I was messing around in dev mode on a river map. I modified the terrain so that the river forked around my base. After adding "Shallow moving water" and "Chest Deep moving water", I noticed that there is some barrier that is generated when the map is created that prevents the water flowing animation from following up the newly created river. It would be cool if we could do away with that if possible.
(http://bit.ly/2PFzI84)
Not possible to do in normal gameplay, so this isn't really a bug. We make no attempt to support every thing that's possible with dev tools, just things possible in play. Thanks for reporting anyway.