Watersheds

What is a watershed ?

A watershed, also known as a catchment basin or area, includes all of the land that is drained by a watercourse and its tributaries. It is a dynamic and complex web of natural resources - soil, water, plants and animals - where we live, work and play.
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How does the hydrologic cycle affect a watershed?

An understanding of the hydrologic cycle on a watershed basis is essential for implementing an ecosystem approach to water management.
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Watershed delineation

Map of the province of Ontario depicting the three primary watersheds of Ontario.

Primary watersheds in Ontario

There are three primary watersheds in the province of Ontario - the Great Lakes, Hudson Bay and the Nelson.

These three primary divisions have been divided into 17 secondary divisions. Most secondary divisions are either large river systems or groupings of small coastal streams. Ontario's secondary watershed divisions range in size from 4,000 - 150,000 square kilometres.

The secondary divisions are further sub-divided into 144 tertiary divisions ranging in size from 700 - 31,000 square kilometres.

Cross Section of a Typical Ontario Watershed

Features of a watershed

Include size, boundary, terrain, soil type, land uses, natural resource uses as well as social, economic and employment trends.