How to Maintain Your Parshall Flume

Maintenance and inspection are periodically necessary to make sure a Parshall flume is operating correctly*

*correctly in this context is under free flow conditions

When inspecting a Parshall Flume there a couple things you’ll want to look out for:

  • Is the flume still level from front-to-back and from side-to-side?
    • For a Parshall flume to operate the way it should, the flume has to be level.  If the flume has been installed out of level or shifted over time it is usually best to correct the condition.  
    • While there are corrections available for these conditions, not correcting the issues adds complexity to getting the flow reading and can lead to otherwise correctable errors.
  • Is the flume in good condition?  
    • Are there any visible signs of deterioration?  In fiberglass deterioration is usually wearing down of the flume’s gel coat (smooth inner surface).  In galvanized steel rust is the concern - usually present where there are bends, welds, and where the water normally flows through the flume.  Deterioration is not usually a concern with aluminum Parshall flumes.
  • Is the flume still in dimension?  
    • Have the flume’s dimensions changed - possibly due to frost heave, cattle, or simple deterioration?  If the dimensions are out by more than 2% the matter will need to be address - there is no easy correction for an out of dimension Parshall flume.
  • Have the upstream / downstream channel conditions changed?
    • In nature few things are truly static.  Vegetation grows.  Water erodes.  Natural channels meander. 
    • Any of these can mean the the conditions that existed when the Parshall flume was originally installed may no longer exist.  Changes need to be accounted for, and if they have an impact in a flume’s accuracy, need to be addressed.