The hydraulic performance of large-diameter gated fluming, commonly used in furrow irrigation, was investigated using computational fluid dynamics (CFD). The continuity and the momentum equations governing the fluid in the system were solved numerically for a steady incompressible and turbulent flow using a realizable software model. The CFD results were compared with the laboratory measured results and those obtained using a hydraulic simulation model. The CFD results showed a good correlation with the measured data and those generated using the software. The velocity head in the pipeline had no influence on the magnitude of the outflows possibly due to the unique shape of the outlet. The pressure head recovery across the outlets was greater than the energy loss along the pipe; hence, the pressure and discharge increased towards the downstream end. The CFD approach was found to be an appropriate tool for detailed analysis of the hydraulic characteristics of gated irrigation pipelines.