from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The line defining the lowest points along the length of a river bed or valley.
  • noun A subterranean stream.

from The Century Dictionary.

  • noun A line upon a topographical surface which is a natural watercourse, having everywhere the direction of greatest slope, and distinguished by having the lines of straight horizontal projection which cut it at right angles on the upper sides of the curves of equal elevation to which they are tangent.

from the GNU version of the Collaborative International Dictionary of English.

  • noun A line following the lowest part of a valley, whether under water or not.
  • noun The line of continuous maximum descent from any point on a land surface, or that cutting all contours and angles.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun geology, geography The line that connects the lowest points in a valley or river channel, and thus the line of fastest flow along a river’s course.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun the middle of the chief navigable channel of a waterway that forms the boundary line between states
  • noun a line following the lowest points of a valley


from The American Heritage® Dictionary of the English Language, 4th Edition

[German Talweg, Thalweg : 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).]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From 19th century German Thal ("valley") + Weg ("way, course")


  • For those of you who don't know, a thalweg is the last remnants of water where a fish can survive when the water has receded.

    The Vail Trail - All Sections

  • Apparently, the border was agreed as being the 'thalweg' middle of the deep water channel to you & me at Algiers in 1975 but once you are out of the mouth of the Shatt-al-Arab there is no thalweg anymore.

    Britannia Ruled the Waves

  • Davidson also taught the group a few new definitions, "thalweg" being the favorite.

    The Vail Trail - All Sections

  • The escarpment has been shaped into numerous irregularities, indentations, and promontories, and is pierced by thalweg ravines, gorges, and rocky passages connecting the plain and plateau.

    Cliffs of Bandiagara (Land of the Dogons), Mali

  • The line of maximum velocity or thalweg moves from side to side within a channel.


  • In this straight channel stream, bars form in the regions of the stream away from the thalweg.

    Fluvial landforms

  • In straight streams, bar-like deposits can form in response to the thalweg (red arrows in Figure 5) and helical flow.

    Fluvial landforms

  • Riffles, another type of coarse deposit, develop beneath the thalweg in locations where the faster flow moves vertically up in the channel.

    Fluvial landforms

  • The dates form a kind of square with a sharp triangle to the south, upon the left bank of the thalweg, which overflows them during floods.

    The Land of Midian

  • It has been abundantly supplied with water; in fact, the whole vein (thalweg) subtending the left bank would respond to tapping.

    The Land of Midian


Log in or sign up to get involved in the conversation. It's quick and easy.

  • subsurface, groundwater stream percolating beneath and in the general direction of a surface stream; lowest thread along the axial part of a valley.

    March 6, 2008

  • Came across this word while doing research for my memo on whether the public has any fishing/navigation rights for a Georgia stream that passes through the property of a private individual.

    March 24, 2008

  • "The main thrust of the river flow is known to hydrologists as the "thalweg"; it does not move in a straight and forward line but, mingling with the inner flow and the variegated flow of the surface and bottom waters, takes the form of a spiral or helix."

    Thames: The Biography by Peter Ackroyd, p 4

    August 11, 2009