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A
The line connecting the lowest points along the entire length of a river valley — the natural channel of deepest water.
— Geography reference
B
From the German Tal (valley) and Weg (way or path) — literally the valley path, referring to the natural course water takes through a valley.
— German etymology
C
In international law, the thalweg is frequently used as the boundary between two nations when a river forms the border, as it represents a natural midpoint.
— International law
D
Because rivers migrate over time, thalweg-based borders can shift gradually, creating recurring disputes between nations over river boundaries.
— Border law review
E
The term was first used in international boundary law in the 1814 Treaty of Paris, which used it to demarcate the Franco-German border along the Rhine.
— Treaty of Paris commentary