The boundaries of Whitchurch–Stouffville contain a watershed divide. Streams and rivers at the top of the Oak Ridges Moraine flow northward into the Lake Simcoe basin, part of the Lake Huron watershed. The southern sections (south of Bloomington Road) make up the headwaters of the Rouge River and Duffins Creek, both of which flow into the Lake Ontario basin. These headwaters include many smaller streams and creeks throughout southern Whitchurch–Stouffville. Their identification and protection, plus reforestation in these area, has been identified as urgent for rebuilding water-capacity in the Rouge River watershed which can off-set the worst environmental impacts (e.g., flash flooding, erosion and ground water contamination) of rapid urbanization. The heavily wooded Vivian Infiltration Area is an environmentally significant hydrological infiltration area that contributes groundwater to the Oak Ridges aquifer complex.