This watercourse crosses the unorganized territory of Lac-Ashuapmushuan, in the Le Domaine-du-Roy Regional County Municipality, in the administrative region of Saguenay–Lac-Saint-Jean and the territory of La Tuque, in Mauricie.

This watercourse is part of the watershed of the Saint-Maurice River which flows at Trois-Rivières on the north shore of the Saint Lawrence River.

The surface of the river is generally frozen from mid-December to the end of March.

The Pierriche du Milieu river has its source at the mouth of an unnamed lake (length: 0.3 km (0.19 mi); altitude: 514 m (1,686 ft)), located in unorganized territory from Lac-Ashuapmushuan.

This confluence is located at: The toponym Rivière Pierriche du Milieu was formalized on December 5, 1968, at the Commission de toponymie du Québec.