What Is The Impact Of Construction Of Dams?

What Is The Impact Of Construction Of Dams
Environmental Impacts of Dams Low flows below dams killed thousands of salmon on the Klamath in 2002 The environmental consequences of large dams are numerous and varied, and includes direct impacts to the biological, chemical and physical properties of rivers and riparian (or “stream-side”) environments.

  1. The dam wall itself blocks fish migrations, which in some cases and with some species completely separate spawning habitats from rearing habitats.
  2. The dam also traps sediments, which are critical for maintaining physical processes and habitats downstream of the dam (include the maintenance of productive deltas, barrier islands, fertile floodplains and coastal wetlands).

Another significant and obvious impact is the transformation upstream of the dam from a free-flowing river ecosystem to an artificial slack-water reservoir habitat. Changes in temperature, chemical composition, dissolved oxygen levels and the physical properties of a reservoir are often not suitable to the aquatic plants and animals that evolved with a given river system.

  1. Indeed, reservoirs often host non-native and invasive species (e.g.
  2. Snails, algae, predatory fish) that further undermine the river’s natural communities of plants and animals.
  3. The alteration of a river’s flow and sediment transport downstream of a dam often causes the greatest sustained environmental impacts.

Life in and around a river evolves and is conditioned on the timing and quantities of river flow. Disrupted and altered water flows can be as severe as completely de-watering river reaches and the life they contain. Yet even subtle changes in the quantity and timing of water flows impact aquatic and riparian life, which can unravel the ecological web of a river system.

  1. A dam also holds back that would naturally replenish downstream ecosystems.
  2. When a river is deprived of its sediment load, it seeks to recapture it by eroding the downstream river bed and banks (which can undermine bridges and other riverbank structures, as well as riverside woodlands).
  3. Riverbeds downstream of dams are typically eroded by several meters within the decade of first closing a dam; the damage can extend for tens or even hundreds of kilometers below a dam.

Riverbed deepening (or “incising”) will also lower groundwater tables along a river, lowering the water table accessible to plant roots (and to human communities drawing water from wells), Altering the riverbed also reduces habitat for fish that spawn in river bottoms, and for invertebrates.

  1. In aggregate, dammed rivers have also impacted processes in the broader biosphere.
  2. Most reservoirs, especially those in the tropics, are significant contributors to greenhouse gas emissions (a recent study pegged global greenhouse gas emissions from reservoirs on par with that of the aviation industry, about 4% of human-caused GHG emissions).

Recent studies on the Congo River have demonstrated that the sediment and nutrient flow from the Congo drives biological processes far into the Atlantic Ocean, including serving as a carbon sink for atmospheric greenhouse gases. Large dams have led to the of many fish and other aquatic species, the disappearance of birds in floodplains, huge losses of forest, wetland and farmland, erosion of coastal deltas, and many other unmitigable impacts.


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What are the negative impacts of dams?

By Samantha Stahl The United States has 9,265 dams, second only to China which has a staggering 23,842. With climate change causing water shortages and storm surges, this might seem like good news. Dams store water, provide renewable energy and prevent floods.

What are the disadvantages of dam construction?

The building of large dams can cause serious changes to the earth’s surface and lead to geological damage. It can trigger frequent earthquakes, however, modern planning and design of dams have reduced the possibility of occurrence of certain disasters.

Why is dam construction a problem?

Dams are problem creators, not problem solvers What will 3,700 more new dams do that 48,000 existing ones haven’t already done? Invite more problems. According to a, the 3,700 new dams under construction or planned for construction around the world will not meet the electricity demands of the developing countries where the dams are planned.

Instead, these dams will pave the way for new ecological problems, reduce the number of free-flowing rivers around the world by 21%, and perhaps even cause conflict between countries over water. As explained, the dams will bring more problems than they will solve. Hydropower dams flood large areas, force people to relocate, threaten freshwater biodiversity, disrupt subsistence fisheries, and leave rivers dry – substantially affecting the ecosystem.

These dams will undoubtedly damage river systems, and even though they are being pushed as a source of renewable energy, it has been estimated that the methane emissions from hydropower reservoirs may be substantially higher than energy gains – perhaps contributing more than 20% of all man-made emissions.

Instead of solving the climate crisis, the dams will likely contribute to it. Here in the United States, we built many of our hydropower dams in the early- to mid-20th century when we did not have as good an understanding of our rivers and ecology as we do now. We also didn’t have environmental laws such as the Clean Water Act, Endangered Species Act, or the National Environmental Policy Act at the time to protect natural resources.

So, by building dams in a “primitive” era, we severely damaged many of our ecosystems. Examples include decline in salmon fisheries in the Columbia River basin and extinction of snails and mussel species in the Coosa River basin. By building dams, we choked the life out of rivers, thereby causing much damage to people, local economies, and the species that needed healthy rivers to survive.

We are now undoing the damage we caused by starting to remove dams. However, the developing countries that are planning to build dams don’t have to repeat the mistakes we made. As dams are being removed across the US and Europe the developing countries where these dams are planned should take a step back and consider the negative impacts dams have on their environment, people, and the economy.

While the intentions of dam-builders to generate new sources of energy may have been good, they are often short-sighted. Instead of building massive dams that will not solve any problems but instead invite newer problems, developing countries should be looking to invest in true renewables like wind and solar.

What are the positive and negative impacts of dams?

Dams have a great deal of positive and negative effects on the environment. Their benefits like controlling stream regime, consequently preventing floods, obtaining domestic and irrigation water from stored water and generating energy from hydro power.

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What are some positive and negative impacts of building dams?

Damming attitudes – Measured across the continent, Australia receives an average of only 465 mm of rainfall a year, compared with Europe’s 640 mm and Asia’s 600 mm. High evaporation allows just 12 per cent of our rainfall to run off and reach waterways.

  • Even so, there’s enough water for everyone – but it’s seldom in the right place at the right time.
  • European settlers solved this problem with dams.
  • The first two – Yan Yean outside Melbourne and Lake Parramatta, Sydney – were completed in 1857.
  • Dam building continued steadily until after WW II, when it accelerated.

Today, 500 large (more than 15 m high) dams store a total of 93,957 gigalitres. (Sydney Harbour holds about 562 GL.) There are also countless smaller dams, called weirs, on most Australian rivers – 8000 in the Murray-Darling Basin alone – and more than 2 million farm dams.

  1. Large dams bring quick benefits.
  2. They can provide water and electricity, mitigate flooding and create beautiful lakes.
  3. But they also have adverse impacts.
  4. The first are those on people living in the way of a dam and its lake.
  5. They may need to be moved, causing families and communities to fragment.
  6. The lake may flood farmland or natural landscape.

Many of the drowned river’s plants and animals fail to adapt to lake conditions. Alien fish species, introduced into the reservoir accidentally or for recreational fishing, may further alter the biological make-up of water life; and weeds and algae may thrive in the nutrient-rich water.

  • Downstream, changes in the river’s flow and water quality usually cause irreversible effects, often down to the river mouth and beyond.
  • Fish migration and reproduction, siltation and salinity in deltas are altered.
  • Once upon a time, these adverse impacts – some of which take years to manifest – weren’t really considered before a dam was built.

The human need for water, for drinking or to grow food, took precedence. Some people believe it should still. But over recent decades, science has deepened our understanding of natural systems, which we now know can’t be broken into discrete pieces, some of which can be exploited and others not.

This has given rise to the idea that the environment itself is a legitimate water consumer, with attendant needs and rights. All this calls for careful study of a river’s state and function before it’s dammed. “We need to consider rivers as ecosystems that provide goods and ecological services to society,” says Professor Angela Arthington, of the Australian Rivers Institute at Brisbane’s Griffith University.

“That argument is becoming very powerful globally and is forming the basis of a lot of the negotiations about how you manage rivers and where you place dams – if you do place them.” Impressive though it may be, Paradise, like other large dams, is a mix of good points and bad.

For some people, the bad prevail. High among the complaints has been that the rationale behind it was political. In the 1990s, the idea of a dam on the Burnett River was dismissed as uneconomic, but former Queensland Premier Peter Beattie made it an election promise in 2000. Then there are the potential environmental impacts downstream, especially around the river’s mouth in Hervey Bay, which worry people such as commercial fishers and tourism operators.

But nothing has galvanised public opinion more than the plight of the endangered Australian, or Queensland, lungfish. Among the last of a group that lived 400 million years ago, this once-abundant fish is restricted mostly to the Burnett and Mary rivers.

  1. Biologists believe Paradise Dam has had, and will have, serious consequences for it.
  2. The fishway was installed to comply with the Commonwealth’s Environmental Protection and Biodiversity Conservation Act (EPBC Act), which lists the lungfish as endangered.
  3. The Act requires the fish’s spawning and nursery habitat to be preserved.
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Jean Joss, Professor of Biology at Sydney’s Macquarie University, says lungfish spawn in slow-flowing shallows with plenty of native water plants. “When it is full, it will have permanently destroyed 42 km of lungfish spawning/nursery grounds,” she says.

Is construction of dams beneficial or harmful?

BENIFITS OF DAMS – Main Content Dams provide a range of economic, environmental, and social benefits, including recreation, flood control, water supply, hydroelectric power, waste management, river navigation, and wildlife habitat.

    Recreation Dams provide prime recreational facilities throughout the United States. Boating, skiing, camping, picnic areas, and boat launch facilities are all supported by dams. Flood Control In addition to helping farmers, dams help prevent the loss of life and property caused by flooding. Flood control dams impound floodwaters and then either release them under control to the river below the dam or store or divert the water for other uses. For centuries, people have built dams to help control devastating floods. Water Storage Dams create reservoirs throughout the United States that supply water for many uses, including industrial, municipal, and agricultural. Irrigation Ten percent of American cropland is irrigated using water stored behind dams. Thousands of jobs are tied to producing crops grown with irrigated water. Mine Tailings There are more than 1,300 mine tailings impoundments in the United States that allow the mining and processing of coal and other vital minerals while protecting the environment. Electrical Generation The United States is one of the largest producers of hydropower in the world, second only to Canada. Dams produce over 103,800 megawatts of renewable electricity and meet 8 to 12 percent of the Nation’s power needs. Hydropower is considered clean because it does not contribute to global warming, air pollution, acid rain, or ozone depletion. Debris Control In some instances, dams provide enhanced environmental protection, such as the retention of hazardous materials and detrimental sedimentation.

    What are the positive and negative impacts of dam?

    Dams have a great deal of positive and negative effects on the environment. Their benefits like controlling stream regime, consequently preventing floods, obtaining domestic and irrigation water from stored water and generating energy from hydro power.

    What are the positives and negatives of dams?

    Advantages and Disadvantages of Dams

    Advantages of Dams Disadvantages of Dams
    The reservoir built behind the dam can be used for water sports, irrigation, or even other types of pleasurable activities. The construction of huge dams leads to a major deterioration of the earth’s surface which causes geological harm.