2. What is hydroelectricity and how
is it made?
Hydroelectric dams are conveniently placed in flowing
rivers. They allow a small amount of water flow
through a small tube and the pressure turns a turbine
which is connected to a magnet. Whenever you move a
magnet past a conductor it makes electricity flow. The
turbines turn which makes the connected magnet
moved around in the middle of a huge coil of copper
wire which transports the electricity to a battery,
which is connected to the city or village nearby.
3. About hydroelectricity
The process makes no direct pollution and hardly any
greenhouse gasses.
Hydroelectricity is produced in around 150 countries
with China producing more than any other.
It produces 16% of the worlds electricity
Half of the worlds big rivers have been dammed in at
least one place.
4. Flooding villages and cities
The construction of hydroelectric dams may lead to an
overflow and a flood in the reservoir, This can flood cities
and villages.
The 400 mile long reservoir of the Three Gorges Dam has
flooded 13 cities, 140 towns, 1352 villages, and 100,000 acres
of China’s most fertile farm land. The agriculture areas
along the river have produced nearly half the countries
total crop production. The farm land lost had provided
40% of China’s grain and 70% of rice crops Farmers that
were relocated to the hillsides of the dam have struggled to
grow crops, and so far the only viable crop able to be
produced on such steep terrain has been oranges. A total of
1.2 million people were relocated.
5. Earthquakes caused by dams
There are small gaps between tectonic plates and when they
press against each other they cause earthquakes, there also are
fault lines which are cracks in the earth. These are caused when
pressure is applied on one area of land, it pushes down and
around it pushes back up and damages the land, it pushes up
against other land, this is called a fault zone. This is just like the
way tectonic plates push up against each other and this can cause
an earthquake. The weight from reservoirs sometimes does this.
The Hoover Dam has caused earthquakes by doing this.
The most serious case may be the 7.9-magnitude Sichuan
earthquake in May 2008, which killed an estimated 80,000
people and has been thought to have been caused by the
construction of Zipingpu Dam.
fault zones
6. Plants and fish
The sediment gets stopped on side of the dam and
does not go through and without it plant life cannot
grow and without seaweed the fish cannot eat.
It disrupts migration because the fish such as salmon
migrate a lot but they can’t get past with the dam
blocking the way; salmon ladders have been made but
they don’t work very well. Another problem is the fish
get trapped in the machinery and there has been a
huge impact on the salmon population because of
this.
7. Construction
Dams can take up to 17 years to build and some of
them are so expensive that they need to operate for
decades to become profitable; the Hoover Dam cost
$690 million and the Three Gorges Dam in China cost
$37 billion.
8. Solutions
They could get electricity form other sources such as solar
or wind power.
They could build tubes deep underwater so fish and
sediment can get past.
They could build walls around the reservoir to prevent
flooding.
They could build lots of small dams instead of big ones to
prevent them from being too heavy and putting too much
pressure on the ground.
