Irrigation in the Pacific Northwest

Rectangular Submerged Orifices

This calculator determines the flow rate of water through a rectangular submerged orifice. This is underwater rectangular hole that water goes through. The water level on the upstream side is higher than the water level on the downstream side. Learn more about the units.


Rectangular Orifice Cross Sectional Area:
Upstream-downstream Height Difference or Change:
Flow Rate:


The Equation

The equation to determine the flow rate for a Rectangular Submerged Orifice is:


= Flow Rate through the orifice (cfs).

= The cross sectional area of the open rectangular orifice in square feet (height x width).

= Height (elevation) difference between the upstream and downstream still water surfaces.


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