For the purposes of this virtual exhibit, the Lake Saint-Pierre biosphere reserve has been subdivided into two main sections: the Lake Saint-Pierre archipelago and Lake Saint-Pierre.
Lake Saint-Pierre is 35 km long and 15 km wide, with a surface area of approximately 500 km2. The average depth of the lake is 3 m, but it is traversed by the St. Lawrence Seaway, a ship channel 11.3 m deep and 245 m wide. Lake Saint-Pierre is a broadening of the St. Lawrence River.
The section on Lake Saint-Pierre covers the entire lake, as well as its northern and southern shores. The northern boundary runs from La Grande Pointe (just after Îles de la Girodeau) in the west to Trois-Rivières in the east, while the southern boundary starts at the mouth of the Saint-François River to the west and runs east to Bécancour. Although they are located slightly east of Lake Saint-Pierre, Trois-Rivières and Bécancour have been included in this exhibit because they are part of the Lake Saint-Pierre Biosphere Reserve.