ADVANTAGES TO HYDROELECTRIC POWER:
- Fuel is not burned so there is minimal pollution
- Water to run the power plant is provided free by nature
- It's renewable - rainfall renews the water in the reservoir, so
the fuel is almost always there
- Comparison with other methods of power generation
- Hydroelectricity eliminates the flue gas emissions from fossil
fuel combustion, including pollutants such as sulfur dioxide,
nitric oxide, carbon monoxide, dust, and mercury in the coal.
- Compared to the nuclear power plant, hydroelectricity generates
no nuclear waste, nor nuclear leaks. Unlike uranium,
hydroelectricity is also a renewable energy source.
- Compared to wind farms, hydroelectricity power plants have a
more predictable load factor. If the project has a storage
reservoir, it can be dispatched to generate power when needed.
Hydroelectric plants can be easily regulated to follow variations
in power demand.
- Unlike fossil-fueled combustion turbines, construction of a
hydroelectric plant requires a long lead-time for site studies,
hydrological studies, and environmental impact assessment.
Hydrological data up to 50 years or more is usually required to
determine the best sites and operating regimes for a large
- Unlike plants operated by fuel, such as fossil or nuclear
energy, the number of sites that can be economically developed for
hydroelectric production is limited; in many areas the most cost
effective sites have already been exploited.
- New hydro sites tend to be far from population centers and
require extensive transmission lines. Hydroelectric generation
depends on rainfall in the watershed, and may be significantly
reduced in years of low rainfall or snowmelt. Long-term energy
yield may be affected by climate change. Utilities that primarily
use hydroelectric power may spend additional capital to build extra
capacity to ensure sufficient power is available in low water
DISADVANTIAGES TO HYDROELECTRIC POWER
- Recreational users must exercise extreme care when near
hydroelectric dams, power plant intakes and spillways.
- Warning on embankment about sudden water release
- Hydroelectric projects can be disruptive to surrounding aquatic
ecosystems. For instance, studies have shown that dams along the
Atlantic and Pacific coasts of North America have reduced salmon
populations by preventing access to spawning grounds upstream, even
though most dams in salmon habitat have fish ladders installed.
Salmon spawn is also harmed on their migration to sea when they
must pass through turbines. This has led to some areas transporting
smolt downstream by barge during parts of the year. Turbine and
power plant designs that are easier on aquatic life are an active
area of research.
- Generation of hydroelectric power changes the downstream river
environment. Water exiting a turbine usually contains very little
suspended sediment, which can lead to scouring of riverbeds and
loss of riverbanks. Since turbines 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 may change from
pre-construction conditions. Water exiting from turbines is
typically much colder than the pre-dam water, which can change
aquatic faunal populations, including endangered species. Some
hydroelectric projects also utilize canals, typically to divert a
river at a shallower gradient to increase the head of the scheme.
In some cases, the entire river may be diverted leaving a dry
riverbed. Examples include the Tekapo and Pukaki Rivers.
- Large-scale hydroelectric dams, such as the Aswan Dam and the
Three Gorges Dam, have created environmental problems both upstream
- A further concern is the impact of major schemes on birds.
Since damming and redirecting the waters of the Platte River in
Nebraska for agricultural and energy use, many native and migratory
birds such as the Piping Plover and Sandhill Crane have become
GREENHOUSE GAS EMISSIONS
- The reservoirs of hydroelectric power plants in tropical
regions may produce substantial amounts of methane and carbon
dioxide. This is due to plant material in flooded areas decaying in
an anaerobic environment, and forming methane, a very potent
greenhouse gas. According to the World Commission on Dams report,
where the reservoir is large compared to the generating capacity
(less than 100 watts per square meter of surface area) and no
clearing of the forests in the area was undertaken prior to
impoundment of the reservoir, greenhouse gas emissions from the
reservoir may be higher than those of a conventional oil-fired
thermal generation plant.
- In boreal reservoirs of Canada and Northern Europe, however,
greenhouse gas emissions are typically only 2 to 8% of any kind of
conventional fossil-fuel thermal generation. A new class of
underwater logging operation that targets drowned forests can
mitigate the effect of forest decay.
- Another disadvantage of hydroelectric dams is the need to
relocate the people living where the reservoirs are planned. In
many cases, no amount of compensation can replace ancestral and
cultural attachments to places that have spiritual value to the
displaced population. Additionally, historically and culturally
important sites can be flooded and lost. Such problems have arisen
at the Three Gorges Dam project in China, the Clyde Dam in New
Zealand and the Ilısu Dam in Southeastern Turkey.
- Failures of large dams, while rare, are potentially serious -
the Banqiao Dam failure in Southern China resulted in the deaths of
171,000 people and left millions homeless. Dams may be subject to
enemy bombardment during wartime, sabotage and terrorism. Smaller
dams and micro hydro facilities are less vulnerable to these
- The creation of a dam in a geologically inappropriate location
may cause disasters like the one of the Vajont Dam in Italy, where
almost 2000 people died, in 1963.
Submitted by Pat Babcock, NGC Energy Conservation