why it is necessary to know how much land will be submerged by water of the dam when it is planned
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Explanation:
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Submergence of Land
Submergence of lands behind a reservoir cannot be avoided. Usually, the dam site is selected to keep the submergence as small as possible, subject to the project objectives, and technical requirements of the dam foundation, abutment, and the reservoir. Usually, submergence is less than 10% of the benefited area. Although no hard and fast rule can be laid down, such submergence should not be more than 20% of the extent of the benefited area, because with larger submergence, problems of resettlement and rehabilitation become intractable. It may be noted that generally the displaced population is about 2-4% of the population benefited by the project. This issue is discussed in detail later in Section 7.10.
While large dams lead to submergence of the land area, they are not a major cause of deforestation. For example, even if all the envisaged dams in the Ganga basin are constructed, the submerged area of the forest will be less than 2%. Poor people in many countries depend on wood for domestic fuel requirements. The availability of cheap electrical energy by hydroelectric projects will help in reduction of deforestation because some fuel requirements can be met by electricity. In fact, a large number of trees are cut every year to meet the needs of packaging industries, timber for building construction, furniture and transport sector, etc. Indiscriminate grazing is also harmful to the forests.
As most dams are constructed in upper reaches of a river, submergence of forests and wasteland cannot be avoided. Clearly, there is a trade-off between submergence of cultivable and forest lands, or submergence of lands at one site against another site. However, the forest cover lost on account of WRD projects is a very small part of the total forest loss in a country. In any case, to reduce this loss, the permission to cut forest is usually given with the stipulation of compensatory afforestation. Various countries have evolved different norms. In India, for example, an area equivalent to five times the area of forest likely to be affected (submerged or cut for any of the project features, such as canal) is to be afforested and maintained for five years at project costs. The project estimates should provide about 1% of the project costs for this purpose. These provisions, if properly followed, should more than compensate for the ensuing de-forestation.
The reservoir may also submerge private agricultural or non-agricultural lands; such lands are required to be acquired under the prevailing land acquisition act. Experience shows that the land acquisition usually takes time and it is not feasible to strictly apply the legal provisions to such acquisition. Many matters are better sorted through dialogue and persuasion rather by confrontation.
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