Why are large dams opposed by environment?
Answers
A large dam is defined by the dam industry as one higher than 15 metres (taller than a four-story building). There are more than 57,000 large dams worldwide. There are more than 300 major dams - giants which meet one of a number of criteria on height (at least 150 metres), dam volume and reservoir volume.
China has over 23,000 large dams. The US is the second most dammed country with some 9,200 large dLarge dams have provoked opposition for numerous social, environmental, economic and safety reasons. The main reason for opposition worldwide are the huge numbers of people evicted from their lands and homes to make way for reservoirs. The livelihoods of many millions of people also suffer because of the downstream effects of dams: the loss of fisheries, contaminated water, decreased amounts of water, and a reduction in the fertility of farmlands and forests due to the loss of natural fertilizers and irrigation in seasonal floods. Dams also spread waterborne diseases such as malaria, leishmaniasis and schistosomiasis. Opponents also believe that the benefits of dams have frequently been deliberately exaggerated and that the services they provide could provided by other more efficient and sustainable means.ams, followed by India, Japan, and Brazil.The rate at which large dams are completed has declined from around 1,000 a year from the 1950s to the mid-1970s to around 260 a year during the early 1990s. More than 3,700 hydropower projects are planned or under construction on the world’s rivers as of 2014. If built, they could block free-flowing rivers by more than 20%.
large dams are opposed because
- they have high initial cost
- they are labour intensive
- they take large time build
- they can cause problems they are supposed to prevent like earthquakes and floods
- they caused degradation
- they displace lot of people
- they destroy natural habitat
- they caused sedimentation
- they do not allow aquatic life to spawn and breed