Software for Custom Flume and Weir Staff Gages
This technology-development project will simplify the creation of discharge-graduated staff gages for weirs and flumes.
Weirs and flumes create a unique relationship between upstream head and discharge, embodied in a rating equation that computes discharge from measured head. Although many sites now use electronic water level sensors and telemetry equipment, there should always be a staff gage at each structure. These gauges would allow suspicious readings to be verified, and ditchriders and water users visiting a site to determine flow rate by direct visual observation.
Traditionally, staff gages have shown upstream head, and the user determined the flow rate by calculation or using a lookup table. More recently, the WinFlume software for long-throated flumes has allowed the creation of gages that show discharge directly. This project will extend this capability to other types of flumes and weirs, taking advantage of new technology available in the computer and sign-making industries.
Need and Benefit
Weirs and flumes create a unique relationship between upstream head and discharge. A formula derived from lab or computer calibration computes discharge from measured head. Although many sites now use electronic water level sensors and telemetry equipment, there should always be a staff gage at each structure. The staff gage allows easy verification of suspicious readings (sensors are not always perfect), and it allows a ditchrider visiting a site to determine the flow rate by direct visual observation.
Traditionally, staff gages have shown the upstream head, and the ditchrider determined the flow rate by calculation or through the use of a lookup table. These processes are prone to human error. More recently, the WinFlume software for long-throated flumes has allowed the creation of gages that show discharge directly. When WinFlume was originally written, staff gages were created by plotting a full-size image of the staff gage onto one or more sheets of paper. If the gage was large, the separate pages had to be reassembled after printing. The gage image was then provided to a sign maker who "copied" it onto a durable medium, such as baked enamel on steel. The process was tedious, and there were several chances for errors to affect the end product, including printer calibration issues and inaccuracies in reassembling multi-page staff gage printouts.
Today, sign makers use computer-operated equipment and can create custom staff gages from electronic PDF files. This saves the end user of WinFlume from having to calibrate printers, print gages, and reassemble printouts. The user simply installs a PDF print driver (Adobe Acrobat, or one of many freeware and shareware alternatives), and prints the gage to that driver, which creates an electronic image of the staff gage. In most cases, a custom paper size can be defined in the driver so that the gage is fully contained in a single electronic file. Sign makers can produce gages at lower cost and with better accuracy when they work directly from the electronic image of the gage. Also, gage formats can be customized beyond the capabilities of WinFlume, if desired.
Unfortunately, this capability is only available for structures that can be designed and calibrated with WinFlume, namely long-throated flumes and broad-crested weirs. V-notch, Cipoletti, and rectangular sharp-crested weirs, Parshall flumes, and many other commonly encountered flumes and weirs cannot be accommodated. Although there are often good reasons to replace these structures with modern long-throated flumes, there are also many situations in which the existing structures are working satisfactorily, and the added convenience of a new discharge-graduated staff gage is not and should not be sufficient justification for replacement of an entire measurement structure.
This project will extend the capability for creating discharge-graduated staff gages from PDF files to all types of flumes and weirs. This will allow districts to make better use of existing infrastructure and will lead to more accurate, effective, and economical measurement of flow rate, which promotes the conservation and wise and efficient use of water.
Bureau of Reclamation Review
The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.
Wall Gage Creator software home page (final, PDF,
By Tony Wahl
Publication completed on October 17, 2008