The discharge over a rectangular weir, considering the velocity of approach, is (whereH1 = H + Ha = Total height of water above the weir, H = Height of water over the crest of the weir, and Ha = Height of water due to velocity of approach)
(2/3) Cd × L.√2g [H1 - Ha]
(2/3) Cd × L. √2g [H1 3/2 - Ha 3/2]
(2/3) Cd × L.√2g [H1 2 - Ha 2]
(2/3) Cd × L. √2g [H1 5/2 - Ha 5/2]
