Damming rivers can permanently alter river systems and wildlife habitats. A dam blocks fish migration, stops nutrients from flowing downstream, and changes water quality, all of which negatively impact the river ecosystem. The Iron Gates dams on the Danube River block important spawning sites and do not have fish passes, disrupting the migration and spawning of endangered sturgeon species.
2. About hydropower
The water behind the dam flows
through an intake and pushes
against blades in a turbine,
causing them to turn. The
turbine spins a generator to
produce electricity. The amount
of electricity that can be
generated depends on how far
the water drops and how much
water moves through the
system. The electricity can be
transported over long-distance
electric lines to homes,
factories, and businesses.
Hydropower (from hydro, meaning water) is energy that comes from the force of moving
water. The fall and movement of water is part of a continuous natural cycle called the
water cycle.
A typical hydro plant is a system with three parts: an electric plant where the electricity is
produced; a dam that can be opened or closed to control water flow; and a reservoir
where water can be stored.
3. About hydropower
Clean
and
renewabl
e energy
source
Hydropower is the cheapest way to generate
electricity today. That's because once a dam has
been built and the equipment installed, the energy
source—flowing water—is free.
It's a clean fuel source that is renewable yearly by
snow and rainfall.
Furthermore, hydro plants do not emit pollutants into
the air because they burn no fuel.
Hydropower is also readily available; engineers can
control the flow of water through the turbines to
produce electricity on demand. In addition,
reservoirs may offer recreational opportunities, such
as swimming and boating.
Hydropower plants produce power cheaply due to
their sturdy structures and simple equipment. Hydro
plants are dependable and long-lived, and their
maintenance costs are low compared to coal or
nuclear plants.
4. Summary of the Environmental Impacts of
Dams
Damming
rivers may
permanentl
y alter river
systems
and wildlife
habitats.
5. The impact of dams on river
ecosystems
Negative
effects
Negative environmental effects due to
construction activities
Loss of wild lands, wetlands and wildlife
habitat
Effects of stopping the flow of nutrients
downstream
Reduced biological activity downstream
Anaerobic decomposition of vegetation and
production of greenhouse gasses
Water-loss due to evaporation
Changes in water quality due to the lack of
dissolved oxygen near the bottom of
reservoirs. This is toxic to fish and can lead
to the death of aquatic life. It is also
corrosive to turbines.
6. The impact of dams on river
ecosystems
Negative
effects
Accomodation of amphibians, riparian
fauna and birds to a new environment
Migration of animals to new areas,
where new equilibrium may favour
some species over others
Blocking fish migration
Introducing of new species of fish in the
reservoirs
Inappropriate reservoir operation with
large variations in water levels could
threaten fish by drying up shallow-
breeding and flood producing areas.
7. The impact of dams on river
ecosystems
THE
PYRAMID
OF
IMPACTS
www.labond.com/Dams/...
8. The Iron Gates Dams and disruption
of
spawning migration of Danube
sturgeons
Sturgeons
are very
sensitive to
habitat
changes.
Altered
habitats
can
immediately
impact on
their
spawning,
wintering
and feeding
success,
and
ultimately
lead to their
extinction.
Iron Gates is the largest hydropower dam
and reservoir system along the entire
Danube. The system consists of two main
dams, Iron Gates I and II, built in 1972
and 1985 respectively. The dams are
constructed at river km 942 and river km
863 upstream of the Danube delta, in
effect confining migratory sturgeons to
863 km of the river and cutting off
important spawning sites in the Middle
Danube.
The Iron Gates dams do not have
technical equipment such as fish passes
or bypasses, designed to assist fish
