The discharge over a rectangular weir, considering the velocity of approach, is (where H1 = Total height of water above the weir = H + Ha H = Height of water, over the crest of the weir, and Ha = Height of water, due to velocity of approach)

• Cd x L2g [H1 - Ha]
• Cd x L2g [H13/2 - Ha3/2]
• Cd x L2g [H12 - Ha2]
• Cd x L2g [H15/2 - Ha5/2]