Primary Flow Signal”s Halmi Parshall Flume (PFS-HPF) flowmeter is designed for accurate measurement of open- channel flows in municipal water/wastewater facilities. The PFS-HPF flowmeter for open-channel flows handles excessive pipe slope or velocity conditions which can cause the traditional Parshall Flume to generate inaccurate measurements. The PFS-HPF open-channel flowmeter design is traceable to the U.S. National Institute of Standards and Technology, and also has a discharge coefficient that reduces environment-induced measurement errors. The self-supporting design of the PFS-HPF allows for a wider minimum to maximum flowrate range with the addition of secondary Primary Flow signal devices. With laboratory flow calibration, the PFS-HPF open-channel flowmeter”s accuracy is +/-1.0% of max rate, which is much lower headloss compared to the traditional Parshall flume.