Great Lakes - St. Lawrence Basin Watersheds

Coordinate system: 4269 - "NAD83"


Revision Note: Please note that this dataset has been revised and is available from the Land Information Ontario (LIO) Warehouse.

The Great Lakes-St. Lawrence River Basin is divided into the following five watersheds, each of which consists of the area described by the regulations:

  • 1. The Lake Superior watershed
  • 2. The Lake Huron watershed
  • 3. The Lake Erie watershed
  • 4. The Lake Ontario watershed
  • 5. The St. Lawrence River watershed. 2007, c. 12, s. 1 (12).

The Great Lakes-St. Lawrence Basin watersheds are defined in Section 34.5(2) of the Ontario Water Resources Act (OWRA).

The Great Lake divisions are derived from the Provincial Watersheds of Ontario (eg. the Secondary and Quaternary Watershed definitions), which are based on the Natural Resources Canada / Water Survey of Canada 'Drainage Area' reporting framework originally known as the Water Resources Index Inventory Filing System (1922). For more information, please refer to the metadata for the Secondary Watersheds of Ontario.

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