Water energy can be defined as the energy that is derived from water, generally through its motion. A common example of water energy is hydroelectricity, which derives power from the water that flows over dams. Another important example of water energy is the energy that is harnessed from the tides (also known as tidal energy). The kinetic energy of flowing water is often referred to as hydraulic energy. This hydraulic energy is converted into mechanical energy (for the movement of certain mechanical devices), and then into electrical energy (usually with the help of rotating turbines).
Typically, water energy is harnessed by making a large volume of water flow from a higher altitude to a lower altitude (the momentum gained by the water as a consequence of the gravitational forces acting on it is harnessed and converted into usable energy). Water energy is a clean, renewable source of energy.