bayou / perennial river

In the Roman civil law, it is laid down, that, to constitute a river or running stream, as contradistinguished from torrents and temporary water-courses, the flow of water must be perpetual; though, if a stream which usually runs throughout the year should happen to be dried up during summer, it would not cease to be perennial, any more than a stream which usually flows only during winter would be perennial because of an extraordinary flow during summer.