Question

why environmental aspects must be carefully looked into before building huge dam

Answer 1

Dams are really very Harmful for Environment. Dams prevent Natural flow of rivers. Building dams submerge a huge amount of land resulting in destruction of vegetation of that area. Forests and wildlife gets destroyed. Over time. Fish and prawn populations will be heavily affected many may even become extinct because migrations to breeding grounds are disrupted in the rivers above and below the dam.