Parshall Flume Discharge Corrections: Wall Staff Gauge and Centerline Measurements

Abstract

Parshall flumes were developed in the early 1900s as a simple and inexpensive way to provide accurate flow measurement in open channels. Unfortunately, many Parshall flumes in use today do not follow essential design parameters that prevent them from accurately measuring flow. Two design parameters that are commonly overlooked are: the need to measure upstream head in the correct location and the need to have appropriate entrance wingwalls attached to the flume. With recent advancements in computational fluid dynamics (CFD), numerical modeling has made it possible to accurately model nonstandard Parshall flume designs of varying sizes without extensive financial commitments for physical modeling. This paper utilizes numerical modeling to create a correction procedure for 2–8-ft nonstandard Parshall flumes. Basic background information regarding Parshall flumes and the numerical model used are presented. In addition, the results and correction procedures determined when head measurements are taken at any location (other than the standard design location) on the converging wall or along the longitudinal centerline of the flume with either standard or nonstandard entrance wingwalls.