ˈtälˌveg, -vāḵ noun
( -s )
Etymology: German talweg (formerly spelled thalweg ), from tal valley (from Old High German) + weg way, path, from Old High German — more at dale , way
1.
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 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