Hydrostatic head

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As shown in this drawing, the hydrostatic head is the vertical distance between the water level in the reservoir and the turbine that is turned by the flowing water.

When generating hydropower, the head is a general term used to describe the distance that a given water source has to fall before the point where power is generated. Ultimately the force responsible for hydropower is gravity, so a hydroelectricity plant with a tall/high head can produce more energy than a similar plant with a short/low head. The difference is immediately apparent if you compare the Hoover Dam on the Colorado River between Nevada and Arizona with the Aswan Dam in Egypt. In short, a larger head allows water to fall a greater distance, which in turn allows more kinetic energy to accumulate. That energy is then harnessed by a water wheel or water turbine to create usable hydropower.

[edit] See also

• Hydraulic head for a more technical description of the physical principle of hydraulics

[edit] References

• U.S. Bureau of Reclamation: Glossary (See “Head”)
• U.S. Minerals Management Service: Glossary (See “Hydraulic head”]
• Society of Petrophysicists & Well Log Analysts: Glossary (See “Hydraulic head”)
• Keidel.com: “Pressure vs. Head”