Parshall Flume Equations for Open Channel Flow Rate Calculations

Parshall flumes are used for open channel flow measurement, especially for flows containing suspended solids, like the flow into a wastewater treatment plant. Parshall flume equations can be used for flow rate calculations with either free flow or submerged flow through the Parshall flume. The flow through a Parshall flume is called free flow if the downstream water level is low enough that it doesn't interfere with the flow rate through the flume throat. The flow is said to be submerged if the downstream flow is high enough to interfere with flow through the throat. Parshall flumes must be constructed with specific dimensions as given in a table in this article.