Watercourse

"A watercourse is the channel that a flowing body of water follows.

In the UK, some aspects of criminal law, such as the Rivers (Prevention of Pollution) Act 1951, specify that a watercourse includes those rivers which are dry for part of the year.

In some jurisdictions, owners of land over which the water flows may have rights to some or much of the water in a legal sense. These include estuaries, rivers, streams, anabranches and canals. If it is navigable, it is also a "waterway"." - (en.wikipedia.org 23.07.2021)