Before any decision is taken to build a
dam for whatever purposes ~ public water supply, energy, irrigation,
flood control ~ the first question that should be asked is: “Is the
It should not be implicitly assumed that it
will be meeting a real need. It may be that demand side management could
reduce the need or that the demand has been overestimated.
For an investment as large as a dam, an
accurate needs assessment is essential – otherwise the project may
fail to satisfy its objectives and produce a suitable return.
These considerations are not purely
academic. If a real demand has been established then any dam which is
subsequently built is also likely to be a better investment.
On the other hand if a dam is built to
satisfy unsubstantiated demand projections, it will be less secure as an
Dam construction can
have environmental benefits, although some of these may not be planned
However, dams have
caused much more environmental damage than they have brought benefits.
Biodiversity loss is caused by dam
construction. Habitats are lost, both in the reservoir area and
downstream. This is what is likely to happen should the
Talo Dam In Djenne ( Mali ) go ahead. Some dam projects,
like the Kárahnjúkar
project in Iceland, threaten some of our last wilderness areas.
There is concern about the high levels
of emissions of greenhouse gases such as carbon dioxide and methane,
from some dams in the tropics with shallow reservoirs. In the
initial stages, the emissions are mainly due to the rotting of
flooded vegetation, but this process usually continues with the
deposition of organic matter by in-flowing streams. More research
into this matter is needed urgently.
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