Drainage divide

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Drainage divides (red lines) separating drainage basins (grey regions)

A drainage divide, water divide, divide, ridgeline[1] or (except in North America) watershed (Brit) is the line that separates neighbouring drainage basins (catchments, or in North America 'a watershed'). In hilly country, the divide lies along topographical ridges (A ridgeline and may be in the form of a single range of hills or mountains; known as a Dividing range). In flat country—especially where the ground is marshy—the divide may harder to define.

A divide is known by other names:

  • A watershed is the line between drainage basins. In North America, watershed means the drained land (relative to other rivers or to seas) itself.
  • A water parting
  • In Canada, some say a height of land.
  • A valley floor divide is a low drainage divide that runs across a valley, sometimes created by deposition or stream capture.
  • Since ridgelines are easy to see and agree about drainage divides are ofttimes natural borders defining political boundaries.

Types

Drainage divides can be grouped in three types:

A divide in which waters on each side flow to different oceans (for example: the Congo-Nile Divide)
  • Major drainage divide
Waters on each side of the divide never meet, but do flow into the same ocean (for example: the divide between the Yellow River basin and the Yangtze, or a more subtle example the Schuylkill-Lehigh divide at Pisgah Mountain in Pennsylvania, where two minor creeks divide to flow and grow east and west respectively joining the Lehigh River and Delaware River or the Susquehanna River and Potomac River each tributary complex having separate outlets into the Atlantic.)
  • Minor drainage divide
Waters part, but eventually rejoin at a river confluence (for example: the Mississippi and Missouri divides)

Drainage divides hinder river navigation. In pre-industrial times, water divides were crossed at portages. Later, canals connected adjoining drainage basins.

See also

Wikimedia Commons has media related to Drainage divides.
Wikimedia Commons has media related to Mountain saddles.

Footnotes and References

References

Footnotes

  1. ↑


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