water parting

a watershed or divide.

Origin of water parting

First recorded in 1855–60

The crest of the water-parting is crowned by a chain of snow-capped mountains, separated by broad patches of lower ground.

Encyclopaedia Britannica, 11th Edition, Volume 14, Slice 2 |Various
Cuxton is at the entrance of the valley between the two chalk ranges of hills which form the water-parting of the river Medway.

A Week's Tramp in Dickens-Land |William R. Hughes
The zigzag line described is not a range of mountains, but a water-parting, which is quite another matter.

Fragments of Earth Lore |James Geikie
Our track led along the water-parting between the Ituri and Ihuru rivers.

In Darkest Africa, Vol. 1; or, The quest, rescue and retreat of Emin, governor of Equatoria |Henry Morton Stanley

The delimitation is thus a quite natural and scientific one, coinciding pretty closely to the water-parting of the two countries.

In the Border Country |W. S. (William Shillinglaw) Crockett

water parting

another term (esp US) for watershed (def. 1)