The main neighboring hydrographic slopes of the Saint-Régis river are: With a length of 19.2 kilometres (11.9 mi) and covering an area of 92 kilometres (57.17 mi), the Saint-Régis river takes its source from a set of agricultural streams around the village of Saint-Isidore, located northeast of the town of Saint-Rémi, east of the town of Mercier and south of Châteauguay.

[1] The river takes its source in a dense network of waterways and agricultural ditches which drain the northern flank of the Plateau de Saint-Michel.

This topographic entity advances westward to Mercier, thus marking the boundary of the watershed between the Saint-Régis river and the rivière de l'Esturgeon.

The regional aquifer is recharged in the Adirondacks, the United States and to a lesser extent in the Rock, southwest of Huntington and Covey Hill.

The toponym "Rivière Saint-Régis" was made official on December 5, 1968, at the Commission de toponymie du Québec.

[4] During flood prevention work, the section of the river between Route 132 and the mouth was completely drained for a period of 48 hours.