What is a Parshall Flume and who invented it?

A Parshall flume has a special shaped open channel flow section which may be installed in a ditch ,canal, or lateral to measure the flow rate. The Parshall flume is a particular form of venturi flume and is named for its principal developer, the late Mr. Ralph L. Parshall (Water Measurement Manual, U.S. Bureau of Reclamation, 1984)."

Ralph L. Parshall saw problems with stream measurements when he began working for the USDA in 1915, as an irrigation research engineer. In 1922 he invented the flume now known by his name. When this flume is placed in a channel, flow is uniquely related to the water depth. By 1953 Parshall had developed the depth-flow relationships for flumes with throat widths from 3 inches to 50 feet. The Parshall flume has had a major influence on the equitable distribution and proper management of irrigation water



Parshall flumes are apparently the most widely used types of flumes now for fixed flow monitoring installations. They have wide flow ranges, resistance to submersion,and are simple to calibrate..
Parshall flumes are sized by throat width and conform to standardized dimensions published in the U.S. Department of the Interior, Bureau of Reclamation.

You can obtain more information from http://www.usbr.gov/wrrl/fmt/wmm/ which ASTM and ISO standards have also been written for them (ASTM, 1991; ISO, 1992 contains the Burea of reclamations water measurement manual.

Whole books have been written about Flumes and Weirs. Nowadays there are several types of popular flumes to choose from including the Palmer-Bowlus, Trapezoidal, HS/H/HL-Type, Cutthroat, RBC, Montana, and SANIIRI and plenty of custom flumes. Computer simulation software has been written to assist people in designing optimum flume types and computer assisted calculations assist many engineers (some of whom may not be aware of the technical implications) in designing Flumes and open channel equipment.