Watershed, Primary

Note: this Watershed, Primary data has been replaced by the Ontario Watershed Boundaries.

A watershed, also known as a catchment basin, includes all land that is drained by a watercourse and its tributaries.

Watersheds are split into four categories:

  • primary
  • secondary
  • tertiary
  • quaternary

Ontario has three primary watersheds:

  • Great Lakes – St. Lawrence
  • Southwestern Hudson Bay
  • Nelson River

These divisions are based on the federal framework originally known as the Water Resources Index Inventory Filing System.


Ontario's Open Data Team opengov@ontario.ca


Data Available

The data described here is available for you to use. [Learn more]
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Covers 2010-01-01 - 2020-07-02

Supporting Files

Additional Info

Field Value
Geographic coverage Ontario
Geography Breakdown None
Source URL/Address
Author Email
Maintainer branch
Last Validated Date 2020-07-17
Update frequency As required
Access instructions