Calibrating a Parshall Flume

concrete parshall flume under construction One of the advantages of using a device like a Parshall Flume is that, properly installed and applied, there is NO NEED TO CALIBRATE THE FLUME!

Now that doesn’t mean that you don’t need to periodically check to make sure the Parshall Flume isn’t clean and level, or that the upstream / downstream conditions haven’t changed - because they do!

Generally, before the flow season begins, its recommended that you do a site inspection.

You’ll want to make sure:

The Parshall Flume hasn’t shifted out of position due to frost heave, animal traffic, or subsidence.
That the Parshall Flume’s flow surfaces are free of algae and other biological growth.
The Parshall Flume is still in dimension - within 2% of the nominal dimensions. Throat width is particularly important.

That the channel upstream and downstream of the Parshall Flume hasn’t changed and that vegetative growth isn’t impacting flow - particularly out. Maintenance may have to be performed to remove sediment and debris.

Verify that the channel hasn’t experienced overtopping since the last inspection.
If the flume has a staff gauge, take a look to make sure that gauge is readable - cleaning or replacing as necessary.
Finally, if there is a flow that is used with the flume, the location and calibration of that meter should be checked.

And that’s it!

Again, remember you are normally not calibrating the Parshall flume, simply making sure the conditions it operates in are still good!

Image: Mountain Scholar