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

A drainage divide, water divide, divide or in North America watershed is the line that separates neighbouring drainage basins (catchments). In hilly country, the divide lies along topographical peaks and ridges, 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 an invisible, more or less notional line on the ground on either side of which falling raindrops journey to different rivers, and even to different sides of a region or continent.

Drainage divides are important geographical, 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. Shedding is an old term for splitting or dividing, so it is the line that divides the water. In North America, however, 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[link]

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 Nile, Congo, and Lunghin Pass triple 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[link]

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

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