The Cutthroat flume was designed to measure flow to an accuracy of +/-3%. As with any flume, however, properly installed, total site accuracy is usualy +/-10%.
Note that this accuracy is to be expected only when the ratio of flow depth (at the point of measurement) to flume length is between 0.1 and 0.4 (0.1 < H/L 0.4).
Above 0.4 and higher approach velocities and rapid changes in the water surface introduce inaccuracies.
As a result, extended sidewalls should only be used on Cutthroat Flumes to gain additional flow capacity as a last resort.
Image: Montana Water Commissioners Training
