A water power engine includes prime movers driven by water and which may be classified under three categories:
Hydro power is generated when the natural force from the water's current moves a device (fan, propeller, wheel) that is pushed by the force of the water. Ordinary water weighs 8.36 lbs per gallon (1 kg per liter). The force makes the turbine mechanism spin, creating electricity. As long as there is flow, it is possible to produce electricity. The advantage of electricity generated in this way is that it is a renewable resource. A small-scale Micro Hydro Power can be a long lasting piece of technology. The problem of the system is that technology has yet to be developed more than what it is today.