The South Nation River is 175 km long and drains an almost flat plain, dropping only 85 m from the headwaters north of Brockville and empties into the Ottawa River, near Plantagenet. Headwater features are important in the South Nation Watershed because they help to protect land, people and property from flooding, contribute to water quantity and quality and provide essential habitat for plants and animals. These features include wetlands and streams that can be wet all year or only some of the time, and form the source of the river.