So, this has only happened to me once, and I am fairly sure it is unintended but when I spawn tsunamis in an area while having my mouse go everywhere, sometimes there will be water pollution sources. I have only had this happen in the Map Editor. They just spawn polluted water and kinda sit there. It is annoying in the sense you cant control them, but nice because you can see the dynamic flow of water. Would be nice if you could create this as an actual feature or remove it entirley, or create a seperate mod for it.

As a side note I have not checked if they corrupt save files or stuff like that.