From the railway of Canadian National, the very serpentine river crosses several wetland areas, a distance of about 5.8 km (direct line) to fund a flared valley to its mouth.

A small delta appears at the mouth of the “Rivière du Milieu" which empties into the north-east of Mékinac Lake.

The mouth of the «Rière à l’eau morte» is located 4 km (measured in a straight line) upstream of the mouth of the «Rivière du Milieu" or 2.1 km downstream of the railway bridge crossing the “Rivière du milieu”.

The Government of Québec recognized one of the few sanctuaries for reproduction of aquatic fauna, covering a segment of the river, the fishing activities are therefore prohibited throughout year.

The name "Rivière du Milieu” (Mekinac) means that this river is midway on the rail route between Hervey-Jonction and La Tuque.