A drainage divide, water divide, divide or (outside North America) watershed is the line separating neighbouring drainage basins (catchments). In hilly country, the divide lies along topographical peaks and ridges, but in flat country (especially where the ground is marshy) the divide may be invisible – just a more or less notional line on the ground on either side of which falling raindrops will start a 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.

A divide is also known as:

• A watershed, the line between drainage basins – shedding is an old term for splitting or dividing, so it is the line which divides the water (however in North America "watershed" has come to mean the drainage basin itself);

• a water parting;

• a height of land (in Canada).

Types

Drainage divides can be grouped in three types:

• Continental divide

• Major drainage divide

• Minor drainage divide

Drainage divides are a hindrance to river navigation. In pre-industrial times water divides were crossed at portages. Later, canals were built to connect the adjoining drainage basins.

See also

• European Watershed

• Mountain pass

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