Here’s a post by Marie Brennan at Book View Cafe: New Worlds: Rivers
Rivers in Rokugan do not join together. They separate. That lake in the northeast: okay, it flows down from the mountains, but then . . . does it split? Or is that western branch flowing eastward to the sea, joining up with the eastern branch (which apparently flows through a small mountain range?), only then you have to assume that the major river running from northwest to southeast is the one that splits — just like the one due south of the mountains, down near the coast — or the lake in the eastern edge of the mountains, that somehow both flows north through the mountains and south to the sea — and the tiny little river along the coast that inexplicably has enough flow to form both a substantial bay and split off to form the biggest delta in the Empire — and let’s not even talk about what’s happening in that big patch of mountains at the very bottom of the map. It’s the setting’s equivalent of Mordor; we’ll just chalk it up to evil magic and move on.
I do spend some time gazing at maps and making sure rivers flow downhill! But I have never drawn a landmass that was actually based on a real landmass and put rivers in what were definitely the right spots … wait, I did do that once. I started with a map of Borneo. (Unpublished, so if you can’t think which book that is, that would be why.)
But usually I just draw the map and throw some mountains in there. And then put in rivers that I presume do flow consistently downhill. This is a really fun example that Brennan uses to illustrate how not to situate rivers, but you know what? It also makes me want to do a map where Evil Magic makes rivers flow uphill in some region. That would be entertaining!
Which Brennan recognizes:
However, if you do that, you have to do that. Make it clear to the reader that this is a setting where the normal laws of nature do not apply: rivers diverge instead of converging (and don’t become smaller as a result), water flows uphill in its determination to cross a mountain range, etc.
True! You should definitely at least mention that magic was involved. I’ve done that, though not for rivers specifically. I trust no one came away from WINTER OF ICE AND IRON with the idea that I thought a northern desert made geographical sense. Several times a character mentioned that this desert was created via a magical disaster.
Now I want to create a world where a river flows uphill in its determination to cross a mountain range. Would that be a river spirit? A river dragon? … I just realized I could work that in to my current WIP — not a spirit or dragon, but the interaction of the different layers of the world. Hmm. Don’t know that I’ll find reason to do that, but I sure could.
You know, one hard SF story that has a water element I don’t understand is Kirstein’s Steerswoman series. I don’t get how the “dolphin stairs” can possibly work. I mean … how do the dolphins get back up to the top? Have any of you who’ve read the series got a clear idea of how that works?