thalweg

thal·weg  (tälvg)

n. Geology

1. The line defining the lowest points along the length of a river bed or valley.

2. A subterranean stream.

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[German : Tal, Thal, valley (from Middle High German tal, from Old High German) + Weg, way (from Middle High German wec, weg, from Old High German weg; see wegh- in Indo-European roots).]

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thalweg  (tälvg)

1. The line defining the lowest points along the length of a river bed or valley, whether underwater or not.

2. A subterranean stream following a course similar to that of an overlying surficial stream.

Thesaurus

Noun	1.	thalweg - the middle of the chief navigable channel of a waterway that forms the boundary line between states bound, boundary, edge - a line determining the limits of an area
	2.	thalweg - a line following the lowest points of a valley contour, contour line - a line drawn on a map connecting points of equal height