After going past the fantasy stage in thinking about this, I remembered there's no outlets outside on this old house at all. ...and do I want to pay to run electricity for something like this even if it was inside? No.
Although I would extremely enjoy any anecdotes or pics anyone has to share with an electric feature, I would be especially interested to hear about any experiences with solar water features. Looks like pumps start at about $20 for something that would only work when it's sunny, on up in price to something that also has batteries (recharged by solar also) to run 24 hrs.
My brief research so far has led me to understand that when there's a raise in a pumped water system, there is more water needed for it to function properly and the water all falls to the lowest level when the pump stops. Depending on the design, that could mean that some/a lot of the water overflows and is lost and, if not replaced before the pump starts back up, could leave so little water that the pump burns out. So a waterfall may be a stretch of what's possible... A little trickle over slightly raised rocks would probably be much more practical, although I don't think any rise is necessary to make a wheel turn, that's the part I really want.
