I would be fine with waterway=waterfall + man_made=yes + description=blahblah. Maybe add that description to the fountain node as well, unless there is clearly also a fountain part that shoots water up.

My counter suggestion, upon reflection, would be man_made=waterfall + description=blahblah, and maybe turning the current fountain node into an area covering the water and cascade, and having that description there as well. A fountain is generally a man-made water feature, and this seems to be that, only in the shape of a waterfall/cascade - which we can show with the man_made=waterfall node.

But I would be fine with either and open to other suggestions if anyone has thoughts.

(And a note, legally we are not allowed to use Google data or images as sources for editing due to copyright. Services are Mapillary are appropriately licensed, but this was the closest angle I could find on it: https://www.mapillary.com/map/im/B_ftFqJ9eWcNkW2VWCbe7A )