Question

Describe the environmental impact of construction of big dams.

Answer 1

here is your answer OK dude

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Dams flood the catchment areas removing habitat and degrade the river downstream of the dam. Estuaries can become can become stagnant by being blocked or insufficient water flow. The progress of fish like salmon is blocked. Silt deposits at the dams instead of over the flood plains and salt also accumulates. It is believed that some great civilizations were built around dams only to die out “overnight” because the salt level in the dam reached critical levels.

There is a great deal of actual observable change in nature that has been going on. No engineer who is responsible can predict where it is heading. The 'wait and see' policy does nothing to mitigate or change: but for an engineer that would be the irresponsible course of action.