The neighboring hydrographic slopes of the Leblanc River are:

• north side: Gouin Reservoir, Bouzanquet Bay, Vincent Lake, Brochu Lake, Kettle Bay;
• east side: Atimokateiw River, Jean-Pierre River (Gouin Reservoir), Saint-Maurice River, Cypress River (La Tuque);
• south side: Decelles Lake, Bazin River, Norah Creek, Bellerive River, West Pichoui River;
• west side: Delage Lake, Five Mile Lake, Bureau Lake, Gouin Reservoir, Oskélanéo River.

The Leblanc River originates at the mouth of Decelles Lake (length: 5.7 kilometres (3.5 mi); altitude: 435 metres (1,427 ft)). This lake straddles the townships of Fréchette and Decelles. The mouth of this head lake is located at:

• 18.8 kilometres (11.7 mi) south-east of the mouth of the Leblanc River (confluence with Bouzanquet Bay of Gouin Reservoir);
• 22.8 kilometres (14.2 mi) southwest of the dam at the mouth of the Gouin Reservoir (confluence with the Saint-Maurice River);
• 54.8 kilometres (34.1 mi) north-east of the village center of Wemotaci, Quebec which is located along the Saint-Maurice River;
• 145 kilometres (90 mi) north-west of downtown La Tuque.^[2]

From the mouth of Decelles Lake, the course of the Leblanc River flows over 32.8 kilometres (20.4 mi) according to the following segments:

• 12.3 kilometres (7.6 mi) northeasterly to the west shore of Big Bear Lake;
• 3.6 kilometres (2.2 mi) north across Big Bear Lake (length: 5.0 kilometres (3.1 mi); altitude: 412 metres (1,352 ft)). Note: This lake straddles the townships of Leblanc and Decelles;
• 5.3 kilometres (3.3 mi) to the Northwest passing between two mountains, then crossing Lake Leblanc (length: 3.7 kilometres (2.3 mi); altitude: 401 metres (1,316 ft)), in full length, to its mouth;
• 5.7 kilometres (3.5 mi) northwesterly across a swamp area, then recovering the dump (coming from the north-east) of an unidentified lake and crossing over 0.2 kilometres (0.12 mi) the eastern part of Motard Lake, to its mouth;
• 5.9 kilometres (3.7 mi) northwesterly, forming a hook of 0.8 kilometres (0.50 mi) north-east at the beginning of the segment, to its mouth.^[3]

The confluence of the Leblanc River with the Gouin Reservoir is located at:

• 18.3 kilometres (11.4 mi) south-west of the Gouin dam;
• 110 kilometres (68 mi) south-east of the village center of Obedjiwan, Quebec;
• 55.4 kilometres (34.4 mi) north-west of the village center of Wemotaci, Quebec;
• 137 kilometres (85 mi) north-west of downtown La Tuque;
• 216 kilometres (134 mi) northwest of the mouth of the Saint-Maurice River (confluence with the St. Lawrence River at Trois-Rivières).

The Leblanc River flows on the east bank of De La Galette Lake (Gouin Reservoir) which is crossed by De La Galette River (Gouin Reservoir); the latest has a widening at this location of 1.9 kilometres (1.2 mi). From there, the current flows north-west on 1.3 kilometres (0.81 mi) to the mouth of the la Galette River; 9.5 kilometres (5.9 mi) northwesterly to the mouth of Bouzanquet Bay; then cross the Gouin Reservoir on 34.8 kilometres (21.6 mi) bypassing a large peninsula by the North, crossing Brochu Lake and Kikendatch Bay until Gouin dam.

• Saint-Maurice River
• Gouin Reservoir, a body of water
• Kikendatch Bay
• Brochu Lake, a body of water
• Bouzanquet Bay
• De la Galette River (Gouin Reservoir), a watercourse
• De la Galette Lake (Gouin Reservoir), a waterbody
• La Tuque, a city
• Haute-Mauricie, a territory corresponding to the town of La Tuque
• List of rivers of Quebec