Behind me is a generator under repair. Water comes in via the pennstock into the scroll case (which I examined). It is then let in by opening wickets (like a venitian blind), and turns a wheel, which in turns rotates a shaft, which turns a set of magnets past a coil of windings. I am standing at the top of it all. The windings are just below, and underneath it all is the scrollcase. It was an intersting visit.