Irrigation in the Pacific Northwest

Cipolletti (Trapezoidal) Weir

This calculator determines the flow rate for a Cipolletti weir, which is a commonly used weir in many irrigation districts. The weir opening has a flat bottom and sides that have a particular slope. The water before the weir should be held in a relatively calm and smooth pool. The length is found by measuring the bottom width of the Cipolletti weir. The height is measured from the water height above the bottom of the weir.

Learn more about the units used on this page.


Flow Rate:



The Equation

The equation to determine the flow rate for a Cipolletti (Trapezoidal) Weir is:


= Flow Rate in cfs.

= Width of the weir crest in feet.

= Height of the upstream water above the weir crest in feet.





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