The correct answer is (a) 120 cumecs
The best explanation: The discharge over the weir without any velocity of approach is given by –
Q = C.L H^3/2 where C = 1.66 when the width of rectangular crest > 0.9 m, L is the length of the weir and H is the head of water over the weir.
Q = 1.66 x 55 x 1.23/2 = 120 cumecs.