Cipoletti / Rectangular Weir

Q = C L H^{3/2}

Sharp-crested rectangular and Cipoletti (trapezoid ~1:4 side slope) weirs discharge as C L H^{3/2}. H is the head on the crest measured upstream. Cipoletti side slopes compensate end contractions so L is the crest length without a contraction correction.

$Q$ (cfs or m³/s): Discharge
$L$ (ft or m): Crest length
$H$ (ft or m): Head on crest
$C$: Discharge coefficient

Step-by-step solved example

Cipoletti weir, C = 3.37 (US), L = 4.0 ft, H = 0.64 ft. Find Q.

Cipoletti / rectangular weir: Q = C L H^{3/2}.

1. H^{3/2}
0.64^{1.5} = 0.64 × √0.64 = 0.64 × 0.80 = 0.512.
2. Q
Q = 3.37 × 4.0 × 0.512 = 6.90 cfs.
$Q = 6.90 cfs$

Answer: 6.90 cfs

10 practice questions

0/10 correct

1.Q for a rectangular weir scales as

2.Cipoletti side slopes are about

3.Triangular 90° weir Q scales as

4.Head H is measured

5.If H doubles on a rectangular weir, Q multiplies by

6.L in Q = C L H^{3/2} is the

7.A suppressed rectangular weir has

8.C includes

9.Free nappe means

10.Submergence of a weir