The surface of Lac F.X.-Lemieux is usually frozen from the beginning of December to the end of March, however safe circulation on the ice is generally done from mid-December to mid-March.

Then the current veers westwards zigzagging to go to flow on the east bank of the lac aux Rognons which is crossed by the Métabetchouane River.

From the mouth of the Métabetchouane river on the south shore of Lac Saint-Jean, the current crosses the latter on 22.8 kilometres (14.2 mi) towards the northeast, then follows the course of the Saguenay river via La Petite Décharge on 172.3 kilometres (107.1 mi) until Tadoussac where it merges with the Saint Lawrence estuary.

[2] This toponym designation evokes the memory of François-Xavier Lemieux, Deputy Minister of Lands and Forests of Quebec from 1924 to 1936.

He was first secretary to Adélard Turgeon from 1900 to 1909, then to Jules Allard from 1909 to 1919 and, finally, to Honoré Mercier son until 1924, all three having successively occupied the post of minister des Terres et Forêts.