[tahl-veg, -veyk]


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

Historical Examples of 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



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



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.