How about this as it pertains what is in the new seir report.....
The Environmental Impacts of Hydroelectric Power
by
Eric Boissonneault
Last updated: 12/05/2001 08:25:50
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Hydroelectric power does not produce the thick black smoke of a coal fired power plant, or the harmful waste of a nuclear power plant, but hydroelectric projects can be the source of other environmental problems. The harmful impacts of altering river systems to produce power can have harmful impacts on both human and aquatic communities in the area surrounding a hydroelectric project.
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Introduction:
Electricity playes an every increasing roll in the average persons life. Because it has become so important we have tried to find many ways in which to produce electricity in a cost-effective manner. In order to make the power "artificially" cheap the environmental impacts of producing electricity are often ignored. We now know that the environmental impacts of producing power have a real affect on the earth's systems, and that these affects can no longer be ignored. There are two things that now need to be done to minimize the impact of power production on our planet. First we need to lower our consumption of electricity, and second we need to produce cleaner power.
Often times when people speak about cleaner power they think of power production methods that do not cause air pollution or require the disposal of harmful waste, however pollution from power production can take many forms. Hydroelectric power is thought to be one of the cleaner ways in which to produce electricity, but it does have its' bad side. The environmental impacts of producing power using large hydroelectric dams is greater then the benefits that are gained from this power.
Abstract:
General Hydropower Information:
There are currently more then 2,300 hydroelectric dams in the US (Schueller, 2001).
Hydropower accounts for about 11% of the electricity supply in the US (Schueller, 2001).
Hydro plants can be owned by just about anyone including: federal, state, and local governments, utility companies (public and private), irrigation companies, and metropolitan water districts ( Brookshier and Sommers, 2000).
Of the 80,000 dams in the US, only 3% are used to produce electricity (FWEE, 2000).
As Figure 1 shows Canada and the US are the two largest producers of hydroelectric power in the world.
Figure 1: Who is Producing Hydropower (WVIC, 2000).
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Effects on Fish:
There are many ways in which a hydroelectric dam can affect the fish living in that particular river system. One of the more common concerns has to do with the blocking of spawning grounds for migrating fish. In the US this issue is often associated with the northwestern states, but it is also an issue for fish spacies alone the east coast. Salmon have long used the large rivers of the northwest as spawning grounds, it is estimated that 10 to 15 million salmon traditionally used the Columbia River as their spawning grounds (Reisner, 2000). Now on the Snake River (a tributary of the Columbia) four dams block the fish from reaching their spawning grounds. This has led to the listing of every species of salmon found on the Snake River as either extinct or endangered (FOE, 2000). Figure 2 shows the number of dams in the Columbia River system that the salmon must get past in order to reach their former spawning grounds.
Figure 2: Dams that fish must get past to reach spawning grounds (Flint, 2001).
Fish that do get by the dams and spawn are not guaranteed that their genes will live on. Of 1000 eggs that are fertilized, it is estimated that only 1 will survive to adulthood ( Reisner, 2000). This is due to many different factors. Salmon travel in fast cool waters, when they enter into the warmer, slower moving water behind a dam it takes them a long time to find their way past the dam and down the river. This extra time allows predator fish to feed on more of the young salmon. The warm waters behind a dam make for prime recreational fisheries for warm water fish, however these fish prey on the salmon and can have a major impact on the number of salmon smolts that make it past a particular dam. When you multiple this by the number of dams that one fish may have to travel past, it amounts to much better odds for the predator then the prey.Young fish can also be affected by the turbines that generate the power. These turbines generate high pressures that can crush young salmon smolts (Reisner, 2000).
As water travels over a dam it will hit the bottom pool with great force and cause an increase in the amount of air that is in the water. Since air is 78% nitrogen, the levels of dissolved nitrogen will greatly increase. When fish travel from an area that has high levels of nitrogen to areas of low nitrogen they can develop air bubbles in their bloodstream. These air bubbles can then lead to injury or death of the fish. (FWEE, 2000).
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Changes in the Movement of Sediments:
A dam will block the natural flow of sediments down a river system. This can have many different affects. For one it will block the passage of gravels used by fish for spawning. Blocking of gravels can also cause the river below a dam to erode its own bed and banks, which in turn can lead to lowering the groundwater table along a river, and the undermining of bridges and other structures along a river ( Pottinger, 2001). Dams will also stop or reduce the size of floods. While this may seem like a good aspect of dams, these floods provide the sediment nutrients that plant species along a river need for growth and reproduction. Since many of the most productive natural areas are along rivers the reduction in flood size and frequency will lead to a gradual decline in the productivity of these lands ( Pottinger, 2001). As the plant production is decreased so to will the health of animal communities that use these plants.
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Flooding Caused by Impoundments
Once an area is flooded the power company will often raise and lower the water levels depending on the need for power. When this happens the normal vegetation that would become established along the banks cannot become established. This can lead to increased erosion along the banks of the reservoir.
Flooding also may force the removal of native people. Not only are native people going to lose their lands, but also with the increased access to native lands from new roads these people will often loose much of their culture. These people are led to believe that the hydro projects will raise their standard of living by providing electricity and new jobs. However, degrading the environment which provides their traditional livelyhood, often outweighs any gains that they receive. Often these populations also show a decrease in health do to a reduction in the quality of their water. This aspect is addressed in the water quality section.
In many developing nations where large reservoirs have been created behind hydroelectric ther has been an increase in health problems. A large reservoir will attract mosquitoes, which in turn can spread diseases, such as malaria, through the human population much faster then normal (Freeman, 2000).
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Water Quality
Hydroelectric dams can have a major impact on the quality of the water that is held behind them. One of the major concerns with water quality has to do with the build up of toxic mercury in the water. Mercury is naturally leached from the earth by water, however when a dam blocks the flow of water this mercury can build up in the water to higher then normal levels (May, 1994). If the flooded area behind a dam is full of organic matter, bacteria can turn the insoluable mercury that is present into soluable methyl-mercury (Raphals, 1992). Methyl-mercury can then accumulate in the biomass of fish, and has been shown to be the cause of many human health problems. In the area flooded by the James Bay hydro project in Quebec Canada methyl-mercury levels have gone up dramatically. The native Cree that live in this area rely heavily on fish as a food source, and as is shown in Figure 3 the amount of mercury in the fish has increased since the project began.
Figure 3: Mercury present in the pike population (Dumont, 1995).
Another water quality issue has developed in other parts of the World. Many developing nations are being targeted for hydroelectric projects, however in many of these nations industrial and human waste is released directly into rivers. Damming these rivers will "turn the river into a cesspool of human and industrial wastes" (Freeman, 2000).
Water quality is also affected by the stratification of water behind a dam. This is when the warmer water on top traps colder water below it. This will lead to lower oxygen levels in the colder water. When this colder water is released to produce electricity it will have a negative impact on the aquatic ecosystem below the dam.
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Reference List
Brookshier,Peggy and Garold Sommers, 2000. Hydropower Program: US Department of Energy. Retrieved on 20 January, 2001 from the World Wide Web:
http://www.inel.gov/national/hydropower/more.htm.
Dumont, C., 1995. Proceedings of the 1995 Canadian mercury network workshop mercury and health: The James Bay Cree experience. Retrived on 13 February, 2001 from the World Wide Web:
http://www.cciw.ca/eman-temp/reports/publications/mercury95/part4.html.
Flint, Tom, 2001. The Dams. Retrived on 5 Febuary, 2001 from the World Wide Web:
http://www.saveourdams.com/snake_columbia_dams.htm.
The Foundation for Water and Energy Education, 2000. Hydro Tours. Retrieved on 20 January, 2001 from the World Wide Web:
http://www.fwee.org/Tours.html.
Freeman, Aaron, 2000. Financing Disaster.Canadian Dimension 34:18.
Friends of the Earth, 2000. Lower Snake River Campaign. Retrieved on 25 January 2001 from the World Wide Web:
http://www.foe.org/foenw/rivers/snake.html.
Higgens, Margot, 2000.Kennebec River revived after Edwards Dam removal. Retrived on 5 Febuary, 2001 from the World Wide Web:
http://www.enn.com/news/enn-stories/2000/06/06302000/edwards_14337.asp.
May, Elizabeth, 1994. Native garden of the north. Sierra79:130.
Pottinger, Lori, 2001. The Environmental Impacts of Large Dams. Retrived on 25 January, 2001 from the World Wide Web:
http://www.irn.org/basics/impacts.shtml
Raphals, Philip, 1992. The hidden cost of Canada's cheap power. New Scientist133:50-55.
Reisner, Marc, 2000. Unleash the Rivers: Dams are responsiblefor some of the worst environmental tragedies in history. We're starting at last to take some down.Time 155:66.
Schueller, Gretel H., 2001. Hydropower Threatens Nation's Rivers. Retrieved on 20 January, 2001 from the World Wide Web:
http://www.enn.com/news/enn-stories/2001/01/01102001/hydropower_41184.asp?P=1.
Wisconsin Valley Improvement Company, 2000. Facts About Hydropower Retrived on 31 January, 2001 from the World Wide Web:
www.wvic.com/hydro-facts.htm
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