thal·​weg | \ ˈtälˌveg, -vāḵ \
plural -s

Definition of thalweg

1a : 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 one crossing all contour lines at right angles
c : subsurface water percolating beneath and in the same direction as a surface stream course
2 : the middle of the chief navigable channel of a waterway which constitutes a boundary line between states

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History and Etymology for thalweg

German talweg (formerly spelled thalweg), from tal valley (from Old High German) + weg way, path, from Old High German

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Cite this Entry

“Thalweg.” Dictionary, Merriam-Webster, Accessed 3 Jul. 2020.

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