On a mountain slope close to Volskygge I suddenly have http://i.imgur.com/NzSLb1d.jpg, which I haven't had in any previous play throughs. Does anyone have an idea which mod it might be that adds it - or how to check it with TES5Edit or something similar? I thought it might be a glitch, but it's there also after quitting and reloading the save.

When you took that picture did you go up there and check if there were a waterfall? Why I ask is simple because I do not recall seeing a waterfall there and I think you saw *windy* snow kind of a snowstorm.

Anyway, I could be wrong though and if I'm then I've no idea there is a waterfall in the same spot shown on the picture.

Yes, it is some kind of waterfall. My char got "svcked in" as in a stream when getting closeby, but she didn't get wet. And no, the "waterfall" is completely off - it shouldn't be there.

Open the console and select it, the first two characters of the form ID will tell you what plugin is responsible for it.