Irrigation in the Pacific Northwest

Parshall Flume

This calculator finds the flow rate through a Parshall Flume. A Parshall flume has particular dimensions. It can be identified by both a section that has a contraction in the width of the flume as well as a dip in the elevation of the bottom of the flume. The height change is the difference in height between the upstream and downstream water elevations. Learn more about the units used on this page.


Throat Width:
Height Change:
Flow Rate:


The Equations

The Equations used to determine the flow rate vary depending on the throat width of the flume.

For 3 in throat width use

For 6 in throat width use

For 9 in throat width use

For 1 ft throat width use

For 2 ft through 8' throat width use

For 10 ft through 25 ft throat width use


= Flow Rate in cfs

= Height in feet

= Throat width in feet

WSU Prosser - IAREC, 24106 N Bunn Rd, Prosser WA 99350-8694, 509-786-2226. Contact Us