Impact of Dams

Dams, and more specifically hydroelectric power, provide the modern day world with a large portion of our electricity.  So how do these dams generate such an immense amount of power?  A river is blocked off first, to allow the construction process to take place.  Than a large concrete barricade is erected, and fitted with turbines and a path for the water to contact them.  The difference in water level pushes water through channels in the dams.  This water rushes past turbines spinning them.  The turbine in the generator is connected to a shaft, which suspends large electromagnets.  The spinning of these magnets at high speeds generates a flow of electrons, also known as electricity.  Some countries like Canada and Australia, have an extremely significant amount of their power generated this way.  The largest dam in the world is the ThreeGorges Dam in China. 

Dams have little to no air pollutants generated.  In fact, dams generate almost no waste products at all.  So why are we not building dams on every waterway?  Well actually in the United States we are doing quiet the opposite.  We are actually taking down a lot of dams.  This is for an array of reasons, but the biggest being environmental impact, which at first glance seems very low.  But there are to many negative impacts to count in some ways.  The first being displacement.  Building a dam raises the water up stream, often creating lakes.  All to often, this makes thousands of people relocate, especially in countries like China, were the government seems all too willing to relocate citizens.  Disrupting the natural path of water seems to have a large impact on wildlife.  Fish that have a natural migration pater up these waterways like salmon, can no longer make this journey.  And because they are usually headed up stream to bread, this means a severe decrease in population.  Slowing water flow also makes water more stagnant upstream, which makes the dissolved oxygen content go down.  This also usually means fish found upstream from a dam have increased parasites, and are more susceptible to infection.  Down stream we see these effects for a different reason.  As the water goes through the dam it usually heats up.  This is either because it runs in a shallow stream down a shoot, or because the water is used to cool moving parts, in turn heating it up.  So downstream from the dam we see increased water temperature.  This encourages bacteria and algae growth, which means lower dissolved oxygen.  Also warmer water is not as capable of holding dissolved oxygen.  This really hurts the ecosystem, because the wildlife in rivers are usually very delicate.  So all this makes us ask ourselves are dams worth it.  On one side, fewer dams means more energy generated from fossil fuels, which harm the environment too.  But on the flip side, dams harm the environment in other ways, and require a lot of resources to build.  In conclusion, we need to access the impact for that specific area to really decide if it is worth it.