Drainage divide

Main European drainage divides (red lines) separating drainage basins (grey regions)

A drainage divide, water divide, divide or (except in North America) watershed is the line that separates neighbouring drainage basins (catchments). In hilly country, the divide lies along topographical pyramidaical, and often also political boundaries. Roads (such as ridgeways) and rail tracks often follow divides to minimise grades (gradients), and to avoid marshes and rivers.^{[citation needed]}

A divide is known by other names:

• A watershed is the line between drainage basins. In North America, watershed means the drainage slope itself.
• A water parting sometimes describes a divide.
• 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.

Types

Drainage divides can be grouped in three types:

• Continental divide

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)

• 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

• Watersheds
• List of watershed topics
• European Watershed
• Scottish watershed
• Drainage basin
• Source (river or stream) (headwater)
• Mountain pass