Water wheel?

Has anyone built a water wheel rather than a waterfall? I was trying to
dream up ways to hide my filter barrels (wip) without taking up too much
room. So I thought if I built a narrow mill house beside the pond, I could
hang a water wheel over the pond and save myself some space. The one problem
I foresee is that the water required to turn the wheel (3') will be far less
than the filter outputs. I'll need to split the filter output and channel
most of the water straight back into the pond.

Has anyone built one? Any design/material tips? I'd like it to be fairly
light, since I won't have a support post on the outside of the wheel. I was
thinking I could use the weight of the barrels to counterbalance the wheel.
Of course cleaning the barrels might present a problem. I've seen a few
built out of plywood, but I don't imagine they would hold up to water that
well.

Any tips appreciated.