yes dam is called as multipurpose project because of following advantages :-
  - it helps to generate electricity , and for the purpose of irrigation 
  -  it is suitable for pisciculture and performs great role that leads to conservation of soil from huge distruction created by floods .
  - it also attracts as a tourist place due to the development of natural scenery .
  - it leads and promotes the water recreation and commands the navigation .

disadvantages :-
  - it became the cause earth quake 
  - it became the cause of water born disease 
  - it creates inter state dispute 
  - it poses the challenge of migration 
  - it also effects the ecosystem 
  - also cause deforestation and flood ( if dam get damaged or busted ) .