Isn the Parshall flume more accurate than other types of flumes like the Palmer Bowlus?
This is a persistent myth, the Parshall is better known than some of the other flume types and has a wider apparent range than flumes like the Palmer Bowlus. The wider apparent range is somewhat misleading and invites an apple and oranges type of comparison. The Parshall is intended for use in a truly open channel. On the other hand the Palmer Bowlus flume is designed to be used with a closed pipe that is flowing partially full. The range of the Palmer Bowlus is therefore limited by the capacity of the pipe. In situations where Parshall flumes are to be installed in channels fed and drained by closed pipes there range is also limited by the pipes capacity. Generally one flume is no more accurate than another is. The narrow throat section of a flume will produce a predictable change in depth in the upstream portion of the flume provided that the energy present in the flow stream is less than the energy threshold of the throat of the flume. Since energy is conserved it is possible to pre
