Manicouagan Reservoir is on the Canadian Shield which is Precambrian in origin and similar in type to the Scandinavian Shield. It covers more than 90% of the province and is located north of the St. Lawrence River. This region is characterized by a disorganized collection of the hills with rounded peaks rarely more than 1,500 m high. The depressions between the hills are frequently occupied by lakes and rivers. This is why, depending on the sector, 20 to 50% of the region's surface is occupied by aquatic habitats. In this region, we find all of the major reservoirs built by Hydro-Quebec (e. g. the La Grande Project Area near James Bay).

The Manicouagan Reservoir is the most important reservoir of the Manicouagan Hydroelectric Complex. This reservoir is the result of the impoundment of two arched lakes (Manicouagan and Mouchalagan) and rivers. When the impoundment was completed, the reservoir took a final circle form with an island in the middle (Ile Rene-Levasseur). This circle form and the pattern of the local topography is the result of the impact of a meteorite which changed the nature of the rocks and affected the geological structure. The water of the reservoir is poor in mineral or organic elements and lightly acid. The water is as clear as all nordic lakes and has a low productivity. Situated at approximately 220 kilometers south of the reservoir, Baie-Comeau is the regional centre of this part of the North Shore (Q).