What is a watershed?

A watershed is an area of land from which rainfall and snowmelt naturally drain into a common water body such as a creek, river, lake, or wetland. Water flows downhill from higher elevations (mountains and hills) through numerous rivulets and smaller streams, eventually discharging into the larger water body. Several smaller watersheds can make up a larger watershed, which may also be called a basin. Catchment and hydrologic unit are other terms that may also refer to a watershed.

Watersheds are divided based on topography, with specific areas of higher elevation separating different water bodies. A broad example of this would be the Rocky Mountains dividing the Pacific and Atlantic Ocean watersheds in North America.

Some watersheds do not have outflows connecting them to other basins. Rain and snowmelt are retained in the watershed and do not exit. The Pakowki Lake watershed is like this, and is considered an endorheic basin.

The SEAWA watershed consists of two geographically adjacent but hydrologically separate watersheds: The South Saskatchewan River watershed within Alberta, and the Pakowki Lake watershed. 

Sub-watersheds
Municipalities

Important things to remember about watersheds are:

  • What we do on the land affects water quality for all communities living downstream
  • Our ground water and surface water are very much connected to each other