What is the difference between weir and barrage?

IF WATER FLOWS OVER AN OBSTRUCTION,IT IS CALLED A WEIR WHEREAS IF WATER FLOWS THROUGH AN OPENING WITH MECHANICALLY OPERATED GATES,IT IS CALLED BARRAGE

WEIR: It is an impervious barrier which is constructed across a river to raise the water level on the upstream side is known as a weir. Here, the water level is raised up to the required height and the surplus water is allowed to flow over the weir. Generally it is constructed across an inundation river.

BARRAGE: When adjustable gates are installed over a weir to maintain the water surface at different levels at different times is known as a barrage. The water level is adjusted by operating the gates or shutters. The gates are placed at different tiers and these are operated by cables from the cabin. The gates are supported on piers at both ends. The distance between the pier to pier is known as Bay.