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creek: a small stream that flows in a surface depression.
condensation: the change of state from water vapor to liquid water.
dam: a concrete barrier constructed across a river and designed to control water flow and create a reservoir.
electrical energy: energy resulting from the flow of charged particles, such as electrons or ions
electric generator: a device that converts mechanical energy to electrical energy, usually by rotating a conductor in a magnet field.
evaporation: the change of state from liquid water to a water vapor.
falling-water system: hydroelectric power plant that operates on available water flow in a channel or pipe through the use of gravity.
groundwater: water that enters and is stored in the ground.
head: The vertical height of water in a reservoir above the turbine.
hydroelectric energy (hydroelectricity): electrical power derived from the flow of water on Earth's surface.
hydroelectric power plant: facility that produces electricity through the use of flowing water in streams and rivers.
kinetic energy: a form of energy associated with motion of a body of matter.
mechanical energy: the sum of the kinetic energy and the potential energy of a body of matter.
penstock: a pipe or canal through which water passes from a reservoir or river to a power-producing turbine.
precipitation: any form of water the falls from the atmosphere to the Earth's surface, such as rain, snow, sleet, and hail.
reservoir (1): a body of water collected and stored in an artificial lake behind a dam.
reservoir (2): a place in the water cycle that holds water.
river: a relatively large flow of water in a natural channel.
runoff: water that flows over the ground and reaches a stream as a result of rainfall or snowmelt.
run-of-the-river system: hydroelectric power plant that operates on available water flow from a stream or river.
stream: a small or large flow of water in natural channels.
tributary: a stream that converges with another stream and contributes water.
turbine: a rotating device that converts the kinetic energy from moving water into mechanical energy which is then used to produce electricity.
water cycle (hydrologic cycle): the continuous circulation of water through the hydrosphere as solid, liquid, or gas. The hydrosphere flows through each of Earth's major systems.