Lake Rohault and Poutrincourt Lake constitute the most important water bodies of the zone of the higher part of the Normandin River which is a tributary of the Ashuapmushuan River that empties into Lac Saint-Jean. It is located at the western end of the MRC Le Domaine-du-Roy. This lake has a length of 16.3 kilometres (10.1 mi), a maximum width of 5.6 kilometres (3.5 mi) and an altitude of 402 metres (1,319 ft). The outline of the lake has a complex shape.

Lake Rohault has a peninsula attached to the north shore and extending over 8.3 kilometres (5.2 mi) towards the center of the lake. This lake has about a hundred islands, the largest of which lies on the North 5.9 kilometres (3.7 mi) side along the west shore of the lake. A strip of land stretching northward on 11.3 kilometres (7.0 mi) distinguishes Lake Rohault and Lake Bouteroue (located on the east side). On the east side, Gaudreau Bay extends northward for 11.6 kilometres (7.2 mi). The current flows through this bay to the mouth of the lake at the bottom of another bay on the east side.

The mouth of Lake Rohault is located at:

• 8.5 kilometres (5.3 mi) north-west of the mouth of the Bouteroue Lake;
• 10.2 kilometres (6.3 mi) northwest of the mouth of Bouteroue Creek (confluence with the Normandin River);
• 19.7 kilometres (12.2 mi) northwest of the mouth of Poutrincourt Lake;
• 38.1 kilometres (23.7 mi) northwest of the mouth of Ashuapmushuan Lake;
• 160.6 kilometres (99.8 mi) south-west of the mouth of the Ashuapmushuan River (confluence with lac Saint-Jean.^[1]

The main hydrographic slopes near Lake Rohault are:

• North side: Mannard Lake, Nemenjiche River, La Dauversière Lake, Énard River, Chibougamau Lake;
• East side: Bouteroue Lake, Normandin River, Bouteroue Creek, Nicabau Lake;
• South side: Robert Lake (Opawica River), Feuquières Lake, Finbar Lake, Ventadour River, Titipiti River, Pierrefonds River;
• West side: Nemenjiche Lake, Opawica River, Gabriel Lake (Opawica River), Surprise Lake (Roy River), Cawcot River.

From the road bridge at the mouth of Rohault Lake, the current:

• crosses the Bouteroue Lake on the South 10.4 kilometres (6.5 mi) to its mouth;
• crosses south-east, then north-east, on an unidentified lake to the dam at its mouth;
• descend Bouteroue Creek on 7.0 kilometres (4.3 mi) to a bay south of Nicabau Lake, the southern portion of which is crossed by the Normandin River;

Note: The Normandin River flows southeast to Ashuapmushuan Lake is the head lake of the Ashuapmushuan River.