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 is measured in the approach section of the flume from the bottom of the flume. It assumes that the flume is free flowing (water exits the flume freely) and not submerged (downstream water isn't backed up into the flume). Submerged flumes have to use different tables or calculator. Learn more about the units used on this page.

 

Throat Width:

3" 6" 9" 12" 2 ft to 8 ft 10 ft to 25 ft

Width:

ft in cm m

Height:

ft in cm m

Flow Rate:

cfs gpm lps

 

The Equations

The Equations used to determine the flow rate vary depending on the throat width of the flume. (U.S. Bureau of Reclamation Water Measurement Manual. 1993)

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

Where:

= Flow Rate in cfs

= Height in feet. Measured in the approach (upstream) portion of the flume from the bottom.

= Throat width in feet