1) social problems as they displace a large number of farmers and tribals
2 ) economic problems as they consume a huge amount of public money without proportionate benefit
3)environmental problem as they cause deforestation and loss of biological diversity

2 3 2
There r several problems..
some r as follows:
1. they require a large amount of money for constructions.
2. farmers r not able to do farming as their grazing land got snatched by govt.
3. environmental problems may led to deforestation