The Cannon River flows through the town of Northfield. The river rises south of Northfield and flows north through the city, emptying into the Mississippi River just north of Red Wing, Minnesota.
The Cannon River Watershed is an area is 1,462 square miles and includes land in six counties: Dakota, Goodhue, Le Sueur, Rice, Steele, and Waseca. The largest tributary to the Cannon is the Straight River.
The Lower Arb is centered on the Cannon River as it flows east from the campus.