Parshall Flumes and The USBR

USBR Water Measurement Manual - 3rd Edition Cover The USBR - U.S. Bureau of Reclamation (a part of the Department of the Interior) has long been a source of information on the Parshall Flume - particularly with their Water Measurement Manual (WMM).

Before the advent of the internet, the Water Measurement Manual was THE go-to guide when operators needed information on the flume, its dimensions, and application. Since then, the WMM simply hasn’t kept up with research in the application and use of the Parshall Flume - its last update being all the way back in 1997 - 22 years ago!

Overtime, the dimensions and flow equations for the Parshall Flume have been codified in ASTM D1941 and ISO 9826 - suplanting the WMM in this role (the ASTM standard being regularly updated).

While these standards provide only limited information on the applicaton of the Parshall Flume, sites like Openchannelflow.com provide the latest information on: proper upstream / downstream conditions, selecting the site, and installing the flume. Additionally, information on flow submergence, correcting for settling, and non-standard flume sizes is also available.

While the WMM presents basic information on the Parshall Flume, the USBR advocates the use of long throated flumes sized specifically for each site - something not practical for the vast majority of operators. While the WinFlume program developed by the USBR can be used to model these flume’s, the software was last updated in 2014 and runs on “Windows 95 (support for which ended in 2000) or newer” - making the program unavailable for users of current OS.

For many operators, the Parshall Flume remains an accurate and dependable method of measuring water rights, irrigation flows, industrial discharges, and wastewater flows.