Which of the following is not a disadvantage of building large dams?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Development of irrigational facilities
Assured irrigation is the chief benefit for which large dams are built, along with power generation, flood moderation and water supply — so it is not a disadvantage.
The genuine costs are the others: reservoirs fragment river and forest habitats and block fish migration, canal irrigation without drainage causes waterlogging and salinisation, and organic matter rotting under the reservoir releases methane and carbon dioxide.