Calibrating the discharge of the Kut Barrage using related equations at different gates openings

The Kut Barrage is one of the most important hydraulic structures in Iraq, which is in place to regulate the flow from the Tigris River and distribute it between Graf River, Dujelah Channel, Dalmch Channels, and other irrigation projects. The barrage includes 56 sluice gates, each 6 m wide, which control the discharge of the Tigris River at the individual locations. According to observations and measurements, about 90% of the flow at the downstream has been modular (free flow) within the last five years. In the present study, a trial was attempted to calibrate some universal formulas that would offer a reliable means of determining the discharge under gates such as those presented by Rajaratnam and Subramanya, Swamme, and Ferro, which would make them suitable for Kut Barrage discharge calculation over a wide range of scenarios in terms of gate openings. A recent formula presented by Maatooq for canal operation was also adopted in order to test whether it was appropriate for application under the flow and geometric boundary conditions of the Kut Barrage. The available data was also used to extract an empirical equation for the coefficient of discharge used for calibration. A total of 221 measurements taken at the head at upstream, nine different gate openings, and at the discharges were employed for calibration, and 28 data points taken at six different gate openings were adopted for verification. The determined discharges using the calibrated formulas show good agreement with the measurements with the coefficient, R² ranging between 0.874 using Rajaratnam and Subramanya and 0.880 using Maatooq. (paper)