Geog. [Ger. thalweg bottom path of a valley, f. thal valley (see DALE) + weg WAY. Also in Fr. (1815 Traité de Paris, Littré).] The line in the bottom of a valley in which the slopes of the two sides meet, and which forms a natural watercourse; also the line following the deepest part of the bed or channel of a river or lake.
1862. Wraxall, Hugo’s Misérables, V. xxii. The grand sewer running along the thalweg of the valley.
1881. Harper’s Mag., LXIV. 275. Thalweg … is a German geographical term, employed in the records of the congress of Berlin, which designates the line of lowest level formed by the two opposite slopes of a valley.
1894. (May 12) Agreemt. betw. Gt. Brit. & Congo State, in Parl. Papers Eng., XCVI. 26. Thence it [the boundary] shall follow the ‘thalweg’ of the Nile southwards to Lake Albert.
1897. Educat. Rev., XIII. 89. This thalweg which forms a nearly continuous water way from the Volga to the Amur.
