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Accurate measurement of irrigation water consumption in small channels is an important link in achieving reasonable irrigation area management and agricultural water pricing and improving agricultural irrigation water use efficiency. Fixed water measuring flumes have a high construction cost and are prone to causing local channel sedimentation, compromising the safety of channel water transmission and flow measurement accuracy. Portable water measuring flumes can be used repeatedly in channels within a certain contraction ratio, and the duration of one water measurement is short (generally less than 5 min), which will not cause sedimentation. A new portable primary and subsidiary fish-shaped flume has been proposed by dividing 1 fish-shaped cylinder into 3. The flow measurement and hydraulic performance of measuring flumes with different contraction ratios in a U-shaped channel under different working conditions were studied using prototype experiments and numerical simulation. Compared to the existing portable flume, the primary and subsidiary fish-shaped flumes have achieved high flow measurement accuracy, a large critical submergence degree, a low backwater height, and low head loss. The head loss can be reduced by selecting a suitable length-width ratio and column spacing distance. • A new portable primary and subsidiary fish-shaped flume is designed for canal flow measuring. • Compared with the previous single-cylinder measuring flume, the number of cylinders is increased to 3 in this paper, and the number of flow channels is increased to enhance the flow capacity. • The suitable range of the length-width ratio and the distance between the measuring cylinders of the measuring flume are studied to reduce energy loss. [ABSTRACT FROM AUTHOR]