Legal Definitions - live thalweg

Definition: Live thalweg refers to the part of a river channel that is most followed, usually at the middle of the principal channel. Thalweg, on the other hand, is a line following the lowest part of a valley or the middle of the primary navigable channel of a waterway, constituting the boundary between states.

Example: In the case of Louisiana v. Mississippi, the Supreme Court defined the live thalweg as the part of the river channel that is most followed by the water. This means that the boundary between the two states is determined by the middle of the primary navigable channel of the river.

Explanation: The example illustrates how the live thalweg is used to determine the boundary between states. In this case, the Supreme Court used the live thalweg to settle a dispute between Louisiana and Mississippi over the ownership of an island in the Mississippi River. By following the most navigable part of the river channel, the court was able to determine which state had jurisdiction over the island.