give to argument in favour of small dams over large dams
Answers
The Agricultural Division of World Bank listed a number of arguments in support of large dams. The arguments summarise the views of a number of development planners and engineers in support of large dams. An excerpt of their defence is presented below. The context was their defence on the Sardar Sarovar Dam.
While small dams have a role and are, indeed, a significant part of the overall development proposals for the Narmada Basin, they do not, and cannot approach the scale of the benefits of the larger dams. First they are not as low cost as is often claimed: a study of small “tanks” (as they are called) in India by an International Research Institution found most of them to be uneconomic (partly because of the amount of the land they inundate relative to the water stored).
Second, while a few good small dam remains that could be developed at modest cost, the cost escalates greatly as in the search for the large numbers of small dams needed for storing significant volumes of water, one is compelled to tackle increasingly less suitable sites.
Third, they fail to fill in the very year, the dry year, when they are needed the most. It was only the large dams that performed adequately for Gujarat in the last drought. Fourth, they inundate relatively massive areas of land; in the lower parts of basins this tends to be very fertile agricultural land, in the upper parts forest.
Typically small “tanks” of around 40 to 100 ha. size inundate almost as much land as they irrigate, around 0.9 of a hectare for every 1.0 hectare (usually irrigating one crop only, whereas large dams irrigate much more than one, apart from also providing power). Sardar Sarovar will inundate only about 1.6% of the area irrigated. Thus even if it were technically possible to find enough small dam sites to store the same amount of water, the land lost to inundation could well be over 1 million hectares as opposed to about 37,000 ha. for the Sardar Sarovar Reservoir.
An important issue raised by the defenders of large dams is the over-exploitation of ground water for irrigation purposes. The small dams have according to them proved to be poor substitutes, as people still continue to rely on ground water for their most essential and regular requirements. With regards to the detrimental consequences of large dams, the proponents of large dams admit that large dams do submerge large tracts of forests, but also draw attention to the fact that the loss of forest in the Narmada Basin has been at the rate of about 20,000 ha per annum without the large dam in place or any other mega development project.
This is a significant observation not only about the state of forest management in the country as a whole, wherein forest products are being extracted indiscriminately by encroachers and commercial interests, but also the increasing pressure on forests to fulfill subsistence needs of the people. This brings out the levels of corruption, malpractice and inefficiency that exist in India, with or without large dams. Development initiatives thereby get a bad name, as the discrepancy in the implementation process is passed on to the plan itself.