Environmental Engineering Reference
In-Depth Information
renewable resource that will be around for at least as long as humans. Hydropower is
controllable; that is, engineers can control the flow of water through the turbines to
produce electricity on demand. Finally, hydropower impoundment dams create huge
lake areas for recreation, irrigation of farm lands, reliable supplies of potable water,
and flood control.
Hydropower, though, also has some disadvantages; it is these disadvantages or
environmental impacts that have been the focus of this text. For example, fish popu-
lations can be impacted if fish cannot migrate upstream past impoundment dams to
spawning grounds or if they cannot migrate downstream to the ocean. Many dams
have installed fish ladders or elevators to aid upstream fish passage. Downstream
fish passage is aided by diverting fish from turbine intakes using screens or racks
or even underwater lights and sounds, and by maintaining a minimum spill flow
past the turbine. Hydropower can also impact water quality and flow. Hydropower
plants can cause low dissolved oxygen levels in the water, a problem that is harmful
to riparian habitats and is addressed using various aeration techniques that oxygen-
ate the water. Maintaining minimum flows of water downstream of a hydropower
installation is also critical for the survival of riparian habitats. Hydropower is also
susceptible to drought. When water is not available, the hydropower plants can-
not produce electricity. Typical activities during operation of a hydropower plant
include operation of the facility, power generation, and associated maintenance
activities that would require vehicular access and heavy equipment operation when
components are being replaced. Finally, construction of new hydropower facilities
impacts investors and others by competing with other uses of the land. Preserving
local flora and fauna and historical or cultural sites is often more highly valued than
electricity generation.
THOUGHT-PROVOKING QUESTIONS
4.1
A few environmentalist groups advocate tearing down existing hydroelec-
tric dams in the United States to allow affected rivers to run free. Do you
support or oppose this argument? Why?
4.2
Do we have any more water on Earth today than yesterday or 1000 years
ago?
4.3
According to the Rachel River account, the scientists and environmental
scientists devised several recommendations to alleviate the downward trend
in salmon population. What additional recommendations would you make
to mitigate the situation?
4.4
In the Rachel River account, what is the meaning of the statement: “Notice
they didn't try to ask the Native Americans. They also would have known
what to do. The salmon had already told them.”
4.5
Explain why an increase in water temperature affects salmon populations.
4.6
When you compare the pros and cons of hydroelectric power it sounds
great—so why don't we use it to produce all of our power?
4.7
Does the Rachel River account and the indicated mitigation procedures
indicate to you that science and scientists can solve all problems?
