Pakistan or any other country even needs dams to fulfill its energy requirements in a very effective and simple manner. The basic benefit is that the water used is collected from a very natural resource i.e.rain and can be used and reused to produce energy and electricity. If efficient measures are taken, deterioration of dams can also be prevented. Also in hours of need, the water stored can be used in irrigating the lands (agriculture being the backbone of Pakistan's economy). It will solve the problem by producing the electricity we lack, by helping the irrigation of lands when we don't have water and what not. Although other methods of energy production also exist, for a developing country like Pakistan, its better to go for an easier and relatively cheaper method.
