Gene,
Here is a thought for you. This will sound nuts, but it could work. Bachmann makes a water pump. You could makes an upper and lower pond out of a plastic reservoir of some sort, tupperware?, and use the WS special water effects to make a falls between the two. Then the pump could transfer the water from lower to upper pond.
I kid you not. A few years back some company that escapes my mind right now made an HO scale sawmill that had this principle in it. The water was pumped up from the mill pond through a "mountain" to run out through a mill stream to the water wheel and down to the pond again. It was cool then...why not now?
I'll search and if I find the old kit I'll post it.
B-) & :x