Regardless of type, the correct point of measurement in a flume is upstream of the throat of the flume.  For no flume type is the primary point of measurement in the throat.  

• For all but the largest sizes of Parshall / Montana flumes, the point of measurement is 2/3rds of the distance back from the begining of the throat.  
• For Palmer-Bowlus flumes, the closest the point of measurement is to the throat is D/2 upstream (D = flume size).  
• For the Cutthroat flume, the point of measurement is 2/9 of the lenght of the flume upstream of the throat.  
• For H flumes, the point of measurement is close to the entrance of the flume and varies by flume style (HS, H, HL).  
  • For HS flumes, the point of measurement is 0.5 D (D = flume depth) from the entrance.
  • For H flumes, the point of measurement is 0.3 D (D = flume depth) from the entrance.

  • For HL flumes, the point of measurement is 0.25 D (D = flume depth) from the entrance.

• For Trapezoidal flumes, the point of measurement is close to the entrance of the flume before the throat contraction. 
• For RBC flumes, the point of measurement is D/2 (D = flume size) upstream of the throat ramp.

Only in Parshall is any measurement taken in the throat, and that measurement, at the H_b location, is only for the determination of the submergence of the flume.

The discharge table for each flume includes a graphic showing the primary point of measurement for that particular flume.  Consult the relevant discharge table for additional information.