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The Greening of IT
258 How Companies Can Make a Difference for the Environment

Related Activities
Reservoirs created by hydroelectric schemes often provide facilities
for water sports and become tourist attractions in themselves. In some
countries, farming fish in the reservoirs is common. Multi-use dams
installed for irrigation can support the fish farm with relatively constant
water supply. Large hydro dams can control floods, which would other-
wise affect people living downstream of the project. When dams create
large reservoirs and eliminate rapids, boats may be used to improve
transportation.

Disadvantages
Recreational users must exercise extreme care when near hydroelectric
dams, power plant intakes, and spillways.

Environmental Damage
Hydroelectric projects can be disruptive to surrounding aquatic
ecosystems both upstream and downstream of the plant site. For
instance, studies have shown that dams along the Atlantic and Pacific
ptg
coasts of North America have reduced salmon populations by preventing
access to spawning grounds upstream, even though most dams in a
salmon habitat have fish ladders installed. Salmon spawn are also
harmed on their migration to sea when they must pass through turbines.
This has led to some areas transporting smolt downstream by barge dur-
ing parts of the year. In some cases, dams have been demolished, (for
example, the Marmot Dam was demolished in 2007) because of the
impact on fish. Turbine and power-plant designs that are easier on
aquatic life are an active area of research. Mitigation measures such as
fish ladders might be required at new projects or as a condition of reli-
censing of existing projects.
Generation of hydroelectric power changes the downstream river
environment. Water exiting a turbine usually contains little suspended
sediment, which can lead to scouring of river beds and loss of river-
banks. Because turbine gates are often opened intermittently, rapid or
even daily fluctuations in river flow are observed. For example, in the
Grand Canyon, the daily cyclic flow variation caused by Glen Canyon
Dam was found to be contributing to erosion of sand bars. Dissolved
oxygen content of the water might change from preconstruction condi-
tions. Depending on the location, water exiting from turbines is