[ tahl-veg, -veyk ]
/ ˈtɑl vɛg, -veɪk /


a line, as drawn on a map, connecting the lowest points of a valley.
Chiefly International Law. the middle of the main navigable channel of a waterway that serves as a boundary line between states.

Origin of thalweg

1860–65; < German, equivalent to Thal, now obsolete spelling of Tal valley (cognate with dale) + Weg way1 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for thalweg

  • The thalweg has been frequently confirmed as the accepted boundary where no conventions to the contrary existed.

    International Law|George Grafton Wilson and George Fox Tucker

British Dictionary definitions for thalweg



/ (ˈtɑːlvɛɡ) /

noun geography rare

the longitudinal outline of a riverbed from source to mouth
the line of steepest descent from any point on the land surface

Word Origin for thalweg

C19: from German, from Thal valley + Weg way, path
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for thalweg



1831, from German Thalweg "path along the bottom of a valley," from thal (see dale) + weg (see way).

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for thalweg


[ tälvĕg′ ]

The line defining the lowest points along the length of a river bed or valley, whether underwater or not.
A subterranean stream following a course similar to that of an overlying surficial stream.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.