The Rouge River watershed starts in the Oak Ridges Moraine and flows south to Lake Ontario.
The watershed includes all the lands which drain to the Rouge River and its tributaries, including Little Rouge Creek. The southern third of the watershed is protected by Rouge National Urban Park, with a small established area of urban development to the west of the park. The middle and western sections of the watershed are urban with sparse natural cover outside of the park. The northeastern areas of the watershed are primarily rural and agricultural with small towns and villages. The watershed spans the Regions of York and Durham, cities of Toronto, Pickering, and Markham, and the towns of Richmond Hill and Whitchurch-Stouffville.
* 336 Km2 watershed size