Abstract: Water-gauging facility in canals is of great significance to water saving and efficient and sustainable water utilization in irrigation districts. To research the gauging facility with simple structure, low head-loss, high accuracy, simple and clear discharge formula is one of the irrigation management techniques urgently needed in irrigation districts. A dummy airfoil-shaped water-gauging facility was brought forward. Systematic experiments on the U-shaped canals with 12 different contraction ratios for measuring flumes were conducted. The experiment results show that the flow through the flume is smooth, water head-loss is low and experimental data are closely correlated with the correlation coefficient R²=0.9988. The discharge formula established by the method of dimensional analysis is harmonious, and the formula fitted with exponential form is simple, clear and practical, the mean error of discharge calculating results is less than 3%, and critical submergence reaches 0.92.