Unified Rating Equations for Cutthroat Flumes Derived from a Three-Dimensional Hydraulic Model

A sophisticated mathematical model of three-dimensional hydraulics was used to develop complete calibrations for Cutthroat flumes, which are structures used in canals (or “open channels”) to measure flow rates. Although Cutthroat flumes have been used for many years, and much research has been done on their calibrations and application in the field, never before was there a complete set of calibration parameters for all 24 standard flume sizes. This research was validated by previously published laboratory results on prototype flumes at Utah State University and elsewhere, and it was successful in generating accurate calibration parameters for all 24 flume sizes, plus all intermediate sizes. Thus, the results can be applied in general, with no loss in flow measurement accuracy for even the best previous calibration findings. Furthermore, the calibration equations produced as a result of this research do not depend on the distinction between free- and submerged-flow regimes, which has been a source of confusion and error in many field applications of these (and other) flumes.With these new calibration results, flow measurement in irrigation and other canals is more convenient, accurate, and straightforward than ever before. This is important because flow measurement is critical for evaluating water management, verifying compliance with legal and environmental concerns, and in implementing operational plans for irrigation systems and other open-channel water delivery and or removal systems.