Water Power: Supplying Our Electric Needs
The use of natural water supplies to produce power has been used
for thousands of years. However, the specific use of dams to
harness the energy of significant river systems still causes
debate. The National Garden Clubs does not take an official view on
the use, or non use, of dams to create hydroelectric power.
However, we believe that a well educated membership is a strength
of our organization, and we offer this information as part of our
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
disadvantages to hydroelectric power:
- Recreational users must exercise extreme care when near
hydroelectric dams, power plant intakes and spillways.
- There is a risk of sudden water release.
- Hydroelectric projects can be disruptive to surrounding aquatic
ecosystems. 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
- The 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
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. For
example, 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 threats. 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
For more information, contact:
Robertson Overton, NGC Energy Conservation Chairman