Sorry for the delay in this post as I’ve recently been away
in the middle of nowhere for things related to my degree, but I’m back now.
I mentioned about dams in a previous post concerning river
health but I did not go into any kind of detail on them, as I believe it to be
suck a big topic that it requires a post all of its own. Dams are an extremely
controversial topic as they can be seen as both good and bad in different
people’s eyes.
There are a number of different reasons dams are built in
some cases it’s due to the requirement of water storage for large population,
to help drain areas of marshes so as to provide more land for agriculture and development
on or to provide a power source which is not dependent on fossil fuel or
nuclear power. Now it is the reason for the dam in my eyes which either make it
a good investment or not, and also the area which it is going to be built.
It is always important to remember that a dam does not just
effect the immediate environment behind it which becomes flooded upon
completion of the dams. Dams have repercussions which stretch for hundreds of
miles or even for the entire river.
Dams change ecosystems in a number of different ways; the
first thing I’m going to bring up is how they disrupt the movement of sediment
down the river. This works in two different ways, firstly sediment is held up
above the dams and as the water slows the sediment which is held in suspension,
settles out of the water and build up. Although this may appear good it’s not
all amazing as these sediment can built up and bury aquatic plants and other
forms of life and as the water builds behind the dam the bottom of the
resulting lake can become baron and lifeless. In fact a study conducted by the
World Bank in 1987 estimated that around 1,100 cubic kilometers of sediment was
accumulated behind the world’s reservoirs. That amount of 
Now onto a positive though, as if you block a river you
capture a lot of potential energy as the water is stopped. This water can then
be released and feed through turbines and produce clean electricity, the Three
Gorges Dam in central China is the world’s largest power producing facility of
any kind. Personally I’m all for alternative energy sources and believe that
our dependence on fossil fuels needs to be reduced as fast as possible. For instance in the UK 21% of its total energy
used is produced through renewable energy sources and of that 21% hydroelectric
power makes up 21%. That’s the third highest renewable energy source closely
following biomass then wind power. This is nothing however compared to places
such as Mozambique and Nepal both of which produced over 99% of their energy
needs through hydroelectric power in 2012.
A third use of dams or a secondary use of hydroelectric
power dams if for water storage, this is of course necessary due to the
increasing population numbers and the ‘wasteful’ sort of culture we live in.
For instance people within the UK use on average 150 liters of water a day personally;
this is a number which has been growing by 1% every year since 1930. Also when
the amount of water used to produce food and other products used by an
individual each day is factored in you will actually be consuming 3400 liters a
day. This is of course a major issue and
so dams are created to feed large populations with water when required. However
still in some cases these dams still are not enough to fulfill the demand, this
situation has been addressed by things such as reducing the amount of water
lost through evaporation. California for instance as filled a number of their
reservoirs with thousands of black plastic balls like those found in ball pits
so as to shield the water from the heat of the sun to reduce evaporation.
These reservoirs also produce a build-up of sediment like
any dam, but along with that they also reduce the amount of water flowing down
stream. Although not all the water is
held up and dams are constantly producing a compensation flow, there is still
drastically less water going downstream the majority of the time. This affects
general health of the ecosystem below reducing both the biodiversity and
carrying capacity of river, it will also affect the seasonal residents of the
river, for instance migratory fish such as salmon first of all struggle to
reach the dam and then being unable to reach their spawning sites. Furthermore
the large amount of still water provide efficient breeding grounds for disease
vectors, more of which can be read about in the link below which focuses on
Malaria.
Finally there are the economical effects of dams. Now
hydroelectric dams clearly have a form of economic income through the
production of electricity but the creations of dams change a rivers physiology
completely. This can result in the loss of river features such as rapids, and
meadows and fertile land above the dam which becomes flooded. Uganda has and is
still currently building dams across sections of the White Nile which contains
several sections of world class white water which attract thrill seekers from
across the world to raft and kayak. However the creations of the first and now
the second dam have flattened out large sections of the White Nile and reduced
income from tourism in that form.
It’s always a gamble whether the socioeconomic effects of a
dam are worth building it and it is not a standard answer. Ever individual case
is different and based on a series of variables such as effects to the
environment surroundings, human benefit vs human loss and potential of the dam
if built.
So if there is a dam being created close to you or anywhere
else in the world you cannot simply make a blanket decision, research and
knowledge is needed to create sensible opinion.
I’ve only skated over the pros and cons of dams and extra
reading can never hurt, if you have any good sources for or against dams please
comment.
(As a side note – It is also important to remember the
creation of a dam is extremely costly to the environment. For instance huge
machinery is used to divert water courses, and the millions of tonnes used to
produce the dam produce vast amounts of CO2)
Thanks for reading!
Just a few links
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