A watershed is the area of land that catches rain and snow which drains or seeps into a common water body such as a marsh, stream, river, or lake.

Watersheds include all water and water-dependent land features, such as wetlands, forests, towns, humans and other living things. They are of differing shapes and sizes, and cut across municipalities, provinces and countries. Watersheds are separated from one another by a land ridge or divide.

One way to identify watershed boundaries is by connecting all of the highest points of the land in the area around the receiving body of water.

A Watershed Example

Every point on the surface of the Earth is situated in a watershed. Watersheds are defined by the natural landscape, and as a result often do not align with political boundaries. However when a negative impact such as pollution from an industrial source is emitted into the air or water from one location, the effects can be felt throughout the watershed.

While there are often a number of different communities within a watershed, the best approach to protecting and preserving an ecosystem is to work together within the boundaries of the watershed.

Next: Water Quality

Adapted from Pollution Probe's Source Water Protection Primer