The discharge through a wholly drowned orifice is given by (where H1 = Height of water (on the upstream side) above the top of the orifice, H2 = Height of water (on the downstream side) above the bottom of the orifice, and H = Difference between two water levels on either side of the orifice)

• Q = Cd x bH1 2gh
• Q = Cd x bH2 2gh
• Q = Cd x b ( H2 - H1 ) 2gh
• Q = Cd x bH 2gh