Rectangular Cutthroat Flow Measuring Flumes

Introduction: Procedures and methods for more accurate measurement and improved management of water are continually being sought to make better use of our water resources. Of all the devices and structures developed for measuring water, measuring flumes are among the most widely accepted and used. The most common measuring flume is the Parshall flume developed by Ralph Parshall at Colorado State University. Common to most flumes is the basic geometry consisting of a converging inlet section, a throat, and a diverging outlet section. Occasionally, the diverging outlet section is removed under free flow conditions, and the water is allowed to jet directly from the throat section into the downstream channel. This is not always permissible, however, in unlined channels because of possible erosion problems. In flat gradient channels, a flume may be installed to operate under conditions of submerged flow rather then free flow in order to (1) reduce energy losses, and (2) allow placement of the flume on the channel bed to minimize the increase in water surface elevation upstream from the flume. The purpose of the research effort reported herein was to develop a flume which would operate satisfactorily under both free flow and submerged flow conditions