Dams And Resources Essay

While the free essays can give you inspiration for writing, they cannot be used 'as is' because they will not meet your assignment's requirements. If you are in a time crunch, then you need a custom written term paper on your subject (dams and resources)
Here you can hire an independent writer/researcher to custom write you an authentic essay to your specifications that will pass any plagiarism test (e.g. Turnitin). Waste no more time!

The Environmental Impacts of Large Dams

Land and water are ecologically linked in a natural system called a watershed. From the smallest

droplet to the mightiest river, water works to shape the land, taking with it sediment and dissolved materials

that drain to watercourses and, in most cases, eventually to the sea. So is the river a product of the land it

inhabits--the type of rock and soil, the shape of the land, and the amount of vegetation are some of the

factors that determine the river's shape, size and flow.

When these ties between the land and the river are broken by a large dam, the consequences are felt

throughout the watershed, as well as by the web of life it supports. Of all the ways to tamper with or harm a

river, a large dam usually has the most immediate and far-reaching effects because of the huge changes it

causes to river circulation system.

Some 40,000 large dams, most of which were built in the past 50 years, now obstruct the world's

rivers. More than 400,000 square kilometers--an area larger than Zimbabwe, and 13 times the size of

Lesotho. Volta Reservoir behind Ghana's Akasombo Dam, flooded 4% of that nation's land area. In the

United States, whose 5,500 large dams make it the second most dammed country in the world, we have

stopped building large dams, and are now spending great amounts of money trying to fix the problems

created by existing dams.

Although the impacts of large dams have been well documented for some time now, in case after

case, new ones are proposed whose environmental impacts are downplayed or even ignored. A suvey

showed that most dams were built without the consideration of downstream effects, even when these

impacts could be predicted to cause massive coastal erosion, pollution, and other problems.

Reducing the flow of water from a river changes the landscape it flows through, which in turn can

affect the ecosystem's flora and fauna. A dam holds back sediments, especially the heavy gravel and cobbles.

The river, deprived of its sediment load, seeks to recapture it by eroding the downstream channel and banks,

and other riverbank structures. Riverbeds are typically eroded by several meters within a decade of first

closing a dam; the damage can extend for tens or even hundreds of kilometers below a dam. Within nine

years of closing Hoover Dam in the US, the riverbed below the dam had lowered by more than 4 meters.

Riverbed deepening will also lower the groundwater table along a river, threatening vegetation and local

wells in the floodplain and requiring crop irrigation in places where there was previously no need. The

reduction of riverbed gravels reduces habitat for many fish that spawn in the gravelly river bottom, and for

invertebrates such as insects, molluscs, and crustaceans.

Before the Aswan High Dam, the Nile River carried about 124 million tons of sediment to the sea

each year, depositing nearly 10 million tons on the floodplain and delta. Today, 98% of that sediment

remains behind the dam. The result has been a drop in soil productivity and depth, among other serious

changes to Egypt's floodplain agriculture. The Aswan Dam has also led to serious coastal erosion, another

problem stemming from the loss of sediments in a dammed river. Another example of this problem is along

the mouth of the Volta River in Ghana. This dam has cut off the supply of sediment to the surrounding

rivers, whose coasts are now being eaten away at a rate of 10-15 meters per year. A project to...

You should cite this paper as follows:

MLA Style
. EssayMania.com. Retrieved on 23 May, 2012 from
    <http://essaymania.com/133404/dams-and-resources>

More College Papers

Daltons Atomic Theory essay
John Dalton developed the first useful atomic theory of matter around 1803. In the course of his studies on meteorology, Dalton concluded that evaporated water exists in air as an independent gas. Solid bodies can't occupy the same space at the same time, but water and air could. If the water and ai

Cystic Fibrosis 2 essay
Cystic Fibrosis Cystic Fibrosis is an inherited disease that is present at birth and is characterized by chronic lung infections and the inability to absorb fats and other nutrients from food. When Cystic Fibrosis was first identified in the 1930's, it claimed the lives of almost all of its victoms

Bacterial Resistance essay
Bacterial Resistance Bacterial resistance is a problem that has profoundly impacted the medical community. Bacterial resistance results when bacteria become resistant to individual antibiotics through the development of specific defense mechanisms which render the antibiotic ineffective. This pro