Leonardo da Vinci designed water-wheel machines to convert flowing water into useful mechanical power.
A water wheel captures the energy of moving or falling water and transfers it through a rotating shaft. Leonardo studied wheels, paddles, channels, and gearing as parts of larger systems for lifting water, grinding materials, or driving machinery. His notebooks contain detailed observations of water flow and mechanical transmission.
Leonardo did not invent the water wheel. Water-powered wheels had been used for centuries before him, especially in mills. His contribution was to analyze and redesign hydraulic machinery with unusually careful drawings and experiments. This is an important distinction from claims that he invented every machine he sketched.
His water studies also influenced designs for pumps, canals, locks, and other hydraulic devices. The basic energy conversion remains familiar today: a fluid's motion turns a wheel or turbine, and that rotation can perform work. Modern hydroelectric plants use turbines and generators rather than traditional wooden mill wheels.