(The following text is derived from the United States Department of Energy's description of Microhydropower Technology.)
"Hydropower systems use the energy in flowing water to produce electricity or mechanical energy. Although there are several ways to harness the moving water to produce energy, run-of-the-river systems, which do not require large storage reservoirs, are often used for microhydropower systems.
For run-of-the-river microhydropower systems, a portion of a river's water is diverted to a water conveyance—channel, pipeline, or pressurized pipeline (penstock)—that delivers it to a turbine or waterwheel. The moving water rotates the wheel or turbine, which spins a shaft. The motion of the shaft can be used for mechanical processes, such as pumping water, or it can be used to power an alternator or generator to generate electricity.
A microhydropower system can be connected to an electric distribution system (grid-connected), or it can stand alone (off-grid)."
- ↑ 1.0 1.1
"DOE-EERE: Microhydropower System"