According to Manning's formula, the discharge through an open channel is (where M = Manning's constant)
A × M × m1/2 × i2/3
A × M × m2/3 × i1/2
A1/2 × M2/3 × m × i
A2/3 × M1/3 × m × i
A × M × m1/2 × i2/3
A × M × m2/3 × i1/2
A1/2 × M2/3 × m × i
A2/3 × M1/3 × m × i