Question

what is the use of reservoir

Answer 1

A reservoir is an artificial lake where water is stored. Most reservoirs are formed by constructing dams across rivers. A reservoir can also be formed from a natural lake whose outlet has been dammed to control the water level. The dam controls the amount of water that flows out of the reservoir.

Answer 2

During droughts, the water level in a river may be very low. Under these conditions, more water is released from the reservoir so farmers can water their crops and homes and businesses can function normally.
Reservoirs serve other purposes like boating, fishing, and other forms of recreation. Some of the dams that create reservoirs are used to generate electricity.

hope it helps!!