From English - German Ding/FreeDict dictionary ver. 1.9-fd1:
tributary stream /tɹˈɪbjuːtəɹi stɹˈiːm/
Nebenfluss <masc>, Zufluss <masc>, Zubringer <masc> [geogr.]
Note: eines größeren Fließgewässers
Synonyms: side river, side stream, tributary river, tributary, feeder stream, feeder, affluent, influent
see: side rivers, side streams, tributary rivers, tributary streams, tributaries, feeder streams, feeders, affluents, influents