Secondary forest roads serve the southern part of the hydrographic side of Lake Fronsac.

Located in a forest zone in the unorganized territory of Lac-Pikauba in the Laurentides Wildlife Reserve, the lake Fronsac (length: 2.2 kilometres (1.4 mi); altitude: 821 metres (2,694 ft)) is located on the western slope of the Malbaie River valley.

This mouth is located at: From the mouth of Lake Fronsac, the current crosses 3.1 kilometres (1.9 mi) to the east at Lac à Jack; then descend on 2.1 kilometres (1.3 mi) to the south the outlet of the lake at Jack; from there, the current follows the course of the Malbaie river on 148.9 kilometres (92.5 mi) with a drop in level of 818 metres (2,684 ft) which pours into La Malbaie in the St. Lawrence River.

[1] The term "Fronsac" turns out to be a commune in the southwest of France, located in the department of Gironde.

The toponym "Lac Fronsac" was formalized on December 5, 1968 at the Place Names Bank of the Commission de toponymie du Québec.