Generalised stage-discharge relationship for rectangular weirs

Rectangular weirs, which are very common hydraulic structures used in irrigation channels as water measuring devices, can be used for measuring very small discharges as well as high flow rates. From the practical point of view the availability of a unique stage-discharge formula that can be applied for the different types of the rectangular weirs would be of great practical importance. At first, in this paper the Buckingham’s Theorem of the dimensional analysis and the self-similarity theory are used to deduce the stage-discharge curve of different kinds of rectangular weirs such as slit and partially contracted ones. Then the proposed formula is calibrated using both the experimental data available in the literature and the measurements carried out in this investigation. Comparing with the available stage-discharge relationships, the results indicated that the proposed method can be used for the entire range of the ratio of the weir width to the channel width, i.e. both slit and partially contracted weirs, with acceptable accuracy.