WEIR IS A STRUCTURE TO STORE WATER .AND WATER RAISES ABOVE 
WEIR  LEVEL IT OVERFLOW DUE TO GRAVTY.NO REQULATION OF 
WATER IN THIS STRUCTURE.
iN BARRAGE WATER IS STORED AND REQULATED FOR IRRIGATION AND 
POWER GENERATION THROUCH GATES.

weir is an impervious barrier .here water level is rise up 
to the required hight & the surplus water is allowed to 
flow over the weir...........but in case of barrage 
adjustable gates are installed...........

WEIR: 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.