Rectangular Weir Flow Rate Calculation  

Where,
q = Flow Rate
C_{d} = Discharge Constant
b = Width of the Weir
g = gravity (9.81 m/s^{2})
h = Head on the Weir
Example:
Calculate the Rectangular Weir Flow Rate for the given details.
Head on the Weir (h) = 25 m
Width of the Weir (b) = 20 m
Discharge Constant (C_{d}) = 15
Solution:
Apply Formula:
q = 2/3 ×C_{d} ×b × (2g)^{1/2} ×h^{3/2}
q = 2/3*15*20*(2*9.81 m/s^{2})^{1/2*}25^{3/2
}Flow Rate =110736.17295175052 m^{3}/s