Geography Reference
In-Depth Information
Hydroelectric power
Hydroelectric power
(HEP) utilizes the movement of water on Earth's surface to produce electricity.
It is most often associated with a dam that is built across a fairly narrow valley, causing a river that
runs through it to back up on the upstream side. Eventually, a reservoir rises to nearly the height of
the dam (see Figure 16-6). Intake vents near the lake's surface admit water that falls within large con-
duits, ultimately to strike turbine blades, which causes them to rotate at high speed and operate an
electrical generator. HEP may be considered perennial because as long as the sun shines (practically
eternity), water will be evaporated, fall to Earth as precipitation, collect in rivers, and be available for
power production.
Figure 16-6:
Dams may pro-
duce hydro-elec-
tric power while
promoting flood
control, irrigation,
recreation, and
drinking
water
supply.
HEP supplies about a quarter of the world's electricity. Not only is it a non-polluting energy source
(nothing is burned), but the reservoirs may provide recreational opportunity, flood control, and water
for people and agriculture. In addition, HEP projects may have important symbolic value. For ex-
ample, China is presently engaged in construction of the giant Three Gorges Dam on the Yangtze
River. While the finished project will provide all of the benefits noted previously, the dam is perhaps
even more important (to the Chinese at least) as a symbol of the nation's emergence as a major world
power and of the government's ability to accomplish great deeds.
Onthe negative side, construction ofHEP projects is expensive. Many millions (even billions) ofdol-
lars may be required before the first bit of electricity is produced. Indeed, this is doubly bad because
the areas of greatest hydroelectric power potential includes countries in Africa and Southeast Asia
that do not have the financial wherewithal to fund such projects.
HEP development has additional geographical constraints. Obviously, you can't build a dam just any-
where. You need a river valley, and especially a narrow one for the simple reason that building across
a narrow valley is cheaper than building across a wide one. Also, the eventual reservoir-related flood-
