This collection represents the authoritative watershed boundaries for Ontario. The data is based on a framework similar to the [Atlas of Canada Fundamental Drainage Areas](https://open.canada.ca/data/en/dataset/a4b190fe-e090-4e6d-881e-b87956c07977) and the [United States Watershed Boundary Dataset](https://www.usgs.gov/core-science-systems/ngp/national-hydrography/watershed-boundary-dataset?qt-science_support_page_related_con=4#qt-science_support_page_related_con), however it adopts a more stringent scientific approach to watershed delineation. The Ontario Watershed Boundaries (OWB) collection includes five data classes: * OWB main: all levels from primary to quaternary and 5th and 6th levels in select areas * OWB primary: all primary watersheds or major drainage areas in the Canadian classification * OWB secondary: all secondary watersheds or sub drainage areas * OWB tertiary: all tertiary watersheds or sub sub drainage areas * OWB quaternary: all quaternary watersheds or 6-digit drainage areas. The OWB data replaces the following data classes: * [Provincial Watersheds, Historical](https://data.ontario.ca/dataset/provincial-watersheds-historical)