The lack of a precise flow measurement device for terminal irrigation channel diversion often results in significant inaccuracies. To address this issue, a wide-bottom sill flow measurement device, the 'measurement-control integrated side sluice gate' (MCIS), was developed to facilitate accurate flow measurement. This study investigated the hydraulic characteristics and mechanism of lateral flow in the MCIS, including flow regimes, changes in water surface profiles and assessments of head losses. Discharge equations for the MCIS were then created via dimensional analysis and multiple nonlinear regression, and their accuracy was assessed and validated. The findings reveal that at high relative openings (e/H-1), the flow through the MCIS follows weir flow characteristics, whereas at low e/H(1 )ratios, it exhibits orifice flow behaviour. The transition point between these flow regimes, identified as the critical relative opening (e/H-1)(c), is 0.84. The overall accuracy of flow measurement using the MCIS gate structure is 4%, with the weir flow equation achieving an average accuracy of 1.4%, surpassing the accuracy of the rectangular sharp-crested side weir flow measurement equation by more than 2.5 times. Similarly, the average accuracy of the orifice flow equation is 4%, which is 1.1 times higher than that of the rectangular spire side orifice.
