Hydraulic energy has been known for a very long time. It was the source of energy for watermills, which provided mechanical energy to grind grain or to draw water. Today, hydraulic energy is mainly used to produce electricity in hydroelectric power stations, by making use of the energy of waterfalls. Falling water (a significant change in potential energy) contains energy in a much more concentrated state than the water flowing in a river (kinetic energy).
Hydraulic energy is an indirect consequence of solar energy, like a lot of energy sources on earth (the wind, the ocean swell, the biomass, fossil energy …). The sun causes the ocean water to evaporate and the clouds move with the wind. Temperature reductions over continental landmasses cause condensation of the water vapour and the resulting rain and snow supply water to rivers and lakes.
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