, 7000 square kilometres, from the Dundalk Plateau to Lake Erie. At one time, the river was a magnet for settlement based on its ability to generate power for its small communities. Today, it provides nesting habitat for waterfowl, and a refuge for rare species in its Carolinian forest. The River also has significant wetlands, and magnificent geological features. Efforts at flood control have harnessed its waters and reinforced some of its boundaries, but at least one-fifth of its length retains its wild, natural character.