Moisture percolating into the soil may become ground water (subsurface water), some of which
also enters water bodies through springs or underground streams.
Ground water may move
upward through soil during dry periods and may return to the atmosphere by evaporation.
Water vapor passes into the atmosphere by evaporation then circulates, condenses into clouds,
and some returns to earth as precipitation. Thus, the water cycle is complete. Nature ensures
that water is a renewable resource.
Generating Power
In nature, energy cannot be created or destroyed, but its form can change.
In generating
electricity, no new energy is created. Actually one form of energy is converted to another form.
To generate electricity, water must be in motion. This is kinetic (moving) energy. When
flowing water turns blades in a turbine, the form is changed to mechanical (machine) energy.
The turbine turns the generator rotor which then converts this mechanical energy into another
energy form -- electricity. Since water is the initial source of energy,
we call this hydroelectric
power or hydropower for short.
At facilities called hydroelectric powerplants, hydropower is generated. Some powerplants are
located on rivers, streams, and canals, but
for a reliable water supply, dams are needed. Dams
store water for later release for such purposes as irrigation, domestic and industrial use, and
power generation. The reservoir acts much like a battery, storing water to be released as needed
to generate power.
The
dam creates a
A
head
@
or height from which water flows. A pipe (penstock) carries the water
from the reservoir to the turbine. The fast-moving water pushes the turbine blades, something
like a pinwheel in the wind. The waters force on the turbine blades turns the rotor,
the moving
part of the electric generator. When coils of wire on the rotor sweep past the generator
=
s
stationary coil (stator), electricity is produced.
This concept was discovered by Michael Faraday in 1831 when he found that electricity could be
generated by rotating magnets within copper coils.
When the water has completed its task, it flows on unchanged to serve other needs.
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