The pumping of water from a lower to higher elevation to store energy (potential). Discharge works much like a hydroelectric dam.
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Blenheim-Gilboa Pumped Storage Power Project
New York Power Authority facility generates one million kilowatts in the Catskill mountains using five billion gallons of water and a 2,000 foot elevation
WikiPedia Entry on subject lists projects and shows a diagram of a typical station. Power spectrum diagram shows energy in and out.
TVA: Hydroelectric Power
Answers question: "What is a pumped-storage plant?" with links to a diagram and a picture.