Geological Conditions Necessary For Construction Of Dams

GEOLOGICAL CONDITIONS NECESSRY FOR CONSTRUCTION OF DAMS

DEFINITION

Ø     A DAM may be defined as a solid barrier constructed at a suitable location across a river valley with a view of impounding water flowing through that river. (1) generation of hydropower energy;

SELECTION OF SITES

Topographically

Ø     It would be a narrow gorge or a small valley with enough catchments area available behind so that when a dam is placed there it would easily store a calculated volume of water in the reservoir created upstream.

This should be possible without involving significant uprooting of population, loss of cultivable land due to submergence or loss of existing construction.

Technically

Ø     The site should be as sound as possible: strong, impermeable and stable.

Ø     Strong rocks at the site make the job of the designer much easy: he can evolve best deigns.

Ø     Impermeable sites ensure better storage inventories.

Ø     Stability with reference to seismic shocks and slope failures around the dam, especially upstream, are a great relief to the public in general and the engineer in particular.

Ø     The slips, slides, and slope failures around and under the dam and susceptibility to shocks during an earthquake could prove highly hazardous.

Constructionally

Ø     The site should not be far off from deposits of materials which would be required for its construction.

All types of major dams require millions of cubic meters of natural materials - earth, sand, gravel and rock -for their construction.

Economically

Ø     The benefits arising out of a dam placed at a particular site should be realistic and justified in terms of land irrigated or power generated or floods averted or water stored.

Ø     Dams are invariably costly structures and cannot be placed anywhere and everywhere without proper analysis of cost-benefit aspects.

Environmentally

Ø     The site where a dam is proposed to be placed and a reservoir created, should not involve ecological disorder, especially in the life cycles of animals and vegetation and man.

Ø     The fish culture in the stream is the first sector to suffer a major shock due to construction of a dam. Its destruction may cause indirect effects on the population.

Ø     These effects require as thorough analysis as for other objects. The dam and the associated reservoir should become an acceptable element of the ecological set up

of the area.