Montana Flume Flow Corrections under Submerged Flow

Abstract

A Montana flume is a Parshall flume without a diverging downstream section and is used to measure open channel flow. Under free-flow conditions, the Parshall flume and the Montana flume have the same calibration characteristics, but under submerge flows, their calibrations significantly differ. Tests were conducted at the Utah Water Research Laboratory on an acrylic 15.2-cm (6-in.) Montana flume to determine the effects of submergence on the flow readings. This type of investigation has not been previously analyzed. It was found that a standard Parshall flume rating curve overpredicted flow rates in the submerged Montana flume, up to 48%. Parshall submergence corrections were applied to the submerged Montana flume, and flow rates were underpredicted by up to 19%. This study has developed submerged flow rate correction factors specifically for a Montana flume, and the paper also demonstrates how to apply the corrections.