Thalweg (pronEng|ˈtɑːlvɛg [OED] ; an English word compounded from the German elements "Thal" (since Duden's orthography reform of 1901 written "Tal") meaning "valley", and "Weg", meaning "way") is a term adopted into English usage for geography and geomorphology. It signifies the deepest continuous line along a valley or watercourse.

In hydrology, the thalweg (sometimes called the "valley line") is a line drawn to join the lowest points along the entire length of a streambed or valley in its downward slope, defining its deepest channel. It thus marks the natural direction (the profile) of a watercourse. The thalweg is almost always the line of fastest flow in any river. The term is also sometimes used to refer to a subterranean stream that percolates under the surface and in the same general direction as the surface stream.

In geomorphology, the thalweg is the continuous line that follows the path of maximum slope or descent between two points. As such, it is at right angles to all contour lines. This definition encompasses the line connecting the lowest points along the valley floor or bed of a stream.

The thalweg principle is the principle which defines the border between two states separated by a watercourse as lying along the thalweg. The precise drawing of river borders has been important on countless occasions; notable examples include the Shatt al-Arab (known as Arvand Rud in Iran) between Iraq and Iran, the Danube in central Europe, the Kasikili/Sedudu Island dispute between Namibia and Botswana, settled by the International Court of Justice in 1999. [] and the 2004 dispute settlement under the UN Law of the Sea concerning the offshore boundary between Guyana and Surinam, South America, in which the thalweg of the Corentyne River played a role in the ruling.


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  • thalweg — 1831, from Ger. Thalweg path along the bottom of a valley, from thal (see DALE (Cf. dale)) + weg (see WAY (Cf. way)) …   Etymology dictionary

  • Thalweg — Thal weg , n. [G., fr. thal valley + weg way. See {Dale}; {Way}.] (Physiography) (a) A line following the lowest part of a valley, whether under water or not. (b) The line of continuous maximum descent from any point on a land surface, or that… …   The Collaborative International Dictionary of English

  • Thalweg — Thalweg, der stärkste u. tiefste Stromstrich in einem Fluß, wo stets das Fahrwasser ist …   Pierer's Universal-Lexikon

  • thalweg — talweg [ talvɛg ] n. m. VAR. thalweg • 1812; thalweg XVIIe; mot all., de Tal, (vx) Thal « vallée » et Weg « chemin » ♦ Géogr. Ligne de fond d une vallée. Dans une vallée drainée, le talweg est le lit du cours d eau. talweg ou thalweg n …   Encyclopédie Universelle

  • thalweg — (tal vègh ) s. m. Ligne plus ou moins sinueuse au fond d une vallée, suivant laquelle se dirigent les eaux courantes.    Thalweg d une vallée, la ligne d intersection des plans de pente latérale des deux berges de la vallée.    Thalweg d un cours …   Dictionnaire de la Langue Française d'Émile Littré

  • Thalweg — Talweg Pour les articles homonymes, voir Talweg (homonymie). Un talweg (ou thalweg) correspond à la ligne qui rejoint les points les plus bas d une vallée[1]. Sommaire 1 Talweg …   Wikipédia en Français

  • thalweg — ► sustantivo masculino Línea del mayor declive de un valle por la cual van las aguas corrientes cuando existen. IRREG. plural thalweg tb:tálveg * * * (voz alemana) ► masculino Vaguada …   Enciclopedia Universal

  • thalweg — /talveyk/ Old German spelling of Talweg, which title see. Under the doctrine of thalweg, the water boundary between states is defined as the middle of the deepest or most navigable channel, as distinguished from the geographic center or a line… …   Black's law dictionary

  • THALWEG — n. m. T. de Géographie Ligne de plus grande pente, suivant le fond d’une vallée, d’un vallon, d’un ravin …   Dictionnaire de l'Academie Francaise, 8eme edition (1935)

  • thalweg — 1) the river centre, the part with the greatest flow and depth. Used to define international riverine borders 2) the lowest thread along the axial part of a valley or stream channel 3) a subsurface, ground water stream percolating beneath and in… …   Dictionary of ichthyology

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