Ecological impacts of Ecological impacts of dams and water diversionsdams and water diversions

http://www.virtualmuseum.ca/Exhibitions/Hydro/_img/dams/feature/libby.jpg

Definition and effects of damsDefinition and effects of dams

A dam is an artificial barrier put into flowing A dam is an artificial barrier put into flowing water in order to create a reservoir or a lakewater in order to create a reservoir or a lake

Every river has its unique flow, flora and fauna Every river has its unique flow, flora and fauna and environment around it (landscapes)and environment around it (landscapes)

Thus each dam is constructed with regard to the Thus each dam is constructed with regard to the specific riverspecific river

That is why all dams have different impacts on That is why all dams have different impacts on the riversthe rivers

Impact on fishImpact on fish Migratory fish (born in rivers, migrate to the sea or ocean to mature Migratory fish (born in rivers, migrate to the sea or ocean to mature

and go back to rivers to reproduce and in most cases die after that)and go back to rivers to reproduce and in most cases die after that) Some dams do not have the so called fish ladders (or other Some dams do not have the so called fish ladders (or other

constructions) which allow migratory fish, for example salmon, to constructions) which allow migratory fish, for example salmon, to reach the upstream of the river and the oceanreach the upstream of the river and the ocean

Grand Coulee Dam on the Columbia River in Washington has no Grand Coulee Dam on the Columbia River in Washington has no fish passage facilities and thus it kills salmon worth 250 000 $ a fish passage facilities and thus it kills salmon worth 250 000 $ a yearyear

But even if there are fish ladders in most cases only adult fish can But even if there are fish ladders in most cases only adult fish can pass through them, while their offspring finds it very difficult and it pass through them, while their offspring finds it very difficult and it costs them timecosts them time

The time is extremely important, because when the migration is The time is extremely important, because when the migration is delayed, the whole life cycle of the fish is behind schedule and fish delayed, the whole life cycle of the fish is behind schedule and fish can lose their ability to switch from fresh to salt water or to swim can lose their ability to switch from fresh to salt water or to swim downstreamdownstream

Example: It took salmon from the Snake River in Idaho less than 3 Example: It took salmon from the Snake River in Idaho less than 3 days to get to the sea before the dams were built compared to the days to get to the sea before the dams were built compared to the 39 days it needs now39 days it needs now

Impact on fishImpact on fish Many predator fish gather around dams and they are a potential Many predator fish gather around dams and they are a potential

threat to the smoltsthreat to the smolts Birds enjoy a rich feast, because the water around dams is not so Birds enjoy a rich feast, because the water around dams is not so

deepdeep In a reservoir, water on top is too warm, and at the bottom it is In a reservoir, water on top is too warm, and at the bottom it is

cooler and deeper, but with lack of oxygen cooler and deeper, but with lack of oxygen Water in reservoir contains high level of pollutants, lethal to any fish Water in reservoir contains high level of pollutants, lethal to any fish

or organismor organism Dams twirl water and fish, even these which are adapted to fast Dams twirl water and fish, even these which are adapted to fast

current may get pulled into the intakes of the dams and killedcurrent may get pulled into the intakes of the dams and killed Habitats of organisms get changed, e.g. new species invade slow Habitats of organisms get changed, e.g. new species invade slow

current areas thus increasing competition for resources and causing current areas thus increasing competition for resources and causing extinctionextinction

More than 95% of the smolts in Snake River may die before getting More than 95% of the smolts in Snake River may die before getting to the oceanto the ocean

http://www.nwcouncil.org/history/images/fishpassage.jpg

Impact on sediment flowImpact on sediment flow

Sediment is usually picked up along banks and stream Sediment is usually picked up along banks and stream beds, then carried downstreambeds, then carried downstream

Sediment provides nutrients for the fish and other Sediment provides nutrients for the fish and other organisms which live in riversorganisms which live in rivers

When a dam is built the sediment is collected behind it When a dam is built the sediment is collected behind it and the water bed below the dam becomes rocky and and the water bed below the dam becomes rocky and with no sedimentwith no sediment

Thus organisms have no food and aquatic plants can’t Thus organisms have no food and aquatic plants can’t tackle to the water bedtackle to the water bed

Thus, the lack of sediment leads to extinction of large Thus, the lack of sediment leads to extinction of large numbers of organismsnumbers of organisms

Impact on water qualityImpact on water quality Dams tend to collect pollutants and toxins with the sediment and water Dams tend to collect pollutants and toxins with the sediment and water

behind dams is extremely dangerous for any species downstreambehind dams is extremely dangerous for any species downstream Deeper dams do not allow the current to mix the water and the water near Deeper dams do not allow the current to mix the water and the water near

the surface is hotter than it should be, and the deeper water is vey cold, but the surface is hotter than it should be, and the deeper water is vey cold, but with almost no oxygen circulationwith almost no oxygen circulation

During the warm season, great amounts of water evaporate, because dams During the warm season, great amounts of water evaporate, because dams increase the water surface directly exposed to sun raysincrease the water surface directly exposed to sun rays

170 cubic kilometers water evaporates every year, which is more than 7% of 170 cubic kilometers water evaporates every year, which is more than 7% of the all used by humans freshwater (all activities)the all used by humans freshwater (all activities)

Example: 10% of the storing capacity of the High Aswan Dam in Africa Example: 10% of the storing capacity of the High Aswan Dam in Africa evaporates every year and these 11.2 cubic kilometers are roughly the same evaporates every year and these 11.2 cubic kilometers are roughly the same amount of water as that used for both residential and commercial use on the amount of water as that used for both residential and commercial use on the continentcontinent

The high level of evaporation (e.g. 1/3 of the Colorado River!!) leads to The high level of evaporation (e.g. 1/3 of the Colorado River!!) leads to increase in salinity which is poisonous to all aquatic organisms and causes increase in salinity which is poisonous to all aquatic organisms and causes great damages to the machinery and pipes (corrosion) great damages to the machinery and pipes (corrosion)

Example: Millions of dollars per year is the cost of the increased salinity in Example: Millions of dollars per year is the cost of the increased salinity in Colorado RiverColorado River

The Mahaweli mega scheme The Mahaweli mega scheme

A five-dam mega scheme in Sri LankaA five-dam mega scheme in Sri Lanka Has the purpose to irrigate previously forested areasHas the purpose to irrigate previously forested areas Due to its building the habitat of seven endangered and two Due to its building the habitat of seven endangered and two

threatened animals was turned into agricultural landthreatened animals was turned into agricultural land The two threatened species are the purple-faced langur and The two threatened species are the purple-faced langur and

the toque macaque (both monkeys) live only on the island Sri the toque macaque (both monkeys) live only on the island Sri LankaLanka

800 elephants live in this area and this specie is endangered. 800 elephants live in this area and this specie is endangered. They migrate and the reservoirs and canals are an obstacle in They migrate and the reservoirs and canals are an obstacle in on of their migratory routes. That is why they go through the on of their migratory routes. That is why they go through the farmland causing much trouble to the farmers and to other farmland causing much trouble to the farmers and to other animals in the area. animals in the area.

The Victoria Dam, part of the The Victoria Dam, part of the Mahaweli mega schemeMahaweli mega scheme

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Parana River, Itaipu ReservoirParana River, Itaipu Reservoir

http://www.leonardo-energy.org/files/root/EPQU/Images/unsorted/itaipu.jpg

Sete Quedas WaterfallSete Quedas Waterfall Dams not only affect life and environment, they also

destroy beautiful scenery At the Brazilian-Paraguayan border the Paraná River

suddenly narrows to only 60 meters width and then divides to 18 waterfalls (each more than 30 meters high)

A French traveler from the 19th century commented on this spectacular view: “A more imposing spectacle can scarcely be conceived.”

One of these waterfalls, Sete Quedas, was flooded by the Itaipú Reservoir, and is now only a rock formation below the reservoir

A great loss to Earth’s heritage

http://www.hotelfaguile.com.br/imagens/cataratas/images/1.jpg

http://www.pedromartinelli.com.br/blog/wp-content/uploads/2009/02/sete.jpg

Works CitedWorks Cited

"Impacts of Dams on Rivers." "Impacts of Dams on Rivers." FAO Corporate Document RepositoryFAO Corporate Document Repository. Food and . Food and      Agriculture Organization of the United Nations, n.d. Web. 5 June 2010.      Agriculture Organization of the United Nations, n.d. Web. 5 June 2010.      <http://www.fao.org/docrep/005/y3994e/y3994e0i.htm#TopOfPage>.      <http://www.fao.org/docrep/005/y3994e/y3994e0i.htm#TopOfPage>.

McCully, Patrick. "Dams and Migratory Fish." McCully, Patrick. "Dams and Migratory Fish." International RiversInternational Rivers. Creative . Creative      Commons, 1 Jan. 2001. Web. 5 June 2010.      Commons, 1 Jan. 2001. Web. 5 June 2010.      <http://www.internationalrivers.org/en/node/1639>.      <http://www.internationalrivers.org/en/node/1639>.

McCully, PatrickMcCully, Patrick. "Dams and Water Quality." . "Dams and Water Quality." International RiversInternational Rivers. Creative Commons, 1 Jan. . Creative Commons, 1 Jan.      2001. Web. 5 June 2010. <http://www.internationalrivers.org/en/node/      2001. Web. 5 June 2010. <http://www.internationalrivers.org/en/node/      1638>.      1638>.

McCully, Patrick. "Rivers No More: The Environmental Effects of Large Dams." McCully, Patrick. "Rivers No More: The Environmental Effects of Large Dams."           International RiversInternational Rivers. Creative Commons, 1 Jan. 2001. Web. 5 June 2010. . Creative Commons, 1 Jan. 2001. Web. 5 June 2010.      <http://www.internationalrivers.org/en/node/1636>.      <http://www.internationalrivers.org/en/node/1636>.

Smith, S. E. "Why are Dams Potentially Harmful to Fish?" Smith, S. E. "Why are Dams Potentially Harmful to Fish?" Wise GeekWise Geek. N.p., 12 . N.p., 12      Apr. 2010. Web. 5 June 2010. <http://www.wisegeek.com/      Apr. 2010. Web. 5 June 2010. <http://www.wisegeek.com/      why-are-dams-potentially-harmful-to-fish.htm>.      why-are-dams-potentially-harmful-to-fish.htm>.