They're not full plans, but the following might give enough clues or hints to get you going.
Home Power has a series of articles that about what hydro power is.
The Green Optimistic has an article that demonstrates the general concept of building a microhydro device.
Practical Action has various brochures discussing micro-hydro power.
These are probably the most helpful links:
On Instructables, a user
made a micro-hydro device from CDs and another user
made a a larger microhydro system.
The general idea behind microhydro is to take running water, transfer that
energy into mechanical energy (spinning of the turbine), and then transfer the mechanical energy into something you find more useful, like electricity. And electricity isn't too hard, wrap copper wire around a magnet and you're pretty much ready to go.And if you want to go in reverse, just apply electricity to a magnet and copper setup.
