Bill, it's possible to do, but you may have a problem to generate enough power, with a wide micro turbine about 3', using light graphite, and a good generating coil. The problem is, if there's any break in flow due to poor flow condition, even though you have the head, your turbine will not be able to re-initiate the rotation because the coil generator tension. You can manipulate all you want on paper and come up with varying scenarios, but when you put into real application, well, let's just say you'll get an awaken call.
The hydro-electric dams around here are always have close to twice the head pressure going through the turbine rating because of that possible scenario. Some will just stick with the 1-to-1 (flow pressure to generator tension for re-initiation) because they have people monitoring it, with a nice capacitor of reserved power to help the coil generator to move along if it happens to just stop due to poor flow. How about combination of solar and mini-hydro, or better yet, wind turbine with gear drive to help the hydro turbine to flow when it stops (a direct drive effects), and when there's sufficient head and water to keep the water turbine going, the wind turbine will just free spin until it's needed again. A new invention in the works?
