Answer:
Dams are constructed over the narrow valleys and it acts like a barrier that obstructs the water from the flow. There are both advantages as well as disadvantages in constructing a dam.
Some of the constructive force or advantages of dams are as follows-
1) It generates electricity
.
2) It is often used for irrigation and industrial purposes.
3) it is used for farming purposes in water such as raising as well as harvesting of fishes and other aquatic plants.
Some disadvantages are-
1) It degrades water quality.
2) Aquatic organisms are affected thereby harming the ecosystem.
3) It obstructs the flow of water.
4) Failure of a dam causes flood.
