The valley of the Rivière à la Loutre is mainly served by forest roads including the R-0202 in the upper part.

[1] Rivière à la Loutre has its source at the mouth of Lac à la Truite (length: 1.26 km (0.78 mi); altitude: 255 m (837 ft)) located in the unorganized territory of Rivière-Mistassini, just 0.24 km (0.15 mi) north-west of the limit of the municipality of Saint-Thomas-Didyme.

The mouth of Lac à la Truite is located in a forest zone in the Rivière-Mistassini territory, at: From the mouth of Lac à la Truite, the Rivière à la Loutre flows over 10.5 km (6.5 mi), with a drop of 75 m (246 ft), entirely in forest area, depending on the segments following: Rivière à la Loutre flows into a bend in the river on the north bank of the Ashuapmushuan river at 4.0 km (2.5 mi) downstream from the confluence of the Petite rivière aux Saumons and upstream of the Rapide Pas background.

The confluence of the Rivière à la Loutre is located at: From the mouth of Rivière à la Loutre, the current descends the course of the Ashuapmushuan River on 58.5 km (36.4 mi), then crosses lac Saint-Jean eastward on 41.1 km (25.5 mi) (ie its full length), follows the course of the Saguenay River via la Petite Décharge on 172.3 km (107.1 mi) eastward to at Tadoussac where it meets the Estuary of Saint Lawrence.

[1] The toponym "rivière à la Loutre" was made official on December 5, 1968, at the Place Names Bank of the Commission de toponymie du Québec.