Unification of Parshall Flume Data

The Parshall critical depth flume has been used extensively in the Western United States and other parts of the world since about 1925 and is accepted as a standard measuring device in open channel irrigation. The original design, which was somewhat empirical, has been maintained until now; also the results have been presented as a number of empirical formulae covering widths ranging from 1 in. to 50 ft. For these reasons engineers have hesitated to use sizes of flumes other than those specified and have felt that great care must be taken to build the flumes according to the dimensions given. In this paper, dimensional methods have been used to develop a semi-theoretical equation relating flow and depth for all flumes from 1 in. to 50 ft. Excellent agreement between this equation and all published data is found. This will permit using flumes of non-standard sizes and will broaden the field of application for this type of measuring device.