I've just read "The October Man", the Rivers of London novella set in Germany with German characters, and Morgane, the baby goddess of the Mosel, is emphatic in pointing out she speaks "French, German, and Luxemburgish" - so clearly multiculturalism is something that comes automatically with being a river that contacts many places.

There's even the Spirit of the Grand Union Canal in one of the stories in the collection Tales from the Folly (Tyburn is emphatic she doesn't count as a goddess, but that's Ty being Ty).