WEIR, BARRAGE AND DAM
An impervious barrier which is constructed across a river to raise the water level on the upstream side is known as 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.
When adjustable gates are installed over a weir to maintain the water surface at different levels at different times, then it is known as Barrage. The water level is adjusted by operating the adjustable gates or shutters. The gates are placed at different tiers and these are operated by cables from the cabin. The gates are supported on the piers at both ends. The distance between pier to pier is known as Bay.
The high impervious barrier constructed across a river valley to form a deep storage Reservoir is known as Dam. The surplus water is not allowed to flow over the dam, but it flows through the spillways provided at some designed level.
Book- Irrigation Engineering, Writer- N N Basak